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WorksheetsHeat Pump Review
Total questions: 100
Worksheet time: 50mins
An air-to-air heat pump has many of the same components as an air conditioning system. The major difference is that a heat pump also has a (an):
evaporator.
condenser.
reversing valve.
thermostatic expansion valve.
What is the difference between "demand defrost" and "timed defrost?"
Demand defrost depends on a manual action, and timed defrost depends on how cold it is outside.
Demand defrost senses temperature difference across the coil, and timed defrost is signaled by the time clock.
Demand defrost depends on a low-pressure control and timed defrost has an electric defrost heater.
Demand defrost happens only when needed and timed defrost is based on time/temperature.
The thermostat that controls the auxiliary electric heat according to the outdoor temperature is called the;
auxiliary temperature control.
outdoor auxiliary thermostat.
outdoor ambient thermostat.
hold in thermostat.
The outdoor temperature at which the heat pump provides the same amount of heat as the heat loss of the conditioned space without auxiliary heat is known as the;
initial balance point.
second balance point.
initial capacity point.
initial efficiency point.
At what temperature is an outdoor ambient thermostat normally set?
At 32 degrees Fahrenheit.
Slightly above the initial balance point.
The same as the Indoor thermostat.
15 degrees above the initial balance point.
The outdoor coil is frozen solid on a "no heat" service call. The most likely reason is;
the indoor fan is inoperative.
the unit is overcharged.
the unit is functioning on Auxiliary heat.
the outdoor fan is inoperative.
In order to determine a heat pumps' balance point, you must first calculate;
the building's heat load.
the consumption of kilowatts at 32 degrees.
the EER of the unit during a particular season.
the brand name of the compressor.
When a heat pump is used for heating and cooling, the system is sized by the;
heating load.
cooling load.
heating and cooling loads combined.
difference between the heating and cooling loads.
A high efficiency heat pump system designed to function from high to low ambient conditions below 10°F, may have?
two outdoor coils with each one incorporating a dual stage compressor.
two indoor coils with parallel metering devices.
an auxiliary heat exchanger injected with an ethylene glycol solution.
two compressors which operate in series.
Room thermostats for heat pumps should be installed;
as far away from the main return air grill as possible.
as near to the main return air grill as possible.
on an outside (cold) wall.
near an exit door or near a window.
When the heat pump compressor has malfunctioned, the customer has the option to switch the system to;
auxiliary heat mode.
emergency heat mode.
1st stage heat mode.
2nd stage heat mode.
Start-up with a night set back digital thermostat requires the technician to always;
set the secondary heat anticipator.
de-energize any heat anticipator.
de-energize the thermostat to protect the circuit, until the customer is proficient in its use.
teach the customer how to program the thermostat.
The heat pump defrost board can be manipulated by the technician to;
monitor system pressures.
program the thermostat.
simulate the defrost cycle.
reverse fan rotation.
The air-to-air heat pump outdoor unit is most efficient if located;
in a cold climate.
toward the prevailing wind.
in a confined area.
in a moderate climate zone.
Which of the following are innovations that may be found on new high efficiency units?
Electric defrost systems.
Higher compression ratios.
Automatic pump-down.
ECM fan motors.
How may a lockout (impedance) relay be reset?
Just push the reset button. They are all manual reset.
The technician has to fix the unit before reset.
Simply disconnect power to the unit momentarily.
The lockout relay automatically resets after 15 minutes.
The temperature difference between the 1st and 2nd bulbs for heating on a heat pump thermostat is:
dependent on ambient temperature.
260 F, if the ambient temperature is not known.
approximately 2° F.
there is no temperature difference.
SEERs calculated by:
The Seasonal Energy Efficiency Ratio.
Dividing the BTUs removed by the watts consumed during the cooling season.
How highly efficient the unit is verses cost of the unit.
Heat produced divided by voltage rating on the compressor.
If the indoor fan is operated at an excessive speed in the cooling mode:
the system will not properly remove the humidity from the conditioned space.
the system will not get the conditioned space cool enough.
the second stage of the thermostat can override the first stage.
the outdoor coil may become frosted.
The most preferred method of charging any system in the field is:
vapor into the suction line (unless it's a blend).
liquid into the suction line if it is a blend.
by weight.
superheat and sub cooling.
What is the industry standard for deep vacuum?
Pump it down for 3 hours.
Triple evacuate with nitrogen.
Maintain 500 microns for 15 minutes.
Maintain 200 microns for 10 minutes.
Good service practice for installation of a reversing valve includes:
use a hacksaw to remove the old valve.
use locking pliers to hold the new valve body while brazing.
to prevent oxidation while brazing, purge the system with refrigerant.
use heat paste and wet rags while brazing in the new valve.
Off-cycle crankcase heat is provided by:
one leg of supply voltage is directed through the start winding.
a dual run capacitor, which allows a small amount of current to flow through the windings.
a small amount of current is passed through the start capacitor to heat the start winding.
the crankcase heater is wired to an intermittent timer.
You are checking for proper airflow in CFM on a three ton heat pump system. The system has one return grill measuring 24" x 24", which has a net free area of 3.4 square feet. You measure air velocity and calculate an average of 400 FPM. From this information you can conclude that:
airflow in CFMs above normal range.
airflow in CFMs within normal range.
airflow in CFM is below normal range.
this is not enough information to calculate airflow.
What control operates the 1st stage of secondary heat?
The 1st outdoor thermostat.
The peak hours of power consumption in your area.
The second heating stage of the indoor thermostat.
High fire on the gas valve.
What is the industry standard for maximum duration for defrost?
As long as it takes to get the ice off the coil.
15 minutes if it's hard ice.
A maximum of 10 minutes.
A maximum of 30 minutes.
What is the recommended CFM across the evaporator coil of a heat pump?
600 to 700 CFM.
400 to 450 CFM.
200 to 300 CFM.
150 to 225 CFM.
If manufacturers specifications are not available, a good way to calculate cubic feet per minute through a coil is to:
Use temperature rise on emergency heat mode.
Assume 450 CFM per minute for all heat pumps.
Multiply the horsepower of the motor times the sq. circumference of the blower wheel.
Use temperature rise in cooling mode.
What type of defrost is employed on this heat pump?
Pressure-time initiation, temperature termination.
Time and temperature initiation, time or temperature termination.
Time or temperature initiation, time and temperature termination.
Pressure initiation, temperature termination.
Which component is responsible for energizing auxiliary heat during the defrost cycle?
The defrost time clock.
The reversing valve relay.
Heater relay
The defrost relay.
When this unit switches to the heat mode, select the sequence of events which will take place.
The RVR coil is energized through TH-1. The CR coil is energized through the RVR contacts.
The reversing valve relay is de-energized by N.C. contacts of the DFR, and HR-2 is energized through DTC-2.
The CR N.O. contacts close energizing the C coil, which in turn sends the hot gas into the indoor coil and meters liquid to the outdoor coil.
The CR N.C. contacts close energizing the C coil, which in turn sends the hot gas into the indoor coil and meters liquid to the outdoor coil.
The DTC motor and cam will close the DTC N.O. contacts momentarily (approx. 5 seconds). How is the DFR kept energized when the DTC N.O. contacts open?
The RVR contacts will be closed in the heating mode, which keep it energized.
The DTC N.O. contacts close during defrost and the DFR N.C. contacts open.
The DFR N.O. contacts close, which forms a holding circuit.
It is the specially designed impedance coil in the circuit that keeps the coil energized.
How is defrost terminated in this system?
The air pressure sensor contacts open, indicating the coil is defrosted.
The defrost thermostat is warm enough to open, normally 35°F or below.
The defrost time clock has closed the circuit after 20 minutes of defrost.
Either the time or temperature termination requirements has been satisfied.
Where is the LLP physically located in the system on this heat pump?
On the suction line before the reversing valve.
On whichever line is the suction line in the cooling mode.
On the liquid line before the reversing valve.
On the bi-flow liquid line located between the two coils.
You are starting-up a split system heat pump for the first time. The outdoor ambient temperature is 60°F. You check the temperature split across the indoor coil in the heat mode and find it is 38°F. You switch to cooling mode and determine a temperature split of 29°F. The most likely corrective action (relative to airflow) is;
lower the indoor fan speed.
decrease the outdoor fan speed
increase the outdoor fan speed.
increase the indoor fan speed.
Heat pump heating mode efficiency is rated in:
BTUs
HSPF.
AFUE.
SEER.
On a water source heat pump, the heat mode water regulating valve must be:
2 way.
3 way.
direct acting.
reverse acting.
An R22 heat pump operating in the heating mode has a suction pressure 50 psig and head pressure of 285 psig has a compression ratio of:
4.6:1.
3.2:1.
5.7:1.
7.7:1.
Which type of heat pump does not require a defrost cycle?
Air to air.
PTAC.
Window unit.
Water source.
An R-410A heat pump operating in the cooling mode has a suction pressure of 129 psig. Adding 2 psig for pressure drop in the coil, the true outlet pressure is 131 psig. The temperature of the suction line at the outlet of the evaporator is 57 F. What is the superheat?
43 degrees.
24 degrees.
19 degrees.
12 degrees.
On a time initiation / temperature termination defrost, the defrost time clock has one N.O. and one N.C. switch. When do the positions of these switches change?
Every time the defrost timer is energized.
Every 30 or 90 minutes, depending on the cam installed in the timer.
When the pressure switch senses a blocked coil.
Every hour, depending on the time of day.
What would be the result of closing registers in rooms that are uninhabited while operating in the heating mode?
The total airflow will increase, making some occupied areas warm.
The suction pressure will drop and the temperature will rise decreasing life span of the unit.
You will save on energy costs due to the decreased load on the compressor.
The discharge pressure and temperature will rise decreasing the life span of the unit.
What is the most common complaint from a customer changing from gas heat to a heat pump?
Cold air at high velocities coming out of the registers.
The lights on the thermostat are distracting.
low side wall registers.
Really cold condenser air.
When a heat pump is operating in the heat mode, the suction line at the compressor will feel;
luke warm.
hot.
near ambient temperature.
cold and sweaty.
The use of a scroll type compressor on a heat pump can eliminate the need for a;
reversing valve.
charge compensator.
defrost cycle.
suction line accumulator.
A heat pump operates satisfactorily in the cooling mode, but not in the heat mode. This could be caused by;
fan not operating properly.
low outdoor temperature.
high outdoor temperature.
a stuck check valve or clogged TXV screen.
It is not always a good idea to immediately connect a standard gauge manifold set and hoses to a heat pump when a problem is suspected because;
most technicians cannot read a gauge correctly.
gauges are never accurate.
the charge is critical, sometimes to ± 1/2 oz. refrigerant.
a gauge manifold set is very expensive and should be used sparingly.
Which component is responsible for changing the direction of the flow of refrigerant?
Thermostatic expansion valve.
capillary tube.
Reversing valve.
Check valve.
Some heat pump systems use a __________ as a metering device.
AEV / capillary tube
low side float
inverted flow control
fixed orifice
The slide valve and piston in the reversing valve is actuated by pressure directed through the;
solenoid and pilot valve.
defrost thermostat.
defrost timer.
outdoor thermostat.
During the heating cycle, the outdoor coil is use as;
the condenser.
the evaporator.
a receiver.
an accumulator.
During the cooling cycle, the indoor coil becomes;
the condenser.
the evaporator.
a receiver.
an accumulator.
During the defrost cycle, the outdoor fan is usually:
set to high speed.
set to low speed.
turned off.
run in reverse.
Heat pump systems which use a thermostatic expansion valve at each coil will also have:
a by-pass lines with check valves.
a capillary tube parallel to the liquid line.
the TXV sensing bulb connected to the liquid line.
pressure switch for each TXV.
Refrigerant flow through the compressor;
is normal in the heat mode and reversed in the cooling mode.
is normal in the cooling mode and reversed in the heat mode.
is always the same regardless of operating mode.
can be either direction depending on operating mode.
Because of the possibility of liquid flood-back, a heat pump that uses a reciprocating compressor should be equipped with a;
suction receiver.
crankcase pressure valve.
liquid receiver.
suction accumulator.
A scroll type compressor;
is more susceptible to damage from liquid flood-back.
is less susceptible to damage from liquid flood-back.
can be operated in either direction, which makes it well suited for heat pumps.
is not well suited to heat pump applications.
On split a system heat pump, a "no heat / no cooling" service call, you turn the thermostat to the fan on / cont position and the indoor fan operates. This action verifies that;
the compressor is operable.
the system has proper air flow.
there is a high voltage supply to the outdoor unit.
the transformer is functioning.
On most air-to-air heat pumps;
the Indoor and outdoor coils are the same size physical and capacity.
the indoor and outdoor coils are of different physical size and capacity.
airflow must be reduced over the indoor coil during the cooling mode.
airflow must be reduced over the indoor coil during the heat mode.
A heat pump system, operating at 45 F ambient, may be _______ efficient than electric resistance heat.
just as
3 to 4 times more
8 to 10 times more
2 to 3 times less
Since electric resistance heat provides 1 watt of usable heat for each watt of energy purchased, electric resistance heat has a COP of:
1:1
2:1
3:1
1:2
As outside ambient air temperature decreases, a heat pump's COP;
increases
decreases
remains the same.
fluctuates up and down.
During the defrost cycle, the system switches to the ______ mode.
heating
pump down
emergency heating
cooling
During the heating mode, the refrigerant in the indoor coil is under;
low pressure
high pressure
atmospheric pressure
a vacuum
What three things happen on most air-to-air heat pumps during defrost?
The outdoor fan must run, the indoor fan must stop, and the time guard circuit must be energized.
The compressor shuts off, superheated air comes out of the registers, and a strange smell fills the conditioned space.
The reversing valve must switch to cooling mode, the outdoor fan shuts off and auxiliary heat is energized.
The reversing valve must switch to heating mode, the indoor fan shuts off and auxiliary heat is energized.
High suction pressure and low discharge pressure on a heat pump system operating in either the heating or cooling mode can be an indication of;
overheated compressor motor windings.
a stuck closed check valve.
compressor inefficiency.
a restricted metering device.
The preferred method to perform adjustments to the refrigerant charge in a heat pump system is in the ______ mode.
heat
cooling
defrost
emergency heat
You answer a service call for insufficient heat. You find the suction pressure is higher and discharge pressure is lower than normal. Using a digital thermometer, you measure the line entering the reversing valve from the compressor discharge and find 215°F. You then measure the line leaving the reversing valve that connects to the indoor coil and find 185°F. These readings are an indication of;
a damaged compressor.
a faulty reversing valve.
a stuck defrost relay.
a low refrigerant charge.
The customer complaint is not enough heat. You install service gauges and find the low side pressure is higher than normal and the high side pressure is lower than normal. You switch the system to the cooling mode and find the pressures are normal. The most likely cause of the problem is;
a stuck open check valve at the outdoor coil.
a stuck open check valve at the indoor coil.
defective compressor valves.
a stuck closed check valve at the outdoor coil.
A customer complains that their heat pump system blows cool air periodically during the heat mode. This could be caused by;
a stuck defrost relay (does not energize the aux. heat during the defrost mode).
an undersized indoor coil.
a oversized outdoor coil.
thermostat set to emergency heat.
When a heat pump is in the heating mode, what can cause frost accumulation on the outdoor coil when the ambient temperature is 45°F?
The outdoor coil is colder than the ambient air.
45°F air contains a high percentage of moisture that will freeze.
More cold air is being removed from the conditioned space.
The indoor fan is clogged.
The indoor fan on a heat pump system operates;
through a temperature controlled fan switch.
at the same speed for heating or cooling.
in the same manner as a gas or oil heating system.
at a low speed for heating and high speed for cooling.
The defrost cycle can be initiated by;
pressure drop across the indoor coil.
pressure rise across the outdoor coil.
time and temperature.
the outdoor thermostat.
The defrost cycle can be terminated by;
pressure drop across the indoor coil
pressure rise across the outdoor coil.
time / temperature
the outdoor thermostat
Movement of the piston in the reversing valve is accomplished by;
adding compressor discharge pressure to both sides of the piston.
removing compressor discharge pressure from both sides of the piston.
bleeding pressure from one side of the piston to the suction side of the compressor.
solenoid coil.
Some close coupled (package unit) heat pumps use an electronic expansion valve to meter refrigerant. One advantage to using an electronic expansion valve is:
electronic expansion valves operate at reduced head pressure.
electronic expansion valves can meter refrigerant in either direction.
electronic expansion valves do not require a filter-drier.
no auxiliary heat needs to supplement heat pump.
Liquid line filter/driers that are used on heat pump systems;
are designed with four connectors for connection to 4 way valves.
must be installed in conjunction with bi-flow check valves.
must be installed in series with check valves.
must be a bi-flow design if used without check valves.
When installing the heat pump outdoor unit, care should be taken to provide for drainage during the cycle.
heating
cooling
defrost
emergency heat
The indoor coil is usually mounted in the air stream __ the auxiliary electric heat strips.
before
after
parallel to
downstream of.
On Dual Fuel Systems, the indoor coil must be located;
before the heat exchanger.
after the heat exchanger.
in the heat exchanger.
parallel to the heat exchanger.
Air-to-air heat pumps are most practical to operate in areas where the lowest winter temperature does not go below __ F.
+10
-20
-10
-30
Air-to-air heat pumps, operating without auxiliary heat, provide air to the registers that is approximately __ F or less.
100
140
160
200
The most common method of defrosting the outdoor coil on an air source heat pump is;
auxiliary electric heaters
supply air
exhaust vent air
reverse cycle defrost.
COPs the abbreviation for;
Coefficient of performance
Common operating procedure
Cost of performance
Coefficient of power
At temperatures above 45 degrees F, the heat pump refrigeration cycle permits the:
condenser to release 3 to 4 times more heat than it takes in electrical energy to drive the compressor.
evaporator to release 3 to 4 times more heat than it takes in electrical energy to drive the compressor.
compressor to pump 3 to 4 time more refrigerant in the heating mode than in the cooling mode.
condenser to absorb 3 to 4 times more heat than it takes in electrical energy to drive the compressor.
In addition to heat from the outdoor coil, a heat pump in the heating mode will get heat from;
solar.
adhesion.
reactance.
compression.
When operating in the heat mode, hot gas leaves the compressor and first flows to;
the outdoor coil.
the indoor coil.
the accumulator.
the reversing valve.
When operating in the cooling mode, hot gas leaves the compressor and first flows to;
the outdoor coil.
the indoor coil.
the accumulator.
the reversing valve.
To make the reversing valve slide move, the system must have a pressure difference of;
10 to 20 psig.
25 to 40 psig.
75 to 100 psig.
160 to 200 psig.
Before connecting a manifold gauge set to a heat pump system, you should first;
make sure the customer understands that there may be a de-minimums loss of refrigerant.
check the superheat.
check the head pressure.
verify the operating mode of the system.
In the heat mode, the suction line entering the compressor contains;
high pressure / low temperature liquid.
low pressure / high temperature liquid.
low pressure / low temperature vapor.
high pressure / high temperature vapor.
The reversing valve is often referred to as a;
two-way valve.
three-way valve.
four-way valve.
non-discriminating valve.
A heat pump has a thermostatic expansion valve (TEV) and a check valve at each coil. When the modes are reversed;
the check valves insure the system will work even if the reversing valve fails.
the TEVs will direct the refrigerant to the check valves.
refrigerant will bypass the TEV on the coil serving as the condenser.
refrigerant will bypass the TEV on the coil serving as the evaporator.
Mechanically troubleshooting a reversing valve can be done by;
checking the pressure difference between the low and high side of the system.
by checking the temperature differential between the connection serving the low side.
checking for the correct voltage to the pilot solenoid.
touching the valve body at the connection serving the high side with the system off.
Compressors designed for heat pumps differs from compressors designed for A/C in that;
it is built with smaller bearing surfaces.
it must move a higher volume at lower pressures of refrigerant.
it must accommodate refrigerants at higher specific gravities.
it is designed to operate at high compression ratios.
One of the most important devices to insure the longevity of a heat pump's reciprocating compressor is the;
high or low pressure switch
pressure relief valve
crankcase heater
reversing valve
A heat pump can be difficult to charge properly because;
A. heat pumps can only be charged in the cooling mode.
B. heat pumps can only be charged in the heating mode.
C. heat pumps require that the system is off and the refrigerant is weighed in.
D. of low ambient conditions.
High efficient heat pump systems charged with R-410A refrigerant normally use a;
fixed orifice metering device for the heating and cooling cycle.
fixed orifice metering device for the heating cycle and a TXV for the cooling cycle.
TXV metering device for the heating and a fixed orifice metering device cooling cycle.
AXV metering device for the heating and a fixed orifice metering device cooling cycle.
When a heat pump is operating in the cooling mode, the;
refrigerant is by-passing the indoor metering device and the indoor check valve is open
refrigerant is by-passing the indoor metering device and the indoor check valve is closed.
indoor metering device is metering refrigerant and the outdoor check valve is open.
outdoor metering device is metering refrigerant and the outdoor check valve is closed.
When in the cooling mode, the low pressure refrigerant vapor leaves the reversing valve and travels to the;
indoor coil and then to the outdoor coil.
accumulator and then to the compressor.
compressor and then to the accumulator.
accumulator and then to the indoor coil.
