NATE Heat Pump Troubleshooting Exam
and Answers
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: - ✔✔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: - ✔✔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: - ✔✔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: - ✔✔a leaking reversing valve
and bad compressor valves
How can a system be tested to determine if the reversing valve solenoid is leaking internally: -
✔✔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: -
✔✔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: - ✔✔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: - ✔✔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: - ✔✔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: - ✔✔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: - ✔✔technician B
When a heat pump switches into the defrost cycle, it must: - ✔✔remain in defrost until the
outdoor coil has reached a predetermined temperature
A defrost termination thermostat is commonly located: - ✔✔on the outdoor coil, and opens at
55° F
Temperature split refers to: - ✔✔the temperature difference between the air entering a coil
and the temperature of the coil
and Answers
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: - ✔✔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: - ✔✔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: - ✔✔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: - ✔✔a leaking reversing valve
and bad compressor valves
How can a system be tested to determine if the reversing valve solenoid is leaking internally: -
✔✔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: -
✔✔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: - ✔✔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: - ✔✔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: - ✔✔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: - ✔✔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: - ✔✔technician B
When a heat pump switches into the defrost cycle, it must: - ✔✔remain in defrost until the
outdoor coil has reached a predetermined temperature
A defrost termination thermostat is commonly located: - ✔✔on the outdoor coil, and opens at
55° F
Temperature split refers to: - ✔✔the temperature difference between the air entering a coil
and the temperature of the coil
