Unit 1

Question 1

Define thermal transmission.

Answer 1

The quantity of heat flow from all mechanisms, in unit time, under prevailing conditions

Heat energy moves from a warmer source to a cooler source.

Question 2

Define thermal conductivity (k).

Answer 2

The thermal heat flow, by conduction only, through a unit thickness of a single uniform type of material

Units are (W/mK)(Btu-in/h•ft2.°F).

Question 3

What is the definition of thermal resistivity (RU)?

Answer 3

The reciprocal of thermal conductivity

Units are (mK/W)(hoft2.°F/Btuoin).

Question 4

Define thermal conductance (C).

Answer 4

The thermal heat flow through a unit area of a non-uniform, composite material when a unit average temperature difference is established

Units are (W/m2K)(Btu/h•ft2.°F).

Question 5

Define thermal transmittance or U-factor (U).

Answer 5

The thermal heat flow through unit areas of a wall, door, window, etc., for every degree temperature difference

Units are the same as for thermal conductance (W/m2K)(Btu/h•ft2.°F).

Question 6

What are the two major types of heat gains?

Answer 6

• External heat gains
• Internal heat gains

Heat gains must be calculated to estimate the total cooling load.

Question 7

What is the principle behind heat movement?

Answer 7

Heat always moves from a warmer source to a cooler source

This principle is fundamental in understanding heat gains.

Question 8

Name the components included in external heat gains.(4)

Answer 8

• Conduction
• Infiltration
• Ventilation
• Solar radiation

These components contribute to the heat entering an air-conditioned space.

Question 9

What assumption is made regarding conduction heat gains?

Answer 9

The temperature of the outer surface of the building is the same as the outdoor design condition

This does not include additional heat from solar radiation.

Question 10

What factors are important when calculating conduction heat gains?(3)

Answer 10

• Construction details of walls and roof
• Types of windows and doors
• U-factor values of each component

These factors affect the amount of heat flow through the building.

Question 11

What does the amount of heat flow through a construction depend on?(3)

Answer 11

• Overall resistance of materials
• Thermal conductivity
• Temperature difference between inside and outside surfaces

Higher resistance results in less heat flow.

Question 12

What are the internal heat gains in a building?(5)

Answer 12

• People
• Lighting
• Electric motors
• Appliances
• Cooking

Internal heat gains contribute to the overall heat load in a conditioned space.

Question 13

The heat load due to people in a building is in the form of what types of heat?(2)

Answer 13

• Sensible heat
• Latent heat

Latent heat is contained in the water vapor released through perspiration.

Question 14

How is the heat gain from incandescent lighting fixtures calculated?

Answer 14

By adding the wattage rating of each fixture

The heat gain from lighting is primarily dependent on wattage rather than room temperature.

Question 15

How can heat gains from lighting be reduced?

Answer 15

By recessing the fixtures to minimize heat entering the room

This design choice can help manage internal heat loads.

Question 16

What type of heat do electric motors give off while running?

Answer 16

Sensible heat

The heat equivalent of the motor load must be removed by the cooling equipment.

Question 17

What types of appliances contribute to internal heat gains?

Answer 17

• Cooking equipment in restaurants
• Devices like hair dryers and clippers in beauty parlors

These appliances must be accounted for in heat gain calculations.

Question 18

What is the estimated heat gain from cooking equipment installed in a conditioned space without a hood?

Answer 18

50% of the equipment’s output

Of this, approximately 66% is sensible heat and 34% is latent heat.

Question 19

What happens when the outdoor temperature is below the temperature inside a building?

Answer 19

Heat will escape from the building

The lower the outdoor temperature, the more heat will escape.

Question 20

To maintain comfortable conditions inside a building, heat loss must be replaced by the ________.

Answer 20

heating system

Keeping heating costs low requires minimizing heat losses.

Question 21

Name the three methods by which heat is lost from a building.

Answer 21

• Conduction
• Convection
• Radiation

These methods describe how heat escapes from warmer inner surfaces to cooler outer surfaces.

Question 22

Heat is conducted through building walls, ceilings, and floors from the warmer inner surfaces to the ________.

Answer 22

cooler outer surfaces

This process is essential in understanding how heat loss occurs.

Question 23

What occurs to warm room air near cooler outside walls and ceiling?

Answer 23

It gives up some of its heat and becomes heavier

This process leads to convection currents and heat loss by convection.

Question 24

When you stand close to an outside wall in winter, your exposed arm may feel cold due to heat movement by ________.

Answer 24

radiation

This illustrates how warmer objects radiate heat to colder surfaces.

Question 25

How can heat losses be reduced significantly?(2)

Answer 25

* Adding layers of insulation (fibreglass or Styrofoam) * Installing extra panes of glass in windows ## Footnote Insulation helps maintain indoor temperatures and reduces heating costs.

Question 26

What is **infiltration** in the context of heat loss from buildings?

Answer 26

The leakage of air into and out of the building ## Footnote Most air leakage occurs around windows and doors.

Question 27

How can infiltration be reduced?

Answer 27

* Caulking around frames * Weather-stripping doors and windows ## Footnote These methods help minimize air leakage and heat loss.

Question 28

Why is a certain amount of fresh air required in buildings?

Answer 28

To provide ventilation and prevent excessive moisture build-up ## Footnote This is essential for maintaining indoor air quality.

Question 29

What effect does ventilation have on the heating system?

Answer 29

It puts an extra load on the heating system ## Footnote Ventilation requires heating the cold fresh air that enters the building.

Question 30

The amount of heat lost by conduction, convection, radiation, and infiltration is directly affected by **________**.

Answer 30

wind velocity ## Footnote Stronger winds increase heat loss from buildings.

Question 31

What is the purpose of an **Air Vent** in steam heating systems?

Answer 31

To allow for removal of air from piping, radiators, and convectors ## Footnote This is necessary to make way for the steam during normal operation.

Question 32

Define **Condensate** in the context of steam heating.

Answer 32

Water formed when steam gives up its heat energy ## Footnote In heating systems, condensate is usually returned to the boiler to be converted to steam again.

Question 33

What is the function of a **Radiator Trap** or **Steam Trap**?

Answer 33

Allows condensate to be discharged from the radiator while preventing steam from discharging ## Footnote This is essential for maintaining efficiency in heating systems.

Question 34

Describe the basic operation of a **steam heating system**.

Answer 34

Steam is generated in a boiler, circulated through pipes to radiators, gives up heat, condenses to liquid, and returns to the boiler ## Footnote This cycle allows for efficient heating of larger buildings.

Question 35

What types of heating systems are commonly used for residential buildings?(2)

Answer 35

* Hydronic (hot water) systems * Warm air heating systems ## Footnote These systems are typically used in smaller commercial buildings as well.

Question 36

What are **heating equipment** or **heating accessories**?

Answer 36

Parts of a heating system apart from the boiler and its fittings ## Footnote Includes radiators, convectors, traps, air vents, and pumps.

Question 37

What materials were older **radiators** typically made from?

Answer 37

Cast iron ## Footnote Older radiators were built in sections connected by screws or push nipples.

Question 38

What are the three classifications of **radiators**?

Answer 38

* Floor type * Window type * Wall-hung ## Footnote Each type is designed for specific installation needs.

Question 39

How do **convectors** differ from traditional radiators?

Answer 39

They use metal fins to increase heat transfer from the pipe to the air ## Footnote Convectors have largely replaced cast-iron radiators in modern installations.

Question 40

What is the construction feature of a **convector**?

Answer 40

A pipe enclosed in a metal cabinet with grill-type openings ## Footnote This design facilitates natural circulation of air through the convector.

Question 41

What is the process called when air circulates naturally without the aid of a fan?

Answer 41

convection air currents ## Footnote Cool air enters at the bottom and rises as it is heated by contact with the warm cabinet surface.

Question 42

Where should **radiators and convectors** be placed for optimal performance?

Answer 42

Against outside walls, especially under windows ## Footnote This placement allows warm air to mix with cold air coming down from cooler surfaces above.

Question 43

What happens if the **cabinet cover** of a wall convector rests on the flooring?

Answer 43

It will not circulate the heated air ## Footnote There must be room below the cabinet cover for cooler air to enter.

Question 44

What must the **wall convector piping** be graded down towards?

Answer 44

The direction of flow for the condensate ## Footnote This ensures proper drainage and collection at the steam trap.

Question 45

What is a **unit heater**?

Answer 45

A convector heater that employs a blower or fan ## Footnote It forces air through the heating coil instead of using natural circulation.

Question 46

What is the advantage of using a **unit heater**?

Answer 46

It results in a large heat output ## Footnote This is achieved for a fairly compact unit.

Question 47

What type of **unit heaters** can be mounted on the floor, wall, or suspended from the ceiling?

Answer 47

Cabinet units ## Footnote They can also discharge air horizontally.

Question 48

What is the purpose of **horizontal discharge unit heaters**?

Answer 48

Used for heating large spaces, such as warehouses and commercial buildings ## Footnote They are typically ceiling suspended.

Question 49

Where is the **steam piping connection** made on a horizontal unit heater?

Answer 49

To the top of the horizontal unit heater ## Footnote This allows condensate to drain to the bottom where the steam trap is located.

Question 50

What do **fin coils/reheat coils** do in larger buildings?

Answer 50

Increase the rate of heat exchange ## Footnote They consist of one or more rows of heated fin coil/reheat oil placed across the air duct.

Question 51

How is **individual room temperature** controlled in a heating system?

Answer 51

By dampers that regulate the amount of heated air passing into each room ## Footnote This allows for tailored heating in different spaces.

Question 52

What are **unit ventilators** also known as?

Answer 52

Univents ## Footnote They are cabinet-type unit heaters equipped with additional features for ventilation.

Question 53

What components are included in a **unit ventilator**? (5)

Answer 53

* Standard heating coil * Blower or fan * Air filter * Dampers * Outside air inlet ## Footnote These components work together to provide heating and ventilation.

Question 54

In a unit ventilator, what happens when the room temperature is below the thermostat setting?

Answer 54

The mixing damper prevents outside air from entering while keeping the room air inlet wide open ## Footnote This ensures all air discharged by the fan passes through the heating coil.

Question 55

What occurs when the room temperature approaches the thermostat setting in a unit ventilator?

Answer 55

The mixing damper opens the outside air intake slightly and reduces room air intake ## Footnote This allows part of the air mixture to bypass the heating coil.

Question 56

What is the function of the **bypass damper** in a unit ventilator?

Answer 56

Regulates the amount of air passing through the heating coil ## Footnote It works in conjunction with the mixing damper to control air flow.

Question 57

When room temperature exceeds the thermostat setting, what does the mixing damper do?

Answer 57

Admits a maximum amount of outside air and a minimum amount of room air ## Footnote This helps to cool the room by reducing heating.

Question 58

What feature do unit ventilators often have to control air flow?

Answer 58

Three-speed switches ## Footnote These switches regulate the speed of the fan.

Question 59

How did older steam heating systems vent air?(2)

Answer 59

* Manually operated vent valves * Small petcocks on convectors and heaters ## Footnote These valves were opened during start-up and occasionally during operation to remove air.

Question 60

Describe the function of a **modern automatic air vent**.

Answer 60

Expels air from the system and closes tightly when filled with steam ## Footnote It consists of a sealed cylinder with a needle valve and a flexible diaphragm.

Question 61

What happens to the needle valve in an automatic air vent when hot steam surrounds the cylinder?

Answer 61

The needle valve closes to prevent steam escape ## Footnote This occurs due to increased pressure from the evaporating volatile liquid.

Question 62

What condition causes the needle valve in an air vent to reopen?

Answer 62

When air collects again and the vapor in the cylinder condenses ## Footnote This results in a pressure drop, allowing the valve to open.

Question 63

What are the consequences of air in a steam heating system? (3)

Answer 63

* Blocks steam flow * Reduces heat transfer * Promotes corrosion ## Footnote Air must be removed for efficient operation of the heating system.

Question 64

How did older steam heating systems vent air?(2)

Answer 64

* Manually operated vent valves * Small petcocks on convectors and heaters ## Footnote These valves were opened during start-up and occasionally during operation to remove air.

Question 65

What type of trap is commonly used in steam heating systems?

Answer 65

Thermostatic trap ## Footnote Thermostatic traps can have either corrugated bellows or a disc design.

Question 66

What are the two designs of **manually operated radiator valves**?

Answer 66

* Straight-through design * Angle design ## Footnote These valves control the flow of steam to the radiators.

Question 67

What is the function of a **packless radiator valve**?

Answer 67

Prevents steam from leaking around the valve stem ## Footnote It uses a bronze diaphragm to seal off the valve body.

Question 68

How does a **packless radiator valve** operate?

Answer 68

The button pushes down against the diaphragm, closing the valve disc against its seat ## Footnote When the stem is backed off, the spring lifts the disc off its seat, opening the valve.

Question 69

What is the role of a **condensate receiver** in steam heating systems?

Answer 69

Collects condensate discharged by steam traps ## Footnote It drains by gravity through return piping to a condensate pump.

Question 70

What controls the operation of a **condensate pump**?

Answer 70

Float switch on the receiver ## Footnote The pump pushes water from the condensate receiver to the steam boiler as needed.

Question 71

True or false: The **condensate receiver** is vented to atmosphere.

Answer 71

TRUE ## Footnote This ensures that the pressure in the receiver and return piping is at atmospheric.

Question 72

What is the primary function of a **vacuum pump** in steam heating systems?(2)

Answer 72

* Creates and maintains a vacuum in the return piping * Returns the condensate back to the boiler ## Footnote The vacuum pump assists condensate flow and reduces backpressure in large buildings.

Question 73

In large steam heating systems, what does the vacuum pump help to reduce?

Answer 73

Backpressure ## Footnote This reduction allows condensate to flow more easily to the condensate tank.

Question 74

What initiates the operation of the **vacuum pump** in the condensate return system?

Answer 74

Float switch ## Footnote The float switch activates the pump when the water in the accumulator tank reaches a predetermined level.

Question 75

What does the **exhauster** do in the vacuum pump system? (3)

Answer 75

* Forces water through nozzles * Creates a vacuum * Draws air, water, and water vapour from the accumulator tank ## Footnote The exhauster helps to increase the vacuum by condensing water vapour with the water passing through the nozzles.

Question 76

What happens to the air in the **air separating tank**?

Answer 76

It leaves through a vent to the atmosphere ## Footnote The water collects below in the air separating tank.

Question 77

What occurs when the water level rises in the air separating tank?

Answer 77

The discharge valve in the boiler feedline opens ## Footnote This allows excess water to be pumped to the boiler.

Question 78

What are the **types of piping arrangements** for steam heating systems?(8)

Answer 78

* One-pipe gravity return system * Two-pipe gravity return system * Two-pipe gravity steam system with steam traps * Two-pipe return trap system * Hartford loop * Two-pipe condensate pump system * Two-pipe vacuum return system * Two-pipe with variable vacuum system ## Footnote These arrangements define how steam and condensate are managed in heating systems.

Question 79

What is the **one-pipe gravity return system** also known as?

Answer 79

air vent system ## Footnote This system uses a single main for both steam supply and condensate return.

Question 80

In a **one-pipe gravity return system**, how does condensate return to the boiler?

Answer 80

By gravity through a single connection ## Footnote All piping is sloped downward to facilitate free flow of condensate.

Question 81

What is the main disadvantage of the **two-pipe gravity return system**?

Answer 81

Steam could pass through a radiator without condensing ## Footnote This could lead to air trapping in other radiators via the return main.

Question 82

What does the **two-pipe gravity steam system with steam traps** improve upon?

Answer 82

It isolates the steam main from the condensate return main ## Footnote This system addresses issues with steam entering the condensate return piping.

Question 83

In a **two-pipe return trap system**, where is the boiler typically placed?

Answer 83

Well below the lowest radiator or convector ## Footnote This placement is necessary to obtain sufficient static head for returning condensate.

Question 84

True or false: The **two-pipe gravity return system** operates at pressures from 0 to 103 kPa (15 psi).

Answer 84

TRUE ## Footnote This system uses separate steam and condensate return mains.

Question 85

What is the purpose of the **Hartford Loop** in steam heating systems?

Answer 85

To prevent steam pressure from forcing boiler water back into the return line ## Footnote It ensures that the water level in the boiler remains above the safe minimum level.

Question 86

In smaller steam heating systems, where is the **condensate** piped?

Answer 86

To a common condensate return line or return main ## Footnote This line feeds the condensate directly back into the boiler by gravity.

Question 87

In larger steam heating systems, where is all the **condensate** returned?

Answer 87

To a common condensate receiver or tank ## Footnote From there, it is returned to the boiler by a boiler feed pump.

Question 88

What potential danger does the **Hartford Loop** address?

Answer 88

The danger of a boiler losing its water and exploding ## Footnote This could cause serious property damage and possible loss of life.

Question 89

In many **two-pipe heating systems**, why is it not possible to return the condensate directly to the boiler by gravity?(2)

Answer 89

* Insufficient static head in the return line * Inability to use gravity ## Footnote This limitation necessitates the use of a condensate pump system.

Question 90

How is the **pump** operated in a two-pipe condensate pump system?

Answer 90

Operated by a float control in the receiver tank ## Footnote It ensures the condensate is returned to the boiler at the same rate steam is produced.

Question 91

What must be used to prevent the re-entry of air into the system in a **vacuum return system**?

Answer 91

A vacuum pump ## Footnote The vacuum pump draws air and condensate from the accumulator tank.

Question 92

What type of **valves** are equipped on the radiators or convectors in a two-pipe vacuum return system?(2)

Answer 92

* Modulating valves * Thermostatic steam traps ## Footnote These valves help manage steam flow and condensate drainage.

Question 93

What is the purpose of **drip lines** in the steam heating system?

Answer 93

Equipped with steam traps to remove any condensate ## Footnote They are installed on steam risers and at the end of the steam main.

Question 94

What is the **design** of a **Two-Pipe with Variable Vacuum System** similar to?

Answer 94

Vacuum return system ## Footnote The operation differs as steam supply pressure varies with weather conditions.

Question 95

During severe winter conditions, the steam supply pressure to heating units is at least _______.

Answer 95

atmospheric ## Footnote This contrasts with the partial vacuum used during milder conditions.

Question 96

What should be inspected before starting a **steam heating system**?(6)

Answer 96

* Boiler condition * Current inspection certificate * Accessible pipelines * Valves * Strainers * Heating units ## Footnote A thorough inspection ensures safe operation.

Question 97

What is crucial for the safe operation of a steam heating system regarding condensate?

Answer 97

It must be returned to the boiler without delay or interruption ## Footnote Failure to do so can lead to low water levels in the boiler.

Question 98

What should be tested using approved procedures in a steam heating system?(3)

Answer 98

* Safety valve * Blowoff valve * Water gauge ## Footnote Testing ensures all passages are clear.

Question 99

What are the main sources of trouble in **radiators and convectors**?(2)

Answer 99

* Valves * Steam traps ## Footnote Regular maintenance is required to prevent leakage and ensure efficiency.

Question 100

What should be done if a radiator valve is not the packless type?

Answer 100

Repacked periodically ## Footnote This prevents leakage around the valve spindle.

Question 101

What happens if a steam trap is leaking?

Answer 101

Steam escapes into return lines ## Footnote This interferes with normal condensate flow and wastes heat energy.

Question 102

What should be kept free of dust in a steam heating system?

Answer 102

Radiators and convectors ## Footnote Dust accumulation can hinder performance.

Question 103

What is the primary mechanism of **gravity circulation systems** in hot water heating?

Answer 103

Natural convection due to the difference in density between hot and cooler water ## Footnote Gravity circulation systems rely on gravity to move water, which can lead to slow response times and difficulties in maintaining circulation.

Question 104

List the **disadvantages** of gravity circulation systems.(4)

Answer 104

* Large pipe sizes necessary * Difficult circulation to radiators on the same level as the boiler * Slow response to changes in heat demand * Maximum water temperature limited to approximately 77°C (171°F) ## Footnote These disadvantages can hinder the efficiency of heating systems.

Question 105

What is the main advantage of **forced circulation systems** over gravity systems?

Answer 105

Ability to use smaller pipes and establish positive circulation to all heating units ## Footnote Forced circulation systems respond more rapidly to changes in heating load.

Question 106

What are the **types of hot water heating systems**?(4)

Answer 106

* Series loop system * One-pipe system * Two-pipe direct return system * Two-pipe reverse return system ## Footnote Heating piping systems today are variations and/or combinations of these types.

Question 107

In a **series loop system**, how are the heating units connected?

Answer 107

Connected in series ## Footnote The water circulates from the hot water supply main directly through all the convectors to the return main.

Question 108

What is the **disadvantage** of a series loop system?

Answer 108

Individual convectors cannot be shut off ## Footnote Room temperatures can be regulated with dampers fitted on the convector casings.

Question 109

In the **one-pipe system**, how is the water supplied to each convector?

Answer 109

Tapped off the main ## Footnote The return from each convector is connected back to the main downstream from the supply connection.

Question 110

What is a **disadvantage** of the one-pipe system regarding temperature?

Answer 110

Water entering each following convector is cooler ## Footnote This may require increasing the size of convectors toward the end of the system.

Question 111

How is **zone temperature control** achieved in the one-pipe system?

Answer 111

Installing thermostatically controlled valves on individual convectors ## Footnote This allows for better regulation of room temperatures.

Question 112

What are the two mains used in a **Two-Pipe Direct Return System**?

Answer 112

* Supply main * Return main ## Footnote This system connects convectors directly to the mains, allowing for a direct return of water to the boiler.

Question 113

In a **Two-Pipe Direct Return System**, how is the return flow described?

Answer 113

The first radiator fed is the first to return to the boiler, or the last radiator fed is the last to return to the boiler ## Footnote This indicates the flow path of water from the convectors back to the boiler.

Question 114

What is a challenge of the **Two-Pipe Direct Return System**?

Answer 114

Difficult to balance due to different circuit lengths ## Footnote Each convector may have varying lengths of water circuits, affecting flow equality.

Question 115

What is the main advantage of the **Two-Pipe Reverse Return System**?

Answer 115

All circuits have the same length ## Footnote This feature allows for self-balancing, ensuring equal water distribution to all convectors.

Question 116

In a **Reverse Return System**, how does the return flow differ from the direct return system?

Answer 116

The return from each convector takes the long way around to return to the boiler ## Footnote This design helps maintain equal flow and temperature across all convectors.

Question 117

What is the role of the **pump** in both the direct and reverse return systems?

Answer 117

Circulates water through the boiler and around the system ## Footnote The pump is located in the return line and discharges into the boiler.

Question 118

What type of **expansion tank** is used in the Reverse Return System?

Answer 118

Closed type, installed with an air separator ## Footnote This setup helps manage pressure and air in the system.

Question 119

What is a key feature of the **Reverse Return System** that simplifies installation in multi-storey buildings?

Answer 119

Pipe sizing is not as critical as in the direct return system ## Footnote This makes it easier to design and implement in larger structures.

Question 120

In a hot water heating system, where is the **circulating pump** located?

Answer 120

On the supply main near the boiler ## Footnote This positioning helps obtain maximum pressure in the supply main.

Question 121

What are the two types of **branch circuit arrangements** in hot water heating systems?

Answer 121

* Series loop system * Reverse return system ## Footnote The arrangement depends on the number of heating units in the branch circuit.

Question 122

How is the flow of water controlled in a **multi-zone hot water heating system**?(3)

Answer 122

* Each zone has its own circulating pump controlled by a thermostat * A single circulator with motorized valves for each circuit * A primary pump with secondary zone pumps controlled by thermostats ## Footnote These methods allow independent control of heating in different zones.

Question 123

What prevents **natural circulation** in a multi-zone system when the pump is not running?

Answer 123

Flow control valves ## Footnote These valves close to prevent overheating of that zone.

Question 124

What is the role of the **boiler** in a multi-zone hot water heating system?

Answer 124

Maintains the water temperature at the required setting ## Footnote It ensures that each zone can draw hot water as needed.

Question 125

What are the **advantages** of hot water heating compared to steam heating?(5)

Answer 125

* Temperature of supply water can be varied easily * Smaller and more compact boiler * Smaller pipe sizes and fewer fittings * Less critical piping pitch * Lower maintenance costs ## Footnote Hot water systems do not require traps and experience less corrosion.

Question 126

What are the **disadvantages** of hot water heating compared to steam heating?(5)

Answer 126

* Boiler must withstand high pressure in multi-storey buildings * Requires considerable power to circulate water * Greater danger of freezing damage * More damage from leaks * Must prevent air pockets in piping ## Footnote Air locks can block circulation in hot water heating systems.

Question 127

What is **radiant panel heating**?

Answer 127

Heating rooms using warmed sections of ceilings, walls, or floor panels ## Footnote It supplies heat mainly by radiation and a small part by convection.

Question 128

What are the **temperature limits** for radiant panel heating surfaces?

Answer 128

* Ceilings: not exceeding 46°C (115°F) * Walls: not exceeding 38°C (100°F) * Floors: below 30°C (86°F) ## Footnote These limits prevent discomfort and cracking of plaster.

Question 129

What is the maximum water temperature for **ceiling** and **floor** heating in radiant systems?

Answer 129

* Ceilings: not higher than 80°C (176°F) * Floors: not higher than 60°C (140°F) ## Footnote Lower temperatures are used to ensure comfort.

Question 130

What is the purpose of the **balancing fitting** in a panel heating system?

Answer 130

To obtain even heat distribution ## Footnote All panels are equipped with a balancing fitting.

Question 131

What temperature is typical for **boiler water** in a heating system?

Answer 131

Above 66°C (151°F) ## Footnote This temperature is too high for the flooring material.

Question 132

What is the function of a **mixing valve** in a panel heating system?

Answer 132

To temper the heated water before it reaches the panels ## Footnote This prevents damage to flooring materials.

Question 133

List the **advantages** of radiant panel heating over conventional heating systems.(3)

Answer 133

* More even heat distribution * More comfort for buildings on concrete slabs * Heating elements are out of sight ## Footnote These advantages enhance comfort and aesthetics.

Question 134

List the **disadvantages** of radiant panel heating systems.(3)

Answer 134

* Slow to heat up and cool down * Costly repairs for leaks * Difficult to make changes to the system ## Footnote These disadvantages can limit the system's effectiveness in certain buildings.

Question 135

What is the purpose of **snow melting systems** on driveways and sidewalks?

Answer 135

To eliminate snow removal and enhance safety ## Footnote These systems provide safer conditions for pedestrians and vehicles.

Question 136

How is the heat transfer solution heated in a **snow melting system**?

Answer 136

By steam or hot water supplied by the building's boiler ## Footnote The heated solution is circulated through coils in the sidewalk.

Question 137

What types of **snow melting equipment** are mentioned?(2)

Answer 137

* Electric resistance heating cables * Infrared radiant lamps ## Footnote These alternatives can be used for snow melting on surfaces.

Question 138

What is the recommended depth for **coils** in a sidewalk snow melting system?

Answer 138

At least 5 cm (2 in) below the surface ## Footnote This depth helps in effective snow melting.

Question 139

What type of solution is typically used in snow melting systems to prevent freezing?

Answer 139

Antifreeze solution (ethylene glycol) ## Footnote This is used when the system is not in operation.

Question 140

What are some **accessories** used in hot water heating systems?(10)

Answer 140

* Diverter fittings * Air vents * Air separators * Flow control valves * Balancing valves and fittings * Riser stop valves * Pressure reducing valves * Circulating pumps * Expansion tanks * Steam to hot water converters ## Footnote These accessories play crucial roles in the operation and efficiency of hot water heating systems.

Question 141

What type of system is no longer typically used in hot water heating installations?

Answer 141

One-pipe hot water system ## Footnote Diverter fittings were specifically designed for older one-pipe systems to ensure adequate water flow.

Question 142

What is the purpose of **diverter fittings** in hot water systems?

Answer 142

To ensure adequate flow of water through each convector ## Footnote Diverter fittings were essential in one-pipe systems to manage water flow effectively.

Question 143

What is the purpose of **supply and return type diverter fittings** in a hot water heating system?

Answer 143

The supply fitting restricts flow in the supply main and forces part of the water into the supply line to the convector ## Footnote The return fitting works in the opposite way.

Question 144

When filling a hot water system for the first time, where should air be vented?(3)

Answer 144

* Upper parts of the risers * Radiators * Convectors ## Footnote The system should be air-free at start-up except for air in the expansion tank.

Question 145

What happens to **dissolved air** in cold water when it is heated?

Answer 145

It is freed when the water is heated ## Footnote Air is also absorbed by cooler water in the expansion tank during operation.

Question 146

What type of air vent is commonly used in newer hot water heating systems?

Answer 146

Automatic air vents ## Footnote These are often float-operated and installed at the highest parts of mains and risers.

Question 147

Name two types of **manual air vents** used in hot water heating systems.

Answer 147

* Handwheel style * Coin-operated style ## Footnote These are used in areas where they are easy to access.

Question 148

What is the purpose of a **dip tube** in a hot water heating system?

Answer 148

To prevent air from leaving the boiler with the water ## Footnote The dip tube extends below the top of the boiler, allowing air to pass to the expansion tank.

Question 149

What should be done with the **air liberated** by heating the water in the boiler?

Answer 149

It should be trapped and directed to the expansion tank ## Footnote The air should not travel to parts of the heating system or be vented to the atmosphere.

Question 150

Name the **two methods** used to remove air from water in a hot water heating system.

Answer 150

* Allowing air to travel with the heated water * Using an air separator or air scoop ## Footnote These methods help ensure that air does not accumulate in the system.

Question 151

What type of air separator uses **centrifugal force** to remove air from circulating boiler water?

Answer 151

Vortex centrifugal style air separator ## Footnote This type is typically used in larger commercial installations.

Question 152

In the context of hot water heating systems, what is the **function of an expansion tank**?

Answer 152

To accommodate air bubbles and maintain an air cushion ## Footnote The expansion tank is directly connected to the air separator.

Question 153

What is the role of the **drain valve** in a hot water heating system?

Answer 153

To allow for the removal of water or air from the system ## Footnote It is an essential component for maintenance.

Question 154

What is the purpose of **flow control valves** in a multi-zone pump system?(2)

Answer 154

* Prevent continued circulation * Stop gravity flow when the circulator is off ## Footnote Flow control valves are necessary to manage water flow and prevent overheating in the system.

Question 155

What is **hydraulic imbalance** in multi-zone systems?

Answer 155

Unequal flow of hot water through each zone ## Footnote This occurs due to differences in piping length and number of heating units connected.

Question 156

What type of valves are commonly used as **balancing valves**?(3)

Answer 156

* Plug valves * Lobe valves with a plug type disc * Lockshield design valves ## Footnote Balancing valves help regulate water flows to ensure each circuit receives the proper amount of water.

Question 157

What should be installed at the beginning of each supply riser and the end of each return riser?

Answer 157

A **gate or ball valve** ## Footnote This allows for servicing without interrupting the operation of the heating system.

Question 158

What is the function of a **pressure reducing valve** in a hot water heating system?

Answer 158

Keeps the system automatically filled and under proper pressure ## Footnote Also known as an automatic fill valve.

Question 159

What type of pumps are used for forced circulation in hot water heating systems?(2)

Answer 159

* Electrically driven centrifugal pumps * Single-stage design pumps ## Footnote These pumps must operate quietly and reliably for long periods.

Question 160

What is the purpose of an **expansion tank** in hydronic systems?(3)

Answer 160

* Accommodate water expansion when heated * Maintain system pressure during cooling * Minimize makeup water and treatment chemicals ## Footnote Expansion tanks prevent excessive pressure buildup in closed hot water heating systems.

Question 161

What happens to water pressure in a hot water heating system when water expands without an expansion tank?

Answer 161

Pressure increases rapidly to the relief valve setting ## Footnote Water is non-compressible, leading to increased pressure if expansion is not accommodated.

Question 162

What type of expansion tanks were used in older residential hot water heating systems?

Answer 162

Open expansion tanks ## Footnote These tanks were installed above the highest radiation element and provided static head pressure.

Question 163

Where are **open type expansion tanks** typically installed?

Answer 163

High up, close to the ceiling ## Footnote This positioning allows air to rise and be collected in the tank.

Question 164

What does the **gauge glass** on a closed expansion tank indicate?

Answer 164

The level of water and air in the tank ## Footnote The water level typically ranges from 1/2 to 2/3 full.

Question 165

What happens when the **water level** in a closed expansion tank rises?

Answer 165

It compresses the air cushion ## Footnote The air acts as a cushion to absorb excess water expansion.

Question 166

What can happen if the air is completely absorbed by the water in an expansion tank?

Answer 166

There will be no air cushion, leading to increased system pressure ## Footnote This can cause the relief valve to open.

Question 167

What is the procedure for **air replacement** in an expansion tank?(4)

Answer 167

* Close the tank inlet valve * Open the tank drain valve * Close the drain valve when air occupies the upper half of the gauge glass * Open the tank inlet valve ## Footnote This procedure helps maintain the air cushion in the tank.

Question 168

What is a **diaphragm closed expansion tank** designed to do?

Answer 168

Separate system water from the compressed air cushion ## Footnote This design helps maintain a permanent air cushion.

Question 169

Where can **diaphragm closed expansion tanks** be installed?

Answer 169

Anywhere in the mechanical room ## Footnote They are commonly used in residential and commercial buildings.

Question 170

What does the **rubber diaphragm** in a diaphragm tank do?

Answer 170

Deflects into the air cushion to compress the air ## Footnote This occurs without a significant pressure increase in the system.

Question 171

What is the purpose of a **diaphragm type expansion tank**?

Answer 171

To accommodate the expansion of water in a closed system ## Footnote It prevents pressure rise and potential discharge from the pressure relief valve.

Question 172

What should you do first when **changing a gauge glass** on an expansion tank?

Answer 172

Use personal protective equipment, face shield, and gloves ## Footnote Safety precautions are essential when handling glass and pressurized systems.

Question 173

List the steps for **removing the broken gauge glass**.(6)

Answer 173

* Shut off the bottom and top isolation valves * Remove the gauge glass guard * Unscrew the nuts holding the glass * Clean out the stuffing box * Check new glass for scratches and nicks * Install new glass with nuts and washers ## Footnote Proper handling and installation are crucial to prevent leaks.

Question 174

What is the typical pressure setting range for a **pressure reducing valve**?

Answer 174

103 kPa to 125 kPa (15 to 18 psi) ## Footnote Taller buildings may require higher pressure settings.

Question 175

What is the purpose of a **backflow prevention device**?

Answer 175

To protect building occupants from contamination of boiler water ## Footnote It is installed on the potable cold water feed line to the boiler.

Question 176

What components are commonly installed with **circulating pumps**?(5)

Answer 176

* Isolation valves * Bypass valves * Check valves * Strainers * Gauges ## Footnote These components ensure proper operation and maintenance of the pump.

Question 177

What is the purpose of **flexible piping connections** on a pump?

Answer 177

To prevent excessive noise and vibration from being transmitted to the building ## Footnote This enhances comfort and reduces wear on the system.

Question 178

What is a **steam to hot water converter** used for?

Answer 178

To heat water for a hot water heating system ## Footnote It is preferable under certain circumstances, such as in multi-storey buildings.

Question 179

In what type of buildings is a **steam-hot water converter system** commonly used?(2)

Answer 179

* Multi-storey buildings * Buildings requiring steam for kitchen, laundry, sterilizers, humidifiers, etc. ## Footnote Hot water is preferred for building heating in these applications.

Question 180

What is the role of the **control valve (A)** in the steam-hot water converter system?

Answer 180

Regulates the steam fed to the converter based on the temperature of the hot water leaving ## Footnote This ensures efficient heating of the water.

Question 181

What happens to steam as it gives heat to the water in the converter?

Answer 181

It condenses and passes through the **steam trap (K)** ## Footnote The condensate is then returned to the boiler via the condensate return system.

Question 182

List the components required in a **hot water heating system** excluding the converter.(3)

Answer 182

* Expansion tank * Relief valve * Fill valve ## Footnote These components are essential for the proper functioning of the system.

Question 183

In a multi-storey building, where is the **steam boiler** typically placed?

Answer 183

In the basement ## Footnote This allows steam to be supplied to converters located at various floor intervals.

Question 184

What is the **importance** of the location of the **circulating pump** and **expansion tank** in a hot water system?

Answer 184

It affects proper operation and can lead to cavitation and negative pressure issues ## Footnote Improper location can cause air to be drawn in and problems in the circulator.

Question 185

What is the **point of no pressure change** in a hot water system?

Answer 185

The point where the pressure in the expansion tank is the same as in the system ## Footnote This point is crucial for maintaining boiler pressure unaffected by the circulating pump.

Question 186

What happens to the **air volume** in the expansion tank when the pressure increases?

Answer 186

It compresses, reducing its volume ## Footnote This compression prevents water from entering the tank since the system is already filled.

Question 187

To determine the **minimum reading** on the altitude gauge of a boiler in a large hot water system, what should be added to the distance from the top of the boiler to the highest point?

Answer 187

1.2 m (4 ft) ## Footnote This ensures adequate pressure is maintained throughout the system.

Question 188

What can occur if the temperature of the water exceeds **57°C (135°F)** in the system?

Answer 188

Vapor bubbles may form ## Footnote This can lead to cavitation and other operating problems.

Question 189

What are some **foreign materials** that can be found in new hot water systems?(7)

Answer 189

* Pipe dope * Thread cutting oils * Soldering flux * Rust preventives * Core sands * Welding slag * Dirt, sand, or clays ## Footnote These materials can inadvertently enter the system during construction and may cause issues.

Question 190

What is the **pH** level that can lead to **corrosion** in hot water systems?

Answer 190

Below 7 ## Footnote A pH below 7 can cause the water to become acidic, leading to corrosion.

Question 191

What should be done to prevent **welding slag** from causing problems in hot water systems?

Answer 191

Install a temporary strainer in the suction line ## Footnote This prevents larger particles from reaching the circulating pump.

Question 192

What is the **preferred method** for cleaning new hot water systems?

Answer 192

Circulate an alkaline solution ## Footnote An alkaline solution can effectively remove impurities that may cause corrosion.

Question 193

List the **chemicals** used for cleaning hot water systems in order of preference.(3)

Answer 193

* Trisodium phosphate * Sodium carbonate (soda ash) * Sodium hydroxide (caustic soda) ## Footnote These chemicals are readily available at hardware stores.

Question 194

What is the first step in the **filling and starting** procedure for a hot water system?

Answer 194

Open all vents and close all drains ## Footnote This step is crucial to vent all air from the system.

Question 195

What should be checked after filling and venting the hot water system?

Answer 195

Check the altitude gauge on the boiler ## Footnote Readjust the automatic fill valve if necessary to obtain the proper pressure.

Question 196

What must be done before using antifreeze in an old hot water system?

Answer 196

Flush out and clean the system ## Footnote This is done by circulating a solution of trisodium phosphate for 3 or 4 hours.

Question 197

What type of **glycol solution** should be used in hot water systems?

Answer 197

Food grade glycol solution (e.g., propylene glycol) ## Footnote This type of solution is safer and suitable for heating systems.

Question 198

What is the first point to observe for the **routine operation** of hot water boilers?

Answer 198

Follow the manufacturer's instructions for routine operation of the boiler ## Footnote This ensures the boiler operates safely and efficiently.

Question 199

What should be done to ensure the **burner operation** is effective?

Answer 199

Observe the operation of the burner regularly and ensure the air supply to the boiler room is open ## Footnote Proper air supply is crucial for efficient combustion.

Question 200

What is a key maintenance task for the **boiler and boiler room**?

Answer 200

Keep the boiler and boiler room clean ## Footnote Covers on all controls should be kept on as they are sensitive to dust and dirt.

Question 201

What should be checked regularly regarding the **circulating pump**?

Answer 201

Check the operation of the pump regularly ## Footnote Ensure it does not drip excessively if equipped with a stuffing box.

Question 202

What type of lubrication do the new style of **residential and commercial circulating pumps** use?

Answer 202

They have a wet rotor which is sealed inside the pump casing ## Footnote These pumps are very efficient and extremely quiet.

Question 203

What should be done if the **expansion tank** becomes waterlogged?

Answer 203

Check for leaks on the tank and gauge glass connections, then recharge it with air ## Footnote Maintaining the air cushion is essential for proper system operation.

Question 204

What is advisable to do with **valves** periodically?

Answer 204

Open and close valves periodically to check their operation ## Footnote Keeping them clean and free from blockage is also important.

Question 205

What type of **air circulation** is produced in a forced warm air heating system?

Answer 205

Positive circulation ## Footnote This allows for a more uniform temperature distribution.

Question 206

List three **advantages** of forced warm air heating systems over gravity warm air systems.(3)

Answer 206

* More uniform temperature distribution * Smaller ducts that can be enclosed within walls and ceilings * Furnace can be located anywhere in the building ## Footnote These advantages enhance the efficiency and flexibility of the heating system.

Question 207

What are two **disadvantages** of forced warm air heating systems?

Answer 207

* Larger air ducts that are difficult to enclose * Potential for noise if not properly designed ## Footnote Noise can be caused by air flow, fan, motor, and combustion equipment sounds.

Question 208

In a forced warm air heating system, how does the **air flow** process begin?

Answer 208

Cooler air is drawn out of rooms through baseboard return grilles ## Footnote This air then flows into the return risers and ducts.

Question 209

What is the role of the **blower** in a forced warm air heating system?

Answer 209

To force air through a heat exchanger ## Footnote This process warms the air before it enters the supply duct.

Question 210

In larger buildings, what type of heating system is often the **primary** heat source?

Answer 210

Steam or hot water heating system ## Footnote A secondary warm air heating system is used for additional heat and ventilation.

Question 211

Fill in the blank: A **fresh air supply duct** allows a controlled amount of outside air to enter the system for _______.

Answer 211

ventilation ## Footnote This air mixes with return air before passing through filters.

Question 212

What are the **common sources of warm air heat**?(3)

Answer 212

* Directly fired * Electric resistance coil * Fin-coil heat exchanger ## Footnote These sources are used in warm air heating systems to provide heat.

Question 213

What are the classifications of **forced warm air furnaces**?(4)

Answer 213

* Direction of air flow (horizontal, upflow, downflow) * Height (lowboy, highboy) * Type of fuel burned (gas, oil-fired) * Heating capacities (kilojoules per hour) ## Footnote These classifications help in selecting the appropriate furnace for installation.

Question 214

What is a **lowboy furnace** used for?

Answer 214

Used where headroom is limited ## Footnote It is about 1.2 m (4 ft) high and suitable for installation in basements.

Question 215

In a **lowboy furnace**, where is the blower located?

Answer 215

Beside the heat exchange section of the furnace ## Footnote This design allows for efficient air circulation and heating.

Question 216

What is the **location** of the blower in a **horizontal furnace**?

Answer 216

Behind the heat exchanger ## Footnote The air enters one end, passes through the filter and blower, over the heat exchanger, and exits at the opposite end.

Question 217

What is the typical height of a **horizontal furnace**?

Answer 217

About 0.6 m ## Footnote These units are used for locations with limited headroom, such as attics and crawl spaces.

Question 218

In a **highboy or upflow furnace**, where is the blower located?

Answer 218

Beneath the heat exchanger ## Footnote This type of furnace discharges air vertically upward and saves floor space.

Question 219

How does air enter a **highboy or upflow furnace**?

Answer 219

Through the bottom or side via the filter ## Footnote Air leaves the furnace at the top.

Question 220

What is a common installation location for a **highboy or upflow furnace** in buildings without basements?

Answer 220

First floor or in a closet ## Footnote A return duct is often not required in such installations.

Question 221

In a **downflow furnace**, where is the blower located?

Answer 221

Above the heat exchanger ## Footnote The air enters from the top and is discharged at the bottom.

Question 222

What type of buildings typically use a **downflow furnace**?

Answer 222

Buildings without basements ## Footnote Warm air supply ducts are set in the concrete floor slab or in a crawl space beneath the floor.

Question 223

What is a common application for a **unit heater**?

Answer 223

Shops and warehouses ## Footnote It can have its own blower or fan.

Question 224

What is the advantage of using **duct furnaces** in larger buildings heated solely by a warm air system?

Answer 224

Can easily accommodate varying heat demand of different zones ## Footnote This system allows for multiple duct furnaces instead of one centrally located warm air furnace.

Question 225

What does a **rooftop heating unit** consist of?(4)

Answer 225

* Horizontal air heater * Weatherproof casing * Supply duct * Cool air return duct ## Footnote It is mounted on the roof and protects against the elements.

Question 226

How does the **electric warm air furnace** heat the cool return air?

Answer 226

By passing it over a set of open wire resistance heating elements ## Footnote This furnace is compact compared to directly fired furnaces.

Question 227

What regulates and mixes the outdoor and return air flows in a rooftop heating unit?

Answer 227

A set of dampers ## Footnote These dampers are essential for maintaining air quality and temperature.

Question 228

Fill in the blank: The **voltage supplied** to the heating elements in an electric warm air furnace varies depending on _______.

Answer 228

availability ## Footnote This ensures that the furnace operates efficiently based on the power supply.

Question 229

What protects the heating elements in an electric warm air furnace against overheating?

Answer 229

A high-temperature limit control and airflow sensing switch ## Footnote These safety features prevent damage to the furnace.

Question 230

What is a key benefit of using **electric furnaces** compared to directly fired furnaces?(3)

Answer 230

* Higher efficiency * Lower maintenance cost * Flexibility in location ## Footnote These benefits contribute to overall cost-effectiveness.

Question 231

What type of heaters are used for the same purposes as directly fired duct furnaces?

Answer 231

Electric duct heaters ## Footnote They serve similar functions in heating air within duct systems.

Question 232

What type of **heat exchanger** is often used to heat ventilating air?

Answer 232

fin-coil type ## Footnote It is often more advantageous to heat the ventilating air by means of a steam or hot water heater.

Question 233

What is the **basic diagram** of a building heating system composed of?(2)

Answer 233

* Primary hydronic heat * Secondary heat supplied by a hot water heat exchanger ## Footnote This system includes a supply duct for distributing heated air.

Question 234

What are the **operational characteristics** of directly fired space heaters?(2)

Answer 234

* Heats air directly without ducting * Installed in the space to be heated ## Footnote Space heaters are preferred in areas where duct systems are impractical.

Question 235

Name some commonly used **space heaters**.(3)

Answer 235

* Unit heater * Floor furnace * Wall furnace ## Footnote These heaters vary in design but operate on similar principles.

Question 236

What is a **unit heater** similar to in construction?

Answer 236

duct furnace ## Footnote The heat exchanger and burner equipment are mounted in a cabinet suspended from the ceiling.

Question 237

What distinguishes **large unit heaters** from low-capacity ones?(2)

Answer 237

* Equipped with filters * Air is moved by one or more centrifugal fans ## Footnote These features enhance their efficiency in larger spaces.

Question 238

Describe the operation of a **floor furnace**.(3)

Answer 238

* Similar to an upflow furnace * Air is drawn into the blower compartment from the space * Heated air is discharged through discharge cowls ## Footnote This design allows for direct heating of the space.

Question 239

What is a **wall furnace** designed to do?

Answer 239

Recess into the wall ## Footnote This design saves floor space while providing heating.

Question 240

What is the **annual fuel utilization efficiency (AFUE)** range for traditional warm air furnaces?

Answer 240

70% to 75% ## Footnote This indicates that only 70% to 75% of the heat from the fuel burned is transferred to the air.

Question 241

What is the maximum **AFUE** range for improved furnaces currently marketed?

Answer 241

80% to 98% ## Footnote These improvements are due to advancements in furnace technology.

Question 242

What device minimizes heat loss up the stack when burners are off in a furnace?

Answer 242

Vent damper ## Footnote It traps residual heat in the heat exchanger when the burners are shut off.

Question 243

What is the purpose of a **secondary heat exchanger** in high-efficiency furnaces?

Answer 243

Increases heat recovery ## Footnote It allows for additional heat transfer to the air, raising efficiency.

Question 244

What happens to flue gases in a secondary heat exchanger?

Answer 244

Temperature drops to about 65°C (149°F) ## Footnote This results in an efficiency increase to 85% to 87% AFUE.

Question 245

What can form when sulphur in fuel combines with condensate in a secondary heat exchanger?

Answer 245

Sulphuric acid ## Footnote This can corrode the exchanger, blower, and venting.

Question 246

What is the efficiency range of a **pulse combustion condensing furnace**?

Answer 246

94% to 98% AFUE ## Footnote This type of furnace has an elongated combustion chamber with external fins.

Question 247

Describe the initial step in the **combustion process** of a pulse combustion furnace.

Answer 247

The furnace is purged by the air intake blower ## Footnote After purging, the gas valve opens to allow gas flow into the combustion chamber.

Question 248

What role does the **spark plug** play in a pulse combustion furnace?

Answer 248

Acts as an igniter for initial combustion ## Footnote It starts the combustion process in the chamber.

Question 249

What happens to the pressure in the combustion chamber after the gas-air mixture ignites?

Answer 249

Positive pressure buildup occurs ## Footnote This forces combustion products upwards through the chamber.

Question 250

What is the function of the **induced draft blower** in a high-efficiency furnace?

Answer 250

Controls the flow of combustion air and fuel ## Footnote It ensures proper sequence for ignition and operation.

Question 251

What is the temperature at which flue gases exit conventional furnaces?

Answer 251

About 230°C (450°F) ## Footnote This is significantly higher than the exit temperature of high-efficiency furnaces.

Question 252

Fill in the blank: The **heat exchanger** in a high-efficiency furnace is designed with _______ flue gas channels.

Answer 252

S-shaped ## Footnote This design increases contact time with the heat exchanger surfaces.

Question 253

What is the shape of the **heat exchange section** in oil-fired furnaces?

Answer 253

Cylindrical ## Footnote It is mounted above the combustion chamber.

Question 254

In gas-fired furnaces, heat exchangers consist of a number of flat, hollow channels made of **________**.

Answer 254

Steel plate ## Footnote The hot combustion gases travel upward through the channels to the flue.

Question 255

What type of **burners** are commonly used in warm air furnaces?(2)

Answer 255

* Atmospheric gas burners * High-pressure spray atomizing oil burners ## Footnote These are similar to those used in low-pressure steam and hot water heating boilers.

Question 256

How is the blower rotor often mounted in relation to the **motor shaft**?

Answer 256

Directly on the motor shaft ## Footnote This allows it to run at the same speed as the motor.

Question 257

What is the purpose of the **cutoff plate** in the blower system?

Answer 257

Air discharge control ## Footnote It helps regulate the airflow from the blower.

Question 258

What type of drive can be used for the blower if it is not directly mounted on the motor shaft?

Answer 258

Belt-driven ## Footnote This setup allows for lower speeds than the motor.

Question 259

What is the purpose of **cushion mounts** in a warm air furnace?

Answer 259

To isolate the motor and rotor from the blower housing and furnace, preventing vibration and noise transfer ## Footnote This helps maintain a quieter operation of the heating system.

Question 260

What do **air filters** do in warm air heating systems?

Answer 260

Trap airborne particles of dirt, dust, pollen, and lint ## Footnote Filters are installed on the suction side of the blower, either in the return air duct or in the blower compartment.

Question 261

Where is a **humidifier** typically installed in a warm air heating system?

Answer 261

In the warm air plenum of the furnace or in the supply duct ## Footnote It supplies moisture to maintain the required relative humidity in heated spaces.

Question 262

What is **perimeter heating**?

Answer 262

Warm air outlets located along the outside walls of rooms at or near floor level ## Footnote This design helps to effectively heat spaces, especially below windows.

Question 263

What is the function of **return outlets** in a warm air heating system?

Answer 263

Remove cooler air through grilles placed near the floor in inside walls ## Footnote These outlets connect with the return duct to direct air back to the furnace.

Question 264

Describe the **Perimeter Loop System**.

Answer 264

A continuous, closed loop supply duct around the perimeter of the building ## Footnote Ideal for buildings with a concrete slab floor and no basement, preventing cold floor conditions.

Question 265

What is the **Perimeter Radial System** used for?

Answer 265

Delivering supply air from a central plenum to each outlet by separate ducts ## Footnote Mainly used in buildings with crawl space or slab floor construction.

Question 266

In a building with a basement, what must be considered when using a **Perimeter Radial System**?

Answer 266

Additional basement height is required ## Footnote Some supply ducts must be located below the joist level.

Question 267

What is the most commonly used duct system for warm air heating systems?

Answer 267

Extended plenum system ## Footnote Used in both small and large buildings.

Question 268

Describe the structure of the **Extended Plenum System**.

Answer 268

Rectangular supply plenum with extended plenums branching off ## Footnote Usually located along the center line of the building.

Question 269

What materials are air ducts available in?(2)

Answer 269

* Galvanized sheet metal * Fiberglass ## Footnote Various cross-section shapes are used, such as circular and rectangular.

Question 270

What is a key advantage of **circular ducts**?

Answer 270

Use less material and offer less resistance to airflow ## Footnote However, rectangular ducts are often preferred for ease of installation.

Question 271

What is the purpose of **dampers** in branch ducts?

Answer 271

To adjust warm airflow to various areas ## Footnote Ensures equal comfort throughout the building.

Question 272

What is a **Register** in HVAC systems?

Answer 272

A grill equipped with a damper to control the amount of air passing through ## Footnote It regulates the air entering the room to be changed.

Question 273

Define **Fixed louvre register**.

Answer 273

A register with fixed bars or louvres that direct the air in a specific pattern ## Footnote Used to control airflow direction.

Question 274

What is a **Grille**?

Answer 274

A covering for any opening through which air passes ## Footnote Essential for air distribution in HVAC systems.

Question 275

What is an **Adjustable louvre register**?

Answer 275

A register with movable bars or louvres that allow the flow pattern to be changed ## Footnote Provides flexibility in directing airflow.

Question 276

What does a **Ceiling diffuser** do?

Answer 276

Spreads air without causing drafts ## Footnote Typically square or circular shaped, covering the ceiling outlet.

Question 277

What are **Perforated panels** used for?

Answer 277

Installed in the ceiling or upper walls to provide air over a large area ## Footnote Effective for distributing warm air.

Question 278

Where should **supply outlets** be located?

Answer 278

To prevent cold drafts from walls and windows ## Footnote Baseboard and floor registers, as well as window slots, are commonly used.

Question 279

What types of registers are often used for heating and ventilation?(3)

Answer 279

* Ceiling diffusers * Perforated ceiling panels * Sidewall registers ## Footnote These are used when warm air is the only source of heat supply.

Question 280

What is the purpose of **aspiration** in HVAC systems?

Answer 280

To draw cooler room air into the airstreams ## Footnote It helps mix cold air with warm air for better temperature distribution.

Question 281

What are the **recommended maintenance procedures** for warm air heating and ventilating systems?(4)

Answer 281

* Check fans and blowers at prescribed intervals * Clean dust from blades or vanes at least once a year * Lubricate electric motor bearings as needed * Vacuum or blow clear air openings to the motor ## Footnote Proper maintenance ensures satisfactory and dependable service.

Question 282

What should be done if **unusual sounds** are heard from the fan or blower?

Answer 282

Investigate immediately ## Footnote Any obstruction to the free rotation of the blades may destroy the unit.

Question 283

What type of **bearings** do smaller capacity blowers and motors usually have?(2)

Answer 283

* Sealed ball bearings * Sleeve bearings ## Footnote Sealed ball bearings require no lubrication, while sleeve bearings need oil twice a year.

Question 284

What is the consequence of **over-lubricating** motor bearings?

Answer 284

Excess oil may attack insulation and cause short-circuiting ## Footnote An oil-soaked surface also causes dust to accumulate.

Question 285

What is the purpose of the **V-belt** in a warm air furnace?

Answer 285

To drive the blower at a lower speed than the motor ## Footnote The speed is reduced by using pulleys of different sizes.

Question 286

How can the **blower speed** be varied in a warm air furnace?

Answer 286

By adjusting the movable flange of the adjustable pulley ## Footnote This changes the volume of air moved through the heating system.

Question 287

What is crucial for the **alignment of pulleys** in a warm air furnace?

Answer 287

Pulleys should be in a straight line and shafts should be parallel ## Footnote Misalignment can cause the V-belt to fray and wear quickly.

Question 288

What is the recommended maintenance for **controls** in warm air furnaces?

Answer 288

No maintenance required, but operation should be checked during servicing ## Footnote Room thermostats may require gentle blowing to remove dust deposits.

Question 289

Why should **ducts** be kept as airtight as possible?

Answer 289

* Prevent insufficient warm air supply * Avoid heat wastage ## Footnote Leaks at section joints are often neglected but can significantly impact performance.

Question 290

How often should **filters** be cleaned in warm air furnaces?

Answer 290

At least four times a year ## Footnote More frequent cleaning is necessary if dust conditions are high.

Question 291

What maintenance is required for **gas burners** in warm air furnaces?

Answer 291

Generally require no maintenance ## Footnote Keep the pilot light free from dust accumulation.

Question 292

What can happen if a **heat exchanger** fails?

Answer 292

Carbon monoxide could enter the warm air stream ## Footnote This poses a danger to building occupants.

Question 293

What is the consequence of not cleaning **filters** regularly?(4)

Answer 293

* Loading or clogging of filters * Limited airflow * Insufficient heating * Waste of fuel ## Footnote Regular maintenance is crucial for efficient operation.

Question 294

What should be done if **belts** are unmatched in a blower or fan system?

Answer 294

Replace belts as a matched set ## Footnote Unmatched belts can lead to uneven wear and early failure.

Question 295

What are the two basic methods of **ventilation**?

Answer 295

* Natural * Mechanical ## Footnote Natural ventilation relies on temperature differences or wind, while mechanical ventilation uses motor-driven fans or blowers.

Question 296

In **natural ventilation**, how is air movement primarily achieved?

Answer 296

By opening windows ## Footnote This method is often inefficient and can create cold drafts.

Question 297

What do new building codes require for proper home **ventilation**?

Answer 297

A main or principal exhaust fan ## Footnote This ensures adequate ventilation in the home.

Question 298

What happens when the **exhaust fan** is turned on in a residential ventilation system?

Answer 298

The furnace blower is started, allowing ventilation air to enter the fresh air duct ## Footnote This occurs at the rate that air is leaving the system.

Question 299

What are the **three groups** of mechanical ventilation systems?

Answer 299

* Natural air intake, mechanical exhaust * Mechanical air intake, natural exhaust * Mechanical air intake, mechanical exhaust ## Footnote These groups categorize ventilation systems based on how air is moved in and out of buildings.

Question 300

What is a disadvantage of the **Natural Air Intake, Mechanical Exhaust** system?(3)

Answer 300

* Fresh air is neither filtered nor heated * Risk of back-venting gas-fired appliances * Creates slightly lower pressure in the building ## Footnote These disadvantages can lead to safety and comfort issues.

Question 301

What are the methods for supplying fresh air in the **Mechanical Air Intake, Natural Exhaust** system?(4)

Answer 301

* Propeller fan mounted in the outside wall * Fresh air supply duct in a warm air heating system * Unit ventilators * Makeup air heater ## Footnote These methods ensure fresh air is introduced into the building.

Question 302

What is the advantage of a **fully mechanical ventilation system**?

Answer 302

Supplies controlled amount of filtered and heated air ## Footnote Proper design avoids discomfort for occupants and ensures effective air distribution.

Question 303

What is the role of the **exhaust fan** in the Natural Air Intake, Mechanical Exhaust system?

Answer 303

Draws stale air out of the rooms ## Footnote It creates a pressure difference that affects air flow into the building.

Question 304

Fill in the blank: The **exhaust duct system** is advantageous due to its simple design, low cost, and ease of maintenance, but it is not very _______.

Answer 304

energy efficient ## Footnote The continuous operation of one fan can lead to unnecessary exhaust.

Question 305

How is the size of air contaminants measured?

Answer 305

In microns ## Footnote 1 micron is one-thousandth of a millimeter, and sizes vary from 0.2 microns (tobacco smoke) to over 1000 microns (dust particles).

Question 306

Why is it impossible to design a **single air cleaner** for all contaminants?

Answer 306

Due to the variety in sizes of contaminants ## Footnote Different types of air cleaners are needed to address specific contaminants and their concentrations.

Question 307

The type of air cleaner used in an air conditioning system depends on what factors?(3)

Answer 307

* Type of contaminants * Concentration of contaminants * Degree of cleanliness desired ## Footnote These factors determine the effectiveness of air cleaning systems.

Question 308

What are the **classifications** of air cleaning devices used in buildings?(6)

Answer 308

* Air filters for the removal of solid and liquid particles * Electronic air cleaners * Air washers * Charcoal absorbers for the removal of gases and vapours * Activated alumina chemisorbant media for the removal of corrosive gases such as H₂S, SO₂, Cl₂ * Devices such as ultraviolet or germicidal lamps for the removal of bacteria ## Footnote These classifications help in understanding the various methods of air purification in buildings.

Question 309

Mechanical air filters for industrial applications can be divided into **two broad classes**. Name them.

Answer 309

* Throwaway filters * Cleanable or renewable filters ## Footnote These classes indicate the disposability and reusability of the filters.

Question 310

What is the primary characteristic of **throwaway filters**?

Answer 310

Use a filtering medium cheap enough to be disposed of when it becomes dust laden ## Footnote This type of filter is designed for single-use applications.

Question 311

What are the two types of **cleanable or renewable filters**?

Answer 311

* Dry filters * Viscous filters ## Footnote These filters can be cleaned and reused, making them more sustainable.

Question 312

What is the maximum air movement speed for **dry filters**?

Answer 312

0.25 m/s (50 feet per minute) ## Footnote This speed ensures effective filtration without overwhelming the filter.

Question 313

What materials are commonly used in the majority of **dry filters**?(2)

Answer 313

* Fibreglass * Cellulose ## Footnote These materials are often used due to their cost-effectiveness.

Question 314

What is a **roller or curtain filter**?

Answer 314

A filter consisting of a frame placed across the air duct with two rolls of filter mat ## Footnote This design allows for continuous filtration as the filter mat is replaced automatically.

Question 315

How is the operation of a **rotating air filter** controlled?(2)

Answer 315

* Adjustable time clock * Pressurestat actuated by the static pressure drop across the filter ## Footnote These controls ensure the filter is replaced or cleaned at appropriate intervals.

Question 316

What happens when the entire clean roll of a **rotating air filter** is used up?

Answer 316

A new roll is installed, and the dirty roll is either cleaned or disposed of ## Footnote This process maintains continuous air filtration in larger systems.

Question 317

What are the two types of **replaceable filters** mentioned?

Answer 317

* Bag type * Multiwedge type ## Footnote Both types are made from a special modacrylic fibre and have a large filtering area and dirt holding capacity.

Question 318

What is the purpose of a **pad type pre-filter**?

Answer 318

To protect the more expensive bag or multiwedge filter ## Footnote Failure to provide pre-filtering will result in more frequent changes of expensive filters.

Question 319

What are **Viscous Impingement Filters** commonly used for?

Answer 319

Ordinary air conditioning systems ## Footnote They contain tightly packed filter media coated with a viscous or sticky fluid.

Question 320

What materials can be found in **Viscous Impingement Filters**?(4)( What they are made of)

Answer 320

* Glass fibre * Copper wool * Aluminum wool * Crimped metal ## Footnote These materials help in adhering dust particles as air passes through the filter.

Question 321

What is a common air velocity through a **viscous filter**?

Answer 321

2.5 metres per second (500 ft per minute) ## Footnote This velocity can be much higher than through a dry filter.

Question 322

How is a **cleanable viscous filter** maintained?

Answer 322

Washed in cleaning solution, dried, and coated with viscous oil ## Footnote Excess oil is drained off before storage for future use.

Question 323

What is the construction of a **permanent, washable, viscous panel filter**?

Answer 323

Layers of crimped and expanded aluminum foil in a zinc-coated holding frame ## Footnote This design allows for effective filtration and durability.

Question 324

What is the orientation of the **roll-type viscous filter**?

Answer 324

* Mounted vertically with horizontal media movement * Mounted horizontally with vertical media movement ## Footnote This design allows for flexibility in installation and operation.

Question 325

What are the **two classes** of electronic air cleaners?

Answer 325

* Electrostatic precipitators * Charged-media electronic air cleaners ## Footnote These classes categorize electronic air cleaners based on their operational principles.

Question 326

Describe the **function** of **electrostatic precipitators**.

Answer 326

They charge dust particles and collect them on metal plates using high voltage. ## Footnote The airflow passes through an ionizing zone, and contaminants are removed by washing the collector plates.

Question 327

What is the **voltage** range used in the ionizing wires of electrostatic precipitators?

Answer 327

12,000 to 13,000 V DC ## Footnote This high voltage is essential for charging the dust particles in the airflow.

Question 328

What is the **advantage** of using **charged-media electronic air cleaners** over electrostatic precipitators?

Answer 328

They continue to act as impingement filters even if the power supply fails. ## Footnote This ensures some level of air cleaning is maintained during power outages.

Question 329

What is a major **disadvantage** of charged-media electronic air cleaners?

Answer 329

They offer resistance to airflow, which increases as the filter becomes loaded with contaminants. ## Footnote This can affect the efficiency of the air cleaning process.

Question 330

What does **HEPA** stand for?

Answer 330

High Efficiency Particulate Air filters ## Footnote HEPA filters can filter down to 0.3 microns at 99% efficiency and are commonly used in hospitals.

Question 331

What is the primary **function** of **air washers**?(4)

Answer 331

They can be used for air cleaning, humidification, dehumidification, or cooling. ## Footnote However, their efficiency in dust removal is low.

Question 332

What type of **filter** is commonly used before air washers?

Answer 332

Pre-filters ## Footnote These filters remove impurities in the air before it passes through the air washers.

Question 333

What is the most common method for removing **odours** in an air conditioning system?

Answer 333

Activated carbon placed in cylindrical canisters ## Footnote Activated carbon can adsorb odour-causing gases up to about 20% of its own weight before needing replacement.

Question 334

At what temperature can activated carbon be **reactivated**?

Answer 334

538°C (1000°F) ## Footnote Heating drives out the adsorbed gases from the activated carbon.

Question 335

Why is the control of **airborne bacteria and mould spores** important in certain buildings?

Answer 335

* Hospitals * Nurseries * Food processing and storage plants * Pharmaceutical and cosmetic plants ## Footnote Improper control may cause the spreading of diseases and spoilage of food.

Question 336

What type of lamps are used to **sterilize air** in buildings?

Answer 336

Germicidal lamps ## Footnote These lamps emit ultraviolet light that effectively destroys bacteria and spores.

Question 337

In **in-duct air sterilizers**, what is the purpose of the ultraviolet lamps?

Answer 337

To destroy bacteria before the air enters conditioned spaces ## Footnote The sterilizer consists of circular channels containing tubular ultraviolet lamps.

Question 338

What is **activated alumina chemisorbant** used for?(2)

Answer 338

* Removing odours * Removing irritant contaminants ## Footnote It absorbs contaminants and chemically destroys them using an oxidizing agent.

Question 339

What is the diameter of activated alumina pellets used in chemisorbants?

Answer 339

3 to 6 mm ## Footnote The pellets are impregnated with an oxidizing agent like potassium permanganate.

Question 340

What is the function of **pre-filters** in activated alumina systems?

Answer 340

To prevent atmospheric dust from clogging the pores of the chemisorbant pellets ## Footnote Pre-filters have an efficiency of 30% to 35%.

Question 341

What is a significant application of activated alumina chemisorbant in industrial settings?

Answer 341

Preventing premature failure of electronic equipment ## Footnote Particularly important in environments like pulp and paper, petrochemical, and fertilizer plants.

Question 342

What pressure drop range is typical for activated alumina chemisorbant systems?

Answer 342

0.25 to 0.65 kPa ## Footnote This pressure drop can cause problems in balancing the air conditioning system.

Question 343

How do **infrared heaters** work?

Answer 343

They send out radiant energy in the form of invisible infrared waves that travel through the air without warming it ## Footnote When these waves strike a solid, opaque object, the radiant energy is converted into heat.

Question 344

Where are **infrared heaters** typically mounted for comfort heating?

Answer 344

Overhead, directing radiant energy downward to the floor and to persons or objects on the floor ## Footnote This setup allows for comfort even when surrounding air temperature is low.

Question 345

What is the purpose of **area heating** in infrared heating?

Answer 345

To heat only the lower part of a large interior space, leaving the remainder unheated ## Footnote This is particularly useful in large buildings with high bay structures.

Question 346

What are the advantages of using **infrared heating** in large buildings?

Answer 346

* Achieves comfort for occupants * Saves heating costs by leaving upper areas unheated ## Footnote Infrared heating directs energy toward the floor, keeping upper levels cool.

Question 347

Give an example of **radiant area heating**.

Answer 347

Skating arenas and curling rinks ## Footnote These buildings require low air temperatures to protect the ice surface while keeping spectators warm.

Question 348

What is **spot heating**?

Answer 348

Heating that covers only a very small area, used in open work sheds, loading docks, and bus stop shelters ## Footnote Spot heating compensates for increased body heat losses in low air temperatures.

Question 349

What is a common application of **spot heating**?

Answer 349

Snow melting at building entrances and on parkade ramps ## Footnote Spot heating is essential in areas exposed to outside temperatures.

Question 350

What is the primary principle behind **gas-fired infrared heaters**?

Answer 350

A direct flame heats a solid surface, which then emits infrared energy by radiation ## Footnote The radiant heat emitted by a gas flame is only a small portion of the total heat produced.

Question 351

What is the temperature range for the surface of a **Surface Combustion Heater**?

Answer 351

760°C to 900°C (1400°F to 1650°F) ## Footnote This heater employs a porous or drilled ceramic mat to direct energy waves onto a specific area.

Question 352

What type of heater is described as **unvented** and allows combustion gases to escape upward?

Answer 352

Surface Combustion Heater ## Footnote Sufficient ventilation must be provided to remove combustion gases and prevent excessive moisture buildup.

Question 353

What is the temperature range for a **Directly Fired Refractory Heater**?

Answer 353

980°C to 1260°C (1800°F to 2300°F) ## Footnote This heater has a radiating surface consisting of a block of refractory heated by the burner flame.

Question 354

What is the main feature of an **Internally Fired or Vented Heater**?

Answer 354

It consists of a heat exchanger where the gas-air mixture is burned inside ## Footnote Most heat is transmitted to the emitting surface, which reaches temperatures over 400°C (750°F).

Question 355

What is the purpose of the **reflectors** in an Internally Fired or Vented Heater?

Answer 355

To direct the infrared energy radiated by the emitting surface in a specific pattern ## Footnote Reflectors enhance the efficiency of heat distribution.

Question 356

What is the function of the **Low Temperature Catalytic Heater**?

Answer 356

Promotes oxidation of the gas-air mixture to burn fuel slowly without a flame ## Footnote This results in lower emission temperatures of 315°C to 455°C (600°F to 850°F).

Question 357

What materials are used in the construction of a **Low Temperature Catalytic Heater**?(3)

Answer 357

* Glass wool impregnated with a catalyst * Porous refractory * Metal screen ## Footnote The catalyst promotes oxidation, allowing for slow combustion without a flame.

Question 358

What are the **three most commonly used types** of electric infrared heating elements?(3)

Answer 358

* Metal Sheath Element * Quartz Tube Heater * Quartz Lamp ## Footnote Each type has distinct characteristics and applications.

Question 359

Describe the **Metal Sheath Element**.(5)

Answer 359

* Consists of a nickel-chrome spiral resistor * Embedded in insulating refractory * Surrounded by a metal tube or sheath * Diameter: 9.5 mm (3/8 in) * Length: up to 198 cm (78 in) ## Footnote It is known for its ruggedness and resistance to thermal shock, vibration, and impact.

Question 360

What is the **response time** and maximum temperature of the **Metal Sheath Element**?

Answer 360

* Response Time: 3 minutes * Maximum Temperature: 845°C (1550°F) ## Footnote It has the longest heating time among the three types.

Question 361

What are the characteristics of the **Quartz Tube Heater**?(4)

Answer 361

* Coiled nickel-chrome element * Enclosed in an air-filled quartz tube * Response Time: 1 minute * Maximum Temperature: 815-930°C (1500-1700°F) ## Footnote It has a lower power consumption than the Metal Sheath Element.

Question 362

What is the **maximum temperature** and **luminosity** of the **Quartz Lamp**?

Answer 362

* Maximum Temperature: 2200°C (4000°F) * Luminosity: High, 7.5 lumens per W ## Footnote It has the fastest response time and highest radiation efficiency.

Question 363

What is the **function** of the reflector lamp (heat lamp)?(3)

Answer 363

* Used in industrial applications (e.g., paint drying) * Hair drying in bathrooms * Keeping food warm in restaurants and kitchens ## Footnote It is available in 125, 250, and 375 watt capacities.

Question 364

What is the **construction** of the heat lamp?(4)

Answer 364

* Coiled tungsten heating filament * Slightly flattened heat-resistant glass bulb * Silver-coated inside to reflect infrared waves * Fits any ordinary 120-volt light socket ## Footnote The front part of the bulb can be clear, frosted, or red.

Question 365

Fill in the blank: The **Metal Sheath Element** has excellent thermal shock, vibration, and impact resistance, but loses radiating capacity drastically if exposed to _______.

Answer 365

wind ## Footnote This makes it less suitable for outdoor applications.

Question 366

What are the **advantages** of electric heating systems compared to other types of heating systems?(6)

Answer 366

* Absence of combustion and combustion gases * Requires less space * Individual room temperature control * Lower installation cost * Clean and silent operation * Lower maintenance cost ## Footnote Electric heating devices produce no toxic gases and require no combustion air, chimney, or fuel storage.

Question 367

Electricity can be directly converted into **heat energy** in what type of heating elements?

Answer 367

Electric resistance heating elements ## Footnote Heating elements are made of metals that offer high resistance to the flow of an electric current.

Question 368

Name the **three common types** of electric heating elements.

Answer 368

* Open wire * Open ribbon * Tubular-cased wire ## Footnote Each type has specific designs and applications for safety and efficiency.

Question 369

What type of electric heating equipment is installed in the areas to be heated, providing direct heat?

Answer 369

Direct Heating ## Footnote This method allows heat to be transferred directly from the source to the air and/or objects in the area.

Question 370

What is a **baseboard heater**?

Answer 370

A popular natural convection type heater consisting of one or two tubular elements fitted with aluminum fins ## Footnote Baseboard heaters are easy to install, take minimal space, and are noiseless.

Question 371

What type of heater uses an open wire or ribbon type heating element that operates at infrared temperature?

Answer 371

Radiant Heater ## Footnote The heat is radiated directly into the room from the front of the element.

Question 372

What is the function of a **thermostat** in electric heating systems?

Answer 372

To control the operation of the heating units ## Footnote Thermostats can be mounted on the unit or on the wall for individual room control.

Question 373

What is the primary method of heating in **radiant panel heaters**?

Answer 373

Heating by radiation from warmed sections of the ceiling, walls, or floor ## Footnote Similar to the tubing in a hydronic radiant panel heating system.

Question 374

What type of heating do **heat lamps** provide?

Answer 374

Direct heating for spot applications ## Footnote Infrared heat lamps are commonly used for this purpose.

Question 375

How does an **electric snow melting system** operate?

Answer 375

Uses electric resistance cables or wires embedded in paving materials ## Footnote Similar in application to hydronic snow melting systems.

Question 376

What controls the operation of an electric snow melting system?(3)

Answer 376

* Manual control with a pilot light * Automatic control by a snow detector * Outdoor thermostat to prevent operation during warm weather ## Footnote The thermostat turns off the system when outdoor temperature rises above 2°C (35.5°F).

Question 377

What is **indirect heating**?

Answer 377

Heat supplied by electric energy transferred to a medium that carries the heat ## Footnote This method is used in various heating systems.

Question 378

In what systems can **electric boilers** be used?(2)

Answer 378

* Steam heating systems * Hydronic heating systems ## Footnote Electric boilers supply heat by converting electric energy into heat energy.

Question 379

What type of heating elements are commonly used in **central warm air furnaces**?

Answer 379

Electric resistance heating elements of the open wire type ## Footnote These methods are considered indirect as heat is transferred to the air.

Question 380

What happens to **nose and throat membranes** during cold weather due to dry air?

Answer 380

They dry up, causing discomfort ## Footnote Dry air can also lead to cracked lips and static electric shocks.

Question 381

What is the definition of **humidity**?

Answer 381

Water vapour or moisture in the air ## Footnote The amount of moisture air can hold depends on temperature.

Question 382

How does **temperature** affect the amount of moisture air can absorb?

Answer 382

Higher temperature allows more moisture absorption; lower temperature allows less ## Footnote For example, air at 21°C can hold more moisture than air at -18°C.

Question 383

What is **relative humidity**?

Answer 383

The amount of moisture in the air compared to the maximum it can hold at a given temperature ## Footnote Expressed as a percentage.

Question 384

What happens to the **relative humidity** when air is heated without adding moisture?

Answer 384

It drops ## Footnote For example, heating air from 5°C to 21°C reduces its relative humidity from 100% to 33%.

Question 385

What causes **dryness** in a building during cold weather?

Answer 385

Outside air is drawn in and heated, causing a sharp drop in relative humidity ## Footnote This can lead to discomfort and other issues related to dry air.

Question 386

Why is it necessary to add **humidity** to the air during the heating season?

Answer 386

To maintain comfortable conditions inside a building ## Footnote Adding humidity is important for health and comfort.

Question 387

What happens when **slight condensation** appears in the corners of window panes?

Answer 387

The relative humidity inside the building has reached its maximum ## Footnote This indicates the need to monitor humidity levels.

Question 388

What are the **three types of humidifiers** used for residential purposes?

Answer 388

* Pan Type Humidifier * Wetted Element Humidifier * Atomizing Humidifier ## Footnote Each type has different mechanisms for adding moisture to the air.

Question 389

Describe the **Pan Type Humidifier**.

Answer 389

Consists of a shallow pan with absorbent plates; water evaporates as warm air passes over ## Footnote It has a low humidification rate and uses a float valve to control water level.

Question 390

What is the function of the **Wetted Element Humidifier**?

Answer 390

Uses a water-saturated evaporation pad to humidify air ## Footnote The humidification capacity varies with temperature, humidity level, and air velocity.

Question 391

What are the two types of **Wetted Element Humidifiers**?

Answer 391

* Power Type * Bypass Type ## Footnote Power Type uses a fan, while Bypass Type relies on pressure difference created by the furnace blower.

Question 392

What distinguishes a **Power Type** humidifier from a **Bypass Type** humidifier?

Answer 392

Power Type has a fan; Bypass Type uses pressure difference without a fan ## Footnote Bypass Type is connected to both supply and return plenums.

Question 393

What controls the operation of the **Bypass Type** humidifier?

Answer 393

A humidistat mounted in the living area or on the return duct ## Footnote It ensures operation only when the furnace fan is running.

Question 394

What is the function of an **atomizing humidifier**?

Answer 394

Breaks water into small particles using a spray nozzle or spinning disc ## Footnote The spinning disc type atomizes water into a fine mist, typically used as a room unit.

Question 395

In a **spray humidifier**, how is water distributed?

Answer 395

Water under pressure is forced through a nozzle, creating a fog ## Footnote This fog is absorbed by the air, and a humidistat controls the water supply.

Question 396

What maintenance is required for **humidifiers** to prevent mineral buildup?(4)

Answer 396

* Clean evaporation plates and pads * Soak in slightly acidic solution * Wash in soapy water * Clean tray or pan to remove salt buildup ## Footnote Regular cleaning is essential to keep humidifiers in top condition.

Question 397

What components are primarily found in an **air washer**?(4)

Answer 397

* Casing * Spray chamber * Spray nozzles * Eliminators ## Footnote The air flows through the chamber and is in contact with the spray water.

Question 398

What is the function of **eliminators** in an air washer?

Answer 398

Prevent droplets of water from being carried away by the air ## Footnote They change the direction of airflow, causing droplets to impinge on their surfaces.

Question 399

What types of particles are removed by an **air washer**?(2)

Answer 399

* Dust particles * Some odours ## Footnote Air washers are not effective in removing greasy particles, soot, or tobacco smoke.

Question 400

In an **atomizing humidifier**, what should be checked regularly for proper operation?(2)

Answer 400

* Nozzle * Screen ## Footnote Cleaning the nozzle and screen is necessary to ensure efficient functioning.

Question 401

What is a common method to prevent **bacteria buildup** in humidifiers?

Answer 401

Use manually inserted tablets or biocide ## Footnote The frequency of adding tablets depends on the manufacturer's instructions and water evaporation.

Question 402

Where should an **air washer** be installed for optimal maintenance?

Answer 402

On the suction side of the fan ## Footnote This positioning helps maintain a pressure slightly below atmospheric pressure to avoid water leakage.

Question 403

What must the **spray water** be heated above when using an air washer for humidification?

Answer 403

The dew point temperature of the entering air ## Footnote This ensures effective humidification and control over air temperature and humidity.

Question 404

What happens if the **spray water** is cooled below the dew point temperature?

Answer 404

Cooling and dehumidification occur ## Footnote This process can lead to undesirable humidity levels in the air.

Question 405

Name one method to maintain the **spray water** at the desired temperature.(3)

Answer 405

* Recirculate part of the spray water and add hot or cold water as needed * Mount a heating or cooling coil in the sump of the washer * Use a heat exchanger for recirculated spray water ## Footnote These methods ensure the spray water remains at the required temperature for effective humidification.

Question 406

What is a **steam grid humidifier** used for?

Answer 406

Injecting steam into the supply air stream ## Footnote This method is effective for humidification when steam is available.

Question 407

What is the recommended steam pressure range for a **steam grid humidifier**?

Answer 407

35 kPa to 70 kPa (5.1 to 10.2 psi) ## Footnote This pressure range prevents splashing of condensate and excessive temperature increases in the supply air.

Question 408

What is the simplest form of a **steam grid humidifier** composed of?

Answer 408

A perforated pipe wrapped with suitable felt wicking ## Footnote This design includes a drain pan to catch condensate droplets.

Question 409

What is the main function of a **steam grid humidifier**?

Answer 409

To supply steam to the air stream, adding moisture ## Footnote The steam is supplied to the steam jacket of the distribution manifold.

Question 410

In a steam grid humidifier, what role does the **baffle** in the separating chamber serve?

Answer 410

Knocks down any condensate formed in the supply line or manifold ## Footnote This condensate collects in the drain leg, where it is removed by the trap.

Question 411

What is the purpose of the **control valve** in a steam grid humidifier?

Answer 411

Regulates the supply of steam to the manifold ## Footnote The control valve operates at a pressure slightly above atmospheric.

Question 412

How does the **re-evaporating chamber** function in a steam grid humidifier?

Answer 412

Re-evaporates any liquid separated from the steam ## Footnote It is surrounded by steam in the separating chamber, which has a higher pressure and temperature.

Question 413

What is the significance of the **distribution manifold** in a steam grid humidifier?

Answer 413

Distributes low-pressure steam into the air stream ## Footnote It is completely surrounded by the supply steam flowing through the jacket.

Question 414

What feature does the **electrically heated pan humidifier** include for safety?

Answer 414

Low water cut-off switch ## Footnote This protects the heating element from damage.

Question 415

What is the maximum steam pressure for accurate humidity control in a **steam heated pan humidifier**?

Answer 415

103 kPa (15 psi) ## Footnote It should be used with a modulating control valve.

Question 416

What is an **actuator**?

Answer 416

A device used to position dampers and control valves ## Footnote Actuators play a crucial role in controlling various mechanical systems.

Question 417

Define **contact** in the context of electric control systems.

Answer 417

The electric switch configuration of a relay, controller, contactor motor arrangement ## Footnote Contacts can be normally open (NO) or normally closed (NC).

Question 418

What are **normally open (NO)** contacts?

Answer 418

Contacts that complete circuits when a relay is energized ## Footnote NO contacts are essential for certain control operations.

Question 419

What are **normally closed (NC)** contacts?

Answer 419

Contacts that complete electric circuits when a relay is de-energized ## Footnote NC contacts are used in safety and control applications.

Question 420

What is a **control valve**?

Answer 420

A device used to control the flow of fluid or gas such as water, air, or steam ## Footnote Control valves are critical in various industrial processes.

Question 421

What is the function of a **controller**?

Answer 421

A device that reacts to pressure, temperature, or humidity to provide control of an actuator or relay ## Footnote Controllers can provide two-position, floating, or proportioning control.

Question 422

What is a **damper**?

Answer 422

A device used to control the flow of air in a duct or through a wall louvre ## Footnote Dampers are important for HVAC systems.

Question 423

What does **line voltage** refer to?

Answer 423

The normal electric supply voltage ## Footnote Line voltage is essential for the operation of electrical devices.

Question 424

Define **linkage** in electric control systems.

Answer 424

A device that connects an actuator to a damper or control valve ## Footnote Linkages are crucial for mechanical movement in control systems.

Question 425

What is meant by **extra low voltage**?

Answer 425

Wiring or electric devices using 30 volts or less ## Footnote Extra low voltage systems are often used for safety and control applications.

Question 426

What is a **relay**?

Answer 426

A device consisting of a solenoid coil, which operates load carrying contacts when the coil is energized ## Footnote Relays are used for switching and control in electric circuits.

Question 427

What is the purpose of a **transformer**?

Answer 427

A device used to change AC voltage from one value to another ## Footnote Transformers are essential for voltage regulation in power systems.

Question 428

What is the primary function of a **thermostat** in a heating system?

Answer 428

To maintain the temperature of a heated space or substance at the desired level ## Footnote It regulates the heat supply.

Question 429

Name the **types of thermostats** based on their application.(6)

Answer 429

* Bimetal * Remote bulb * Immersion (aquastat) * Duct * Modulating * Multi-position ## Footnote These classifications depend on various factors including the type of temperature sensing element used.

Question 430

What is a **bimetal thermostat**?

Answer 430

A thermostat with a bimetal sensing element that reacts to changing room temperature and operates a two-position electric switch ## Footnote It regulates the heat supply by opening and closing the circuit.

Question 431

Describe the **construction** of a bimetal sensing element.

Answer 431

Consists of a strip made up of two thin layers of different metals that expand at widely different rates when heated ## Footnote One end is fixed while the other is free to move, operating an electric switch.

Question 432

What happens when the room temperature is **below** the thermostat setting?

Answer 432

The bimetal strip is straight and the contacts of the switch are closed, energizing the controlled device ## Footnote This allows the heat supply to operate.

Question 433

When does the **bimetal strip** bend?

Answer 433

When the room air warms up, causing the metals to expand at different rates ## Footnote This bending action opens the contacts of the switch.

Question 434

What is the purpose of a **heat anticipator** in thermostats?

Answer 434

To prevent the temperature of the room air from overshooting the set temperature of the thermostat ## Footnote It provides timed, two-position action.

Question 435

What type of switches are used in **heavy-duty thermostats**?(2)

Answer 435

* Mercury switches * Snap switches ## Footnote These switches open and close instantly to prevent burning of the contact points.

Question 436

What is the **operating range** of a sensitive thermostat?

Answer 436

Between 10°C and 32°C (50°F to 90°F) ## Footnote The required temperature is set by adjusting a lever on top of the thermostat.

Question 437

Fill in the blank: The **bimetal strip** can be shaped in the form of a _______ to accommodate a longer strip.

Answer 437

coil or a spiral ## Footnote This allows for compact design while increasing free end movement.

Question 438

What is the purpose of a **Remote Bulb Thermostat**?

Answer 438

To control the temperature of air in ducts or liquids in tanks or boilers ## Footnote Designed for use with line voltage or low voltage; can also be used as limits or alarms in systems.

Question 439

What does the term **volatile liquid** refer to?

Answer 439

A substance that readily expands and can vaporize on the application of heat ## Footnote Used in the sensing bulb/capillary tube/bellows combination of thermostats.

Question 440

What is the function of an **Immersion Thermostat (Aquastat)**?

Answer 440

To sense and control the temperature of water or other liquids in boilers, piping, tanks, etc. ## Footnote The sensing element is liquid filled and actuates the switch based on temperature changes.

Question 441

What is the main function of a **Duct Thermostat**?

Answer 441

To control air temperatures in ducts and plenums ## Footnote Contains a bimetal sensing element protected by an open metal guard tube.

Question 442

How does a **Modulating Thermostat** differ from a simple on-off thermostat?

Answer 442

It adjusts the position of the controlled device in direct proportion to heat demand ## Footnote Uses a special regulatory mechanism, such as a variable potentiometer.

Question 443

What is the operation of a **Multi-Position Thermostat** similar to?

Answer 443

An on-off thermostat ## Footnote Equipped with two or more switches that operate in sequence, each controlling part of the heat supply.

Question 444

What type of sensing element does an **Immersion Thermostat** use?

Answer 444

Liquid filled sensing element ## Footnote It expands and contracts with temperature changes to actuate the switch.

Question 445

The **Remote Bulb Thermostat** operates based on the expansion of what?

Answer 445

A volatile liquid ## Footnote The increase in pressure from vaporization expands the bellows to operate the control switch.

Question 446

The **room thermostat** should be mounted at what height above the floor?

Answer 446

1.5 m (60 in) ## Footnote It is important for the thermostat to sense the average temperature of the area to be heated.

Question 447

Where should the **thermostat** be located to ensure proper air circulation?

Answer 447

On an inside wall ## Footnote It should be in the path of natural air circulation when the heating system is off.

Question 448

List locations to **avoid** when installing a thermostat.(7)

Answer 448

* Behind doors * Behind furniture * Behind drapes * In cold drafts from doors and windows * Next to concealed ducts or piping * In direct rays of sun or fireplace * Near warm air outlets, lamps, radios, TV sets, or other sources ## Footnote These locations can affect the thermostat's ability to accurately sense temperature.

Question 449

What is a **humidity controller** also known as?

Answer 449

Humidistat ## Footnote It measures the relative humidity of air in a room or an air duct.

Question 450

What type of element does a **humidistat** use to sense humidity?

Answer 450

Hygroscopic element ## Footnote This element consists of moisture-sensitive nylon strands that change length with humidity.

Question 451

How does a **humidistat** control the operation of a humidifier?

Answer 451

By activating a controller mechanism ## Footnote It can function as a switch for on-off control or a potentiometer for modulating control.

Question 452

What happens when the required **relative humidity** is reached?

Answer 452

The humidistat opens the contacts of the switch ## Footnote This stops the operation of the humidifier.

Question 453

What are the two classes of **pressure controllers**?

Answer 453

* High-pressure controllers * Low-pressure controllers ## Footnote They measure and control different pressure ranges.

Question 454

What do **high-pressure controllers** measure?

Answer 454

High pressures or vacuum measured in kPa or mm of mercury ## Footnote Examples include steam or water pressures in an air conditioning system.

Question 455

What do **low-pressure controllers** measure?

Answer 455

Low pressures and vacuums measured in mm of water ## Footnote They are used for different applications compared to high-pressure controllers.

Question 456

In a pressure controller, one side of the diaphragm is exposed to what?

Answer 456

The pressure to be controlled ## Footnote The other side is in contact with a reference pressure.

Question 457

What happens to the diaphragm in a pressure controller when the measured static pressure drops?

Answer 457

The diaphragm rises, lifting the main lever ## Footnote This action causes the branch pressure to drop.

Question 458

What is the purpose of the **adjustable orifice** in the pressure controller?

Answer 458

To limit the volume of air that the controller has to process ## Footnote This helps stabilize the controller's operation.

Question 459

What is the function of **controlled devices** in electric control systems?

Answer 459

Perform a certain function in response to the signal of the controller ## Footnote Examples include controlling fuel valves, electric radiator valves, and dampers.

Question 460

Name one type of **controlled device** that an electric thermostat may control. (6)

Answer 460

* Fuel valve in the supply line to the burner of a furnace or boiler * Electric relay that switches the circulator in a hydronic system * Electric radiator valve in the supply line to steam or hot water convectors * Three-way mixing valve controlling the temperature of the water supply * Three-way diverter valve controlling water flow to a heating system * Damper motor operating air louvres ## Footnote These devices respond to the thermostat's signals to regulate heating.

Question 461

What type of control does an **electric radiator valve** provide?

Answer 461

Two-position (on-off) control of steam or hot water ## Footnote The valve and actuator form one assembly, with a small electric motor that opens the valve when energized.

Question 462

What is the purpose of a **motor-operated valve** in heating systems?

Answer 462

Modulating or two-position control of steam or hot water supply lines ## Footnote It ensures tight shutoff and consists of a reversible driving motor and reduction gears.

Question 463

Describe the structure of a **three-way valve**.

Answer 463

A double-seated valve with three ports ## Footnote It allows flow between different ports depending on the position of the valve plug.

Question 464

What is the purpose of a **three-way valve** in hydronic heating systems?

Answer 464

Regulate the heat supply to all or part of the heating system ## Footnote It can be used for mixing service or divert service.

Question 465

In a **three-way valve** used for mixing service, what does it do?

Answer 465

Mixes cooler return water with heated water from the boiler ## Footnote This results in a constant flow of supply water at varying temperatures to meet heat demand.

Question 466

What is the purpose of a **three-way valve** in heating systems?

Answer 466

To divert the flow of water to bypass the heat exchanger, reducing heat supply to match reduced heat demand ## Footnote This allows for better control of heating based on demand.

Question 467

What is a **capacitor-type control motor** used for?

Answer 467

For valve and damper operation ## Footnote It can provide two-position, floating, or modulating control.

Question 468

Fill in the blank: The **capacitor-type control motor** is usually built with the rotor and gear train sealed in a housing partly filled with _______.

Answer 468

oil ## Footnote This design eliminates the need for further lubrication during service.

Question 469

What are the three types of control provided by a **capacitor-type control motor**?

Answer 469

* Two-position * Floating * Modulating ## Footnote These types allow for different levels of control in heating systems.

Question 470

What is the **first step** in the operating sequence of a basic electric control circuit in a warm air heating system?

Answer 470

The thermostat senses a drop in air temperature below the set point temperature ## Footnote The thermostat acts as the controller in this system.

Question 471

What happens after the thermostat senses a drop in air temperature?

Answer 471

The thermostat switch closes to send an electric signal ## Footnote This action initiates the control sequence.

Question 472

What is the role of the **electric wire** in the basic electric control circuit?

Answer 472

It serves as the connecting link to transmit electric current to the burner ## Footnote The electric wire is crucial for connecting the controller to the controlled device.

Question 473

What is the **controlled device** in a warm air heating system?

Answer 473

The burner ## Footnote The burner is responsible for raising the temperature of the heat transfer medium.

Question 474

What does the burner do in the heating system?

Answer 474

It starts up, raising the temperature of the heat transfer medium (air) ## Footnote This process transfers heat to the air in the building.

Question 475

What does the thermostat do after the burner raises the air temperature?

Answer 475

It senses the increase in air temperature ## Footnote This sensing is part of the feedback mechanism in the control system.

Question 476

What occurs when the air temperature reaches the thermostat's setting?

Answer 476

The thermostat switch opens and the burner shuts down ## Footnote This action completes the control cycle and maintains the desired temperature.