NATE: Heat Pump Troubleshooting
On an air-to-air heat pump system, the suction pressure and discharge pressure are low
during the cooling months. What are two possible problems: - ANS-a restricted indoor
metering device and a dirty air filter
On an air-to-air heat pump system, the discharge pressure and suction pressure are
high during the heating months. What are two possible problems: - ANS-a dirty indoor
filter and noncondensables in the system
A service call is made on an air-to-air heat pump system during the winter. When
servicing the system, it is found that the outdoor coil has frost buildup and the system is
operating on emergency heat. Technician A says that the system might have a defrost
problem. Technician B says that the reversing valve might be leaking. Which technician
is correct: - ANS-technician A
A service call is made on an air-to-air heat pump system during the winter months. The
technician arrives on the job and notices that the discharge pressure is low and the
suction pressure is high. What two problems could cause this symptom: - ANS-a leaking
reversing valve and bad compressor valves
How can a system be tested to determine if the reversing valve solenoid is leaking
internally: - ANS-A temperature measurement can be taken at the inlet and the outlet of
the valve in the heating and cooling mode
What component must always be de-energized during the defrost cycle on a heat pump:
- ANS-the outdoor fan
When an air-to-air heat pump is in the cooling mode, what can cause a decrease in
high-side and low-side pressure: - ANS-a restricted indoor metering device
Technician A says that the check valves in a heat pump system are located in series
with both metering devices. Technician B says that the check valves in a heat pump
system are located in parallel with both metering devices. Which technician is correct: -
ANS-Both technicians are correct
, A service technician notices that a check valve needs to be replaced in a heat pump
system. Because it is a ball-type check valve, it is critical for him to install the valve: -
ANS-vertically, with the seat on the bottom of the valve
After troubleshooting a heat pump system, the technician concludes that the check
valve is defective. He connects a recovery system and removes the refrigerant from the
unit. He then proceeds to unseat the old check valve and remove it from the system. He
cleans the area where the new valve will be installed, places it into position, and brazes
it into the system while not protecting the valve. After a thorough evacuation, he starts
the system and notices that the new valve is defective. What could have been the
problem with the new valve: - ANS-A heat sink was not used and the valve warped+The
valve may have been defective from the factory+The problem was misdiagnosed
Technician A says that the auxiliary heaters found on an air-to-air heat pump are used
to increase the system's pressure during a defrost cycle. Technician B says that the
auxiliary heaters found on an air-to-air heat pump are used to increase supply-air
temperature for comfort during a defrost cycle. Which technician is correct: -
ANS-technician B
When a heat pump switches into the defrost cycle, it must: - ANS-remain in defrost until
the outdoor coil has reached a predetermined temperature
A defrost termination thermostat is commonly located: - ANS-on the outdoor coil, and
opens at 55° F
Temperature split refers to: - ANS-the temperature difference between the air entering a
coil and the temperature of the coil
Technician A says that the outdoor ambient thermostat commonly de-energizes the
compressor during the second stage of heating in an air-to-air heat pump. Technician B
says that the outdoor ambient thermostat used with an air-to-air heat pump commonly
energizes the auxiliary strip heaters during the first stage of heating. Which technician is
correct: - ANS-Both technicians are incorrect
If there is malfunction in a hold-back thermostat that is used with an air-to-air heat
pump, how would this affect the system: - ANS-The system would not stay energized
during defrost if the room thermostat is satisfied. This could cause freezing of the
outdoor coil.
On an air-to-air heat pump system, the suction pressure and discharge pressure are low
during the cooling months. What are two possible problems: - ANS-a restricted indoor
metering device and a dirty air filter
On an air-to-air heat pump system, the discharge pressure and suction pressure are
high during the heating months. What are two possible problems: - ANS-a dirty indoor
filter and noncondensables in the system
A service call is made on an air-to-air heat pump system during the winter. When
servicing the system, it is found that the outdoor coil has frost buildup and the system is
operating on emergency heat. Technician A says that the system might have a defrost
problem. Technician B says that the reversing valve might be leaking. Which technician
is correct: - ANS-technician A
A service call is made on an air-to-air heat pump system during the winter months. The
technician arrives on the job and notices that the discharge pressure is low and the
suction pressure is high. What two problems could cause this symptom: - ANS-a leaking
reversing valve and bad compressor valves
How can a system be tested to determine if the reversing valve solenoid is leaking
internally: - ANS-A temperature measurement can be taken at the inlet and the outlet of
the valve in the heating and cooling mode
What component must always be de-energized during the defrost cycle on a heat pump:
- ANS-the outdoor fan
When an air-to-air heat pump is in the cooling mode, what can cause a decrease in
high-side and low-side pressure: - ANS-a restricted indoor metering device
Technician A says that the check valves in a heat pump system are located in series
with both metering devices. Technician B says that the check valves in a heat pump
system are located in parallel with both metering devices. Which technician is correct: -
ANS-Both technicians are correct
, A service technician notices that a check valve needs to be replaced in a heat pump
system. Because it is a ball-type check valve, it is critical for him to install the valve: -
ANS-vertically, with the seat on the bottom of the valve
After troubleshooting a heat pump system, the technician concludes that the check
valve is defective. He connects a recovery system and removes the refrigerant from the
unit. He then proceeds to unseat the old check valve and remove it from the system. He
cleans the area where the new valve will be installed, places it into position, and brazes
it into the system while not protecting the valve. After a thorough evacuation, he starts
the system and notices that the new valve is defective. What could have been the
problem with the new valve: - ANS-A heat sink was not used and the valve warped+The
valve may have been defective from the factory+The problem was misdiagnosed
Technician A says that the auxiliary heaters found on an air-to-air heat pump are used
to increase the system's pressure during a defrost cycle. Technician B says that the
auxiliary heaters found on an air-to-air heat pump are used to increase supply-air
temperature for comfort during a defrost cycle. Which technician is correct: -
ANS-technician B
When a heat pump switches into the defrost cycle, it must: - ANS-remain in defrost until
the outdoor coil has reached a predetermined temperature
A defrost termination thermostat is commonly located: - ANS-on the outdoor coil, and
opens at 55° F
Temperature split refers to: - ANS-the temperature difference between the air entering a
coil and the temperature of the coil
Technician A says that the outdoor ambient thermostat commonly de-energizes the
compressor during the second stage of heating in an air-to-air heat pump. Technician B
says that the outdoor ambient thermostat used with an air-to-air heat pump commonly
energizes the auxiliary strip heaters during the first stage of heating. Which technician is
correct: - ANS-Both technicians are incorrect
If there is malfunction in a hold-back thermostat that is used with an air-to-air heat
pump, how would this affect the system: - ANS-The system would not stay energized
during defrost if the room thermostat is satisfied. This could cause freezing of the
outdoor coil.
