HVAC

Question 1

An electronic thermostat combines the features of which 2 devices?

Answer 1

An electronic timer and thermostats

Question 2

A 240 V line voltage thermostat is used to control the household heating apparatus. When marked in the “off” position, it must disconnect.

Answer 2

The ground conductor

Question 3

What are the three type of residential thermostats are:

Answer 3

Line voltage, low voltage and electronic

Question 4

Thermostats are not allowed to have a marked “_____” unless they ____________ in the heating branch circuit

Answer 4

OFF, open all ungrounded conductor

Question 5

What type of heater is normally installed at ceiling height?

Answer 5

Unit heat

Question 6

What type of electric heater unit can be used with certain oiled-fired, forced-air furnaces

Answer 6

Plenum heater

Question 7

What is the usual “watts per unit length” rating of standard density baseboard heaters?

Answer 7

820W/m

Question 8

What type of heater is normally installed at cieling height?

Answer 8

Unit Heater

Question 9

Residential water heaters are commonly available from in _____ and _____ ratings.

Answer 9

3kW, 4.5kW

Question 10

What are the three types typws of thermonstats commonly usws in residential space heating applications?

Answer 10

• line voltage thermostats
• low voltage thermostats
• electronic thermostata

Question 11

The typical efficiency of gas fired furnace is between ____ to ____

Answer 11

70% to 80%

Question 12

Which does the room thermostat control directly, the gas valve or the blower motor?

Answer 12

The gas valves

Question 13

After the thermostats contacts open, which shuts off first, the blower motor or the gas burner?

Answer 13

Gas burner

Question 14

What is the purpose of the anticipator resistor in the room thermostats?

Answer 14

To limit the set point overshoot to an acceptable value

Question 15

What is a thermostats?

Answer 15

Thermostats are temperature-actuated switches.

Question 16

Thermostats are not allowed to have a marked “OFF” position.
True or false

Answer 16

True, unless they open all ungrounded conductors in the
heating branch circuit when the control is switched to the “OFF” position, so in most cases a SPST thermostat will be marked “low” or “minimum” instead of “Off.

Question 17

What type of thermostats act as on/off switches to conduct full power to the heater.

Answer 17

Line-Voltage thermostats

Question 18

What type of thermostats has low voltage and uses semiconductor components for both temperature sensing and control-circuit switching?

Answer 18

Electronic Thermostats

Question 19

No matter what type is selected, room thermostats should be mounted approximately ___________ above the floor and located centrally on an inside wall away from drafts, direct sunlight,
and sources of heat.

Answer 19

1.5 m (5 ft.)

Question 20

What type of thermostats are used primary for high-amperage electric heating systems and operate on a 24 V power source supplied by a transformer.

Answer 20

Low-voltage thermostats

Question 21

What type of heater that are easy to install and provide heat by gently warming the air from floor to ceiling?

Answer 21

Baseboard Heater?

Question 22

Heating elements are normally rated in:

Answer 22

120, 208, 240, 277, 347 and 600V

Question 23

Baseboard heaters are commonly available in ______ increments starting from ______.

Answer 23

250 W, 500 W

Question 24

Standard density heaters are usually rated at __________.

Answer 24

820 W/m (250 W/ft.)

Question 25

Electric heaters commonly use resistance wires such as ________, which generate heat when conducting currents

Answer 25

nichrome

Question 26

Where baseboard heaters should be installed?

Answer 26

at floor level, centred along the walls and preferably under windows or other areas of high heat loss. Although it seems counter intuitive to place them on a cold wall or right under a window, it is the most efficient place for them.

Question 27

Baseboard does have fan and haves other method to move to air. True or False

Answer 27

False, baseboard heat does not have a fan or have other method to move to air.

Question 28

The panel is 120/240 V single phase, and is of the standard __% rated equipment.

Answer 28

80%

Question 29

What type of heater contain heating element, blower fan, and usually come with louvres and diffuser to direct air flow

Answer 29

Unit heater diffuser -an accessory that directs and distributes the heated air. louvres -adjustable vent.

Question 30

Unit heaters are generally available from _____kW to ___kW. For for single phase AC it is up to ____kW

Answer 30

2kW to 60kW 5kW

Question 31

How can unit heater be installed?

Answer 31

The unit heater can be suspended from a ceiling or wall, or recessed into a wall

Question 32

The Canadian Electrical Code (CEC) states that the hot air flow should not be directed onto any surface such that it will reach temperatures in excess of 85°C True or False

Answer 32

False, such that it will reach temperatures in excess of 90°C

Question 33

Units heater should be mounter at least _______ from the sidewalk

Answer 33

450mm

Question 34

What is the wattage and voltage rating of electric furnace?

Answer 34

Electric furnaces are available in sizes from 5 kW to 40 kW, with voltage ratings of 240 V or 208 V

Question 35

How can electric furnace should be installed

Answer 35

Electric furnaces are compact and can be installed horizontally or vertically. They can be floor mounted or suspended from ceilings.

Question 36

where are Gas-fired forced-air furnace usually located?

Answer 36

The furnace is usually located in the basement or crawl space of a house.

Question 37

What is another word for heat exchanger?

Answer 37

Plenum

Question 38

In multiple unit installation the air should flow in a circular motion along the exposed wall. true or false

Answer 38

True

Question 39

Units should be at least ______ from the side walls

Answer 39

450 mm

Question 40

what is electric heater?

Answer 40

electric furnace is composed of a blower-heater combination, which is forces hot air through ductwork via floor registers.

Question 41

what is a thermocouple?

Answer 41

A thermocouple consists of two dissimilar metals connected together to form a circuit

Question 42

A single thermocouple develops a voltage of about ____ to ____ direct current (DC) millivolts

Answer 42

25 to 30 DC millivolts

Question 43

In a gas burner, the source of heat for the thermocouple is the ________.

Answer 43

Pilot light

Question 44

More than one thermocouple connected in series is a ________,

Answer 44

Thermopile

Question 45

The power output of a thermopile is greater than that of a single thermocouple—typically either _________ or ________.

Answer 45

250 or 750 DC millivolts

Question 46

How does gas-fired forced-air furnace work?

Answer 46

A fans draws return air from the living/dining room area, passes it through the heat exchanger

Question 47

ome use a direct spark ignition (DSI) to ignite the burners, others an electrically heated hot-surface igniter similar to a diesel engine glow plug, while others use a continuously burning pilot light to ignite the burners

Answer 47

Gas fired furnace

Question 48

In most furnaces, the blower control and overheat safety thermostats are on one device. The typical settings for this unit are:

Answer 48

* Blower off at 32°C ( 90°F) * Blower on at 54°C (130°F) * High limit off at 104°C (220°F)

Question 49

What is an electronic air cleaner

Answer 49

An electronic air cleaner is an optional furnace peripheral that uses electrostatic action to remove very small particles of dust, pollen and smoke that pass right through a standard filter. These filters are installed in the return air duct of the furnace, preferably downstream of the standard filter.

Question 50

what is an humidifier?

Answer 50

Humidifiers are another type of furnace ducting peripheral. They are designed to increase the humidity through evaporating or misting water into the plenum.

Question 51

Electronic air cleaner , often the voltages used internally in these units will be quite high, which creates two dangers:

Answer 51

- Danger from electrical shock. - Danger from ozone accumulation.

Question 52

What type of heater that are similar to duct heaters in basic construction, but they are installed directly in the up flow vertical duct (plenum) of certain oil-fired, forced-air furnaces.

Answer 52

Plenum heaters

Question 53

what heater work in tandem with the fuel-burning furnace to provide the primary heat, and use the fuel combustion when the electric elements alone cannot keep up with the heat demand

Answer 53

Plenum heater

Question 54

What is a heating cable? where are they usually use?

Answer 54

Resistance cables can be installed in ceilings or floors to form radiant heating systems that are completely hidden. Commonly used under tile floors for radiant heating.

Question 55

For floor warming, the cable is usually installed at a spacing of about ____ mm to ____ mm if it is loose cable installed onsite

Answer 55

150mm to 300mm

Question 57

Residential electric heaters are generally available in two tank ratings:

Answer 57

3 kW and 183 L (40 Imperial gallons) and 4.5 kW and 273 L (60 Imperial gallons).