1
Q
The Four-Way Reversing Valve
- Allows heat pump to pump heat in ___ directions
- Diverts heat-laden discharge gas to either ____ or cool in conditioned space
- Refrigerant is directed from the _______ to the indoor coil in the heating mode
- Refrigerant is directed from the compressor to the ______ coil in cooling mode
A
- two
- heat
- compressor
- outdoor
2
Q
The Four-Way Reversing Valve: Control and Operation
- Controlled by the space temperature _________
- Four port valve that has a slide mechanism in it:
- Position of the slide determines the mode of operation: heating or cooling
- Smaller, direct-acting, four way reversing valves
- pressure difference pushes the slide mechanism
A
thermostat
3
Q
What terminal is a conventional heat pump wired to?
A
B
4
Q
What terminal is a non-conventional heat pump wired to?
A
O
5
Q
Default/fail to O means ?
A
heating
6
Q
Gas line in heat pump:
- HIGH temp superheated gas means the unit is in what mode?
- LOW temp superheated gas means the unit is in what mode?
A
- heating mode
2. cooling mode
7
Q
Water Coils:
- Heat transfers between refrigerant from indoor coil and water from water loop
- Installed near indoor ____
- Refrigerant and water pumped in separate but _______ tubes
A
- coil
3. adjacent
8
Q
Water Loop:
- Tubing running to and from water _____
- Tubing is submerged in ______
- Used in closed-loop water-based systems
- Tubing water does not mix with body of _____ or refrigerant
A
- coil
- water
- water
9
Q
Auxiliary Heat: Balance point:
- When heat pump output _____ heat loss of the conditioned space
- If heat loss is greater than heat production, ________heat is required
A
- equals
2. auxiliary
10
Q
Auxiliary Heat:
- Supplementary heat source in order to temper air
- Usually electric resistance heating coils, but it could be a gas-fired or oil-fired heating system
- Also used during reverse cycle ______ and for emergency heat operation
A
- defrost
11
Q
During defrost of outdoor coil the unit will go into cooling mode in order to bring hot gas back to outdoor unit in order to melt the ___
A
ice
12
Q
The Air-to-Air Heat Pump:
- The air-to-air heat pump resembles the central air-conditioning system
- Changes in terminology in a heat pump system:
- the coil that serves the inside of the house is called the ______ coil
- the coil that is located outside the house is called the _____ coil - Mode determined by the direction in which the _________ flows
A
- indoor, outdoor
3. refrigerant
13
Q
Refrigerant Line Identification:
- The larger line is called the gas line because it always carries ___
- The suction line in the cooling mode and the discharge line in the heating mode
- The smaller line is called the liquid line because only liquid ________ travels through it
- The liquid flow toward the inside unit in ______ and towards the outside unit in _______
A
- gas
- refrigerant
- summer, winter
14
Q
Metering Devices:
- Metering devices needed at _____ heat exchanger
- Types used in heat pumps;
_____-orifice devies
_________ tubes
____
Flow ____ pistons
A
- each
2. fixed orifice, capillary, TXVs, flow check
15
Q
Metering Devices:
- Specially designed for ____ ____ applications
- There must be a metering device at the ______ unit in the heating mode
- There must be a metering device at the indoor coil in _______ mode
A
- heat pumps
- outdoor
- cooling
16
Q
Thermostatic Expansion Valves:
- Check valves are piped parallel to the TXV to allow refrigerant to bypass the control when needed
- in cooling mode, the valve needs to meter the flow of liquid refrigerant into the indoor coil
- in heating mode, the liquid needs to move freely toward the outdoor unit - A vapour-charged TXV with a limited charge in the bulb usually used
- Bidirectional thermostatic expansion valves have a _____ valve built in
A
- check
17
Q
In any type of hot pull down you need an ___ TXV
A
MOP - maximum operating pressure
18
Q
Thermostatic expansion valves:
- Generally allow flow in only ___ direction
- Solutions for more flow directions;
Check valves running ______ to each TXV - Must have ___ compatible with coil and compressor
A
- one
- parallel
- MOP
19
Q
The Capillary Tube:
- Often encountered on older pieces of equipment
- Will allow refrigerant flow to ____ ways
- Typically two capillary tubes are used
- Check valves are used to reverse flow but cannot meter flow based on ________ outlet temp (SH)
- Must be sized for specific flow amount
- Different sizes used for ______ and outdoor coils
A
- both
- evaporator
- indoor
20
Q
Combination of Metering Devices:
- Uses the capillary tube at the indoor coil
- used in the ______ mode
- Load is relatively _______ in the warmer months - Uses thermostatic expansion valve at the outdoor coil
used in the _______ mode
- allows system to reach maximum ________ quickly
A
- cooling, constant
2. heating, efficiency
21
Q
Electronic Expansion Devices:
- Can meter refrigerant in ____ directions
- If indoor and outdoor coils are close together, ____ device can be used
- The correct superheat will be maintained in both heating and cooing modes
A
- both
2. one
22
Q
Orifice metering devices:
- used in conjunction with _____ valves
- One device is located at each ____
- The bore at the indoor coil is ______ than the bore at the outdoor oil
- Normally used with a ______ filter drier
A
- check
- coil
- larger
- bi-flow
23
Q
Flow Check Pistons:
- Meters refrigerant flow in ___ direction
- Allows refrigerant to flow ______ and unrestricted in the other direction
- systems use two flow check pistons oriented in opposite directions
A
- one
2. freely
24
Q
Liquid Line Accessories:
- Two standard filter driers can be used on systems with check valves:
- only one drier In the circuit at a time
- they are installed with arrows pointing in the same direction as the _____ valves - Bi-Flow filter driers: use this for heat pumps
- two driers in one
- designed for ____ pump applications
A
- check
2. heat pump
25
Compressors:
1. Operate at ______ ambient temperatures than air-conditioning compressors
2. Designed to handle liquid _______
- slow start-up routines
- stronger valves
- accumulators and two-way filter-driers
- crankcase heaters
1. lower
| 2. liquid slugging
26
For low temp compressors the bore size is
larger
27
For medium temp compressors the bore size will be smaller and high temp bore size even
smaller
28
Heat pump compressors are designed to handle overloads in pressure during defrost mode so they do not need crankcase ______ regulators
pressure
29
Application of the Air-to-Air Heat Pump:
1. usually installed in ______ climates
- In winter, the outdoor coil ______ heat
2. The system loses capacity as the outside temperature ____
1. milder, absorbs
| 2. drops
30
Auxiliary Heat:
1. Required when the heat pump cannot provide all the heat a structure needs
- The heat pump is the primary heat source
- auxiliary heat could be ______, oil or gas
- electric heat is the most common auxiliary heat used
- as the outside temp drops, the structure requires more heat
electric
31
Balance Point:
1. Balance point occurs when the heat pump can pump in exactly as much heat as the structure is ______ out
2. Above the balance point, the heat pump will _____ on and off
3. Below the balance point, the heat pump will run _________ and second stage (auxiliary) heat will be energized
1. leaking
2. cycle
3. continuously
32
Heat Pump Efficiency:
1. Methods for gauging heat pump efficiency
- _____ efficiency ratio (EER)
- ________ energy efficiency ratio (SEER)
- ________ seasonal performance factor (HSPF)
- Coefficient of performance (COP)
energy, seasonal, heating
33
Coefficient of performance:
1. One watt of usable heat is supplied for each watt of energy purchased
- 100% efficient, COP is 1:1
2. Air-to-air heat pumps: a COP of 3:5:1
- one watt of electrical energy used by the compressor can furnish ____ watts of usable heat
2. 3.5 watts
34
Coefficient of Performance: Effect of Temperature;
1. High COP only occurs during ______ outdoor winter temperatures
2. A heat pumps COP falls as the outdoor temperature ____
3. A typical air-to-air heat pump has a COP of 1:5:1 at _F
1. higher
2. falls
3. 0F
35
The Defrost Cycle: SEER and HSPF
1. Seasonal energy efficiency ratio (SEER)
- the total cooling output for the system divided by the actual power _____
2. Heating Seasonal Performance Factor HSPF)
- applies to particular piece of equipment
3. SEER and HSPF ratings are results of federal _____ _______
1. input
| 3. energy policies
36
The Indoor Unit:
1. The part of the system that circulates the ___ within the structure
2. Contains the fan and coil and often the ______ strip heaters
3. The refrigerant coil must be located in the _______ before the auxiliary heating coil
4. The indoor unit may be a ___ or oil fired furnace
1. air
2. electric
3. airstream
4. gas
37
Coefficient of Performance: Water-to-air heat pumps;
1. Some manufacturers have controls to shut off the ________ at temperatures of 0-10F
2. Water-to-air heat pumps might not need auxiliary heat since the heat source (water). temperature is
3. Water-to-air heat pumps have a ____ rating as high as 4:1
1. compressor
2. constant
3. COP
38
The Split-Type, Air -to-Air Heat Pump:
1. Air-to-Air systems can be split or _______ type
2. Both heat pumps and cooling air-conditioning systems look identical
3. Split systems require the installation of the gas and liquid refrigerant lines to connect the ______ and outdoor units
1. package
| 3. indoor
39
The Indoor Unit: Furnace Types;
1. If gas or oil furnace is the indoor unit, the coil must be relocated in the outlet airstream of the furnace
2. If a gas or oil furnace is used, the heat pump will ___ operate while they run
3. Heat pumps added to electric furnaces should have the coil located ____ the heat strips
2. not
| 3. after
40
Temperature of the Conditioned Air:
1. Temperature of the air supplied by a HP are not as hot as with gas and oil-fired equipment
2. Leaving air temps are in the ___F range
3. Supply air temperature will ____ when outside air temperature drops
4. Proper air distribution can help reduce "____" complaints
2. 100F
3. fall
4. draft
41
The Outdoor Unit:
1. Must have good air conditions around it.
- prevailing winds affect ________
- In the winter, outdoor coil will collect moisture that ______
- Outdoor coil should be installed so it raises above the ground ___ to allow defrost water to run to the ground
- A defrost system defrosts the ___ from the outdoor coil
- performance
- freezes
- pad
- ice
42
Package Air-to-Air Heat Pumps:
1. Has all the sealed system and electrical components in one ______
2. Works much the same way as a packaged air-conditioning unit
3. Can accept different electric heat sizes
4. Require that ductwork be run right up to the ____
5. Supply and return ductwork must be ________
1. housing
4. unit
5. insulated
43
What does Y control in a heat pump?
the compressor to allow for cooling
44
Controls for Air-to-Air Heat Pumps:
1. Controls are ______ than other heating/cooling equipment
2. In a heat pump, there are two heating systems and one cooling system
3. Auxiliary heating system must be operated as a system by itself in case the heat pump _____
4. Auxiliary heat is referred to as ________ heat when used because of heat pump failure
1. different
3. fails
4. emergency
45
Controls for Air-to-Air Heat Pumps:
thermostat
1. The space thermostat is the key to controlling the system
2. Normally, a ____-stage heating and two-stage cooling thermostat is used
two
46
Controls for Air-to-Air Heat Pump: Cooling Cycle Control;
1. Automatic changeover thermostat
- Changes between ______/_______ modes
heating/cooling
47
Controls for Air-to-Air Heat Pumps: Space Heating control;
1. Space heating control
- thermostat controls compressor, outdoor fan motor, and ______ fan motor operation
- Excessively cold temperatures energizes _______-stage heat
- Second-stage heat _____ on and off to assist the heat pump
- indoor
- second
- cycles
48
Controls for Air-to-Air Heat Pumps:
Space Heating controls cont'd
1. Balance point: point at which the heat pump can satisfy the load without ______ down; may be multiple
2. Electric Heaters are energized at different temperatures:
- The goal is to only energize enough electric strip heaters as necessary to help the heat pump reach and maintain the desired space temp
1. shutting
49
Controls for Air-to-Air Heat Pumps: Electronic Thermostats;
1. Heat anticipator:
- found on heat pump thermostats an conventional thermostats
- most heat pump thermostats come with ____
2. Electronic thermostats:
- most have thermistors for heat-sensing, which responds _____ to temperature change
1. two
| 2. faster
50
The Defrost Cycle:
1. Defrosts ice from outside coil during heating mode
- when the outside temp drops the evaporator saturation temp can drop below __F
- The outdoor coil can begin to freeze; system performance ______
2. The need for defrost varies depending on outside air temperatures and conditions:
- the more moisture in the air, the more _____ that forms on coil
1. reduced
| 2. frost
51
The Defrost Cycle: How is defrost accomplished?
1. By de-energizing the outdoor fan and dour-way reversing valve switches into _______ mode
2. One stage of strip heat is turned on and system will ____/_____ at the same time
1. cooling
| 2. heat/cool
52
Initiating the defrost cycle:
1. manufacturers design systems to start defrost when frost affects _______
2. Some use ____ and ________ initiated system,s
3. Cylic is typically ___ minutes
1. performance
2. time and temperature
3. 90 mintes
53
Initiating the defrost cycle: air pressure switch initiated
1. Measures the air pressure drop across the outdoor coil
- When the unit begins to accumulate ice, a pressure drop occurs and the air with contacts _____
2. The combo of time and temp only ensures that time has passed and the coil is cold enough to accumulate _____
1. close
| 2. ice
54
The Defrost Cycle: Terminating defrost;
1. ____, _____, and pressure can all be used to terminate defrost
2. Temperature sensors used for the defrosting function will open at __F
3. __ minutes is the normal maximum time allowed for defrost cycle
1. time, temp
2. 50F
3. 10 mintes
55
The Defrost Cycle: Electronic Control of Defrost;
1. Electronic control of defrost
- electronic timers and thermistors used to control _____
- More accurate control than non-electric methods
- can incorporate _____ and temperature features into a single unit
2. Demand initiation when coil has reached __ to __% frosted over condition
- sensing the diff between the coil temp and ambient temp
- measuring the pressure drop across the coil
- sensing the coil temp
1. defrost, time
| 2. 50-60%,
56
Indoor Fan Motor Control:
1. With a heat pump, the blower must start at the beginning of the cycle
- controlled by the _______
- the indoor blower is started with the blower terminal, often labeled __
- The compressor operates whenever the unit is calling for cooling or heating
1. thermostat, G,
57
Second-Stage Electric Heat:
1. Accomplished with an _______ furnace with a heat pump coil for cooling and heating
2. Required to _____ the heat pump when it cannot provide all the heat the structure needs
3. Also used as ________ heat when the heat pump needs service
4. Heaters also energized during defrost
1. electric
2. help
3. emergency
58
Servicing the Air-to-Air Heat Pump:
1. Much like servicing a ______ system
2. During the cooling mode, operates as a high-temperature refrigeration system
3. During the heating mode, operates as low-temperature refrigeration system
4. Servicing of the system is divided into ________ and mechanical
1. refrigeration
| 4. electrical, and mechanical
59
Troubleshooting the Electrical System:
1. Typical electrical problems:
- indoor blower motor and outdoor fan motor
- compressor contractor, fan relays
- defrost relay
- compressor
- reversing valve solenoid
- electric strip heaters
- general wiring problems
remember*
60
Troubleshooting Mechanical Problems:
1. Can be hard to identify in a heat pump, particularly in ______ operation
2. _______ operation of a heat pump is similar to an air-conditioning unit
3. Mechanical problems are solved with gauge manifolds, wet-bulb and dry-bulb thermometers, and air-measuring instruments
1. winter
| 2. summer
61
Troubleshooting the Four-Way Reversing Valve:
1. Common problems: ____valve, defective coil, and internal leaks
2. Check to see if coil is _______, a warm coil indicates power is being supplied, place a screwdriver on coil surface to sense magnetic field
3. Check for voltage supplied to the coil
1. stuck
| 2. energized
62
Troubleshooting the Compressor:
1. A reliable test will tell whether the compressor is pumping at near capacity: operate the unit in _______ mode while blocking the _____ until head pressure is 440psig and the suction pressure is 118psig
2. amperage should be at close to ___ load
3. large inefficiencies indicate that the compressor is leaking ______
1. cooling, airflow
2. full
3. internally
63
Checking the Charge:
1. Most heat pumps have a _______ refrigerant charge
2. Do not install a standard ______ manifold each time you suspect a problem.
3. When a heat pump has a partial charge;
- leak check system before charging
- some manufacturers recommend evacuation and recharge
1. critical
| 2. gauge manifold
64
Special Applications for Heat Pumps; Use of oil or gas furnaces for auxiliary heat
1. more efficiency than auxiliary _____ heat
2. heat pump coil must be installed _______ of oil or gas heat exchanger
3. the air must flow through the furnace heat exchanger before the heat pump coil
4. the oil or gas furnace must ___ operate at the same time that the heat pump is operating
1. electric
2. downstream
4. NOT
65
Heat Pumps Using Scroll Compressors:
1. ideally suited for heat pump application because of its pumping characteristics
2. Scrolls do not lose as much ______ as reciprocating compressors
3. scroll compressor pressures are about the same as ________ compressors
4. scroll compressors are discharge gas ______
2. capacity
3. reciprocating
4. cooled
66
Heat Pumps Using Scroll Compressors: Other features;
1. Have a check valve in the discharge leaving the compressor to prevent pressures from equalizing through the compressor during the off cycle
2. normally do not require suction-line _______ because they are not as sensitive to liquid flood back
2. accumulator
67
Heat Pump Systems with Variable-Speed Motors:
1. Used for the compressor and both fan motors as a method to improve system _______ in heat pump systems
2. sized closer to the heating _______ of the structure at full load; will run at part load and reduced power in warmer months
1. efficiency
| 2. requirements
68
In BC, how are our heat pumps manufactured and configured?
Default to heating, non-conventional
69
How to improve humidity in a heat pump?
lower fan speed in cooling and high speed in heating
70
Why is oversizing a heat pump bad?
higher cost of equipment, installation, and less then ideal summer humidity control
Term 2: Heat Pumps
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