NATE AIR CONDITIONING AND HEAT PUMP FINAL PAPER
2025/2026 QUESTIONS WITH ANSWERS GRADED A+
✔✔Which component pumps refrigerant through the system and raises the vapor
temperature?
a. Accumulator
b. Compressor
c. Condenser
d. Evaporator - ✔✔b (Compressor)
✔✔How are hermetic compressor motors cooled?
a. With air drawn around the compressor shell by the condenser fan
b. With water circulated through tubing wrapped around the compressor shell
c. With suction vapor drawn from the evaporator
d. With a combination of air and water - ✔✔c (With suction vapor drawn from the
evaporator)
✔✔Heat pump compressors sometimes run hotter than compressors used in cooling-
only units because heat pump compressors ____.
a. exhibit low refrigerant density at low suction pressures during the heating cycle
b. pump liquid refrigerant during the cooling cycle
c. must prevent ice formation during the defrost cycle
d. must heat indoor spaces in the winter - ✔✔a (exhibit low refrigerant density at low
suction)
✔✔When is a crankcase heater most needed?
a. Early in the morning during the cooling cycle
b. When the compressor is operating in very cold winter weather
c. When the compressor is operating in very humid conditions
d. When the compressor is off - ✔✔d (When the compressor is off)
✔✔Work done on the refrigerant in the condenser is transferred as ____.
a. latent heat
b. sensible heat
c. specific heat
d. both sensible and latent heat - ✔✔d (both sensible and latent heat)
✔✔Why are more circuits needed in the outdoor coils used in heat pumps than in the
condenser coils used in cooling-only units?
,a. To keep the pressure drop across the outdoor coil high
b. To keep the pressure drop across the outdoor coil low
c. To provide more subcooling during the cooling cycle
d. To provide more subcooling during the heating cycle - ✔✔b (To keep the pressure
drop across the outdoor coil low)
✔✔What is the typical water flow rate per ton of cooling for water-source heat pumps
operating in closed-loop systems?
a. 3.0 gpm per ton
b. 2.5 gpm per ton
c. 2.0 gpm per ton
d. 1.5 gpm per ton - ✔✔a (3.0 gpm per ton)
✔✔What tool should be used to shorten a capillary tube?
a. A pair of pliers with side-cutter edges
b. A small tubing cutter
c. Any tubing cutter approved for use on refrigerant tubing
d. A triangular or knife-edge file - ✔✔d (A triangular or knife-edge file)
✔✔Which pressure in a TEV is the opening pressure?
a. Bulb pressure
b. Evaporator pressure
c. Spring pressure
d. A combination of bulb and spring pressures - ✔✔a (Bulb pressure)
✔✔What affect does a low refrigerant charge have on reversing valve operation?
a. It causes the slider to overheat
b. It creates a hissing sound in the reversing valve
c. It increases the chance that the reversing valve will not be able to transfer properly
d. It has no effect on reversing valve operation - ✔✔c (It increases the chance that the
reversing valve will not be able to transfer properly)
✔✔When adding a heat pump to an existing fossil-fuel furnace, an installer must do all
of the following except ____.
a. add a control to prevent the heat pump and furnace from operating at the same time
during normal heating
b. confirm there is adequate clearance around the outdoor section for good air flow
c. level the indoor coil's condensate pan to ensure proper drainage of condensate water
, d. make sure that the number of fins per inch of the new coils equals that of the
replaced coils - ✔✔d (make sure that the number of fins per inch of the new coils equals
that of the replaced coils)
✔✔What is the purpose of a receiver?
a. It prevents liquid refrigerant from slugging the compressor
b. It removes heat from refrigerant vapor
c. It returns oil to the compressor at a rate the compressor can tolerate
d. It stores liquid refrigerant - ✔✔d (It stores liquid refrigerant)
✔✔What is the typical storage life of modern refrigerants?
a. 5 to 10 years
b. 10 to 20 years
c. 20 to 30 years
d. Modern refrigerants have an indefinite storage life - ✔✔d (Modern refrigerants have
an indefinite storage life)
✔✔Which of the following should be used to leak-test refrigerant tubing?
a. Compressed air
b. Dry nitrogen
c. Oxygen
d. Water - ✔✔b (Dry nitrogen)
✔✔Of the motors commonly used in HVACR systems, which type has the lowest
starting torque?
a. PSC motor
b. Shaded-pole mole
c. Split-phase motor
d. Three-phase motor - ✔✔b (Shaded-pole motor)
✔✔What is the typical phase angle for a split-capacitor motor?
a. 15°
b. 30°
c. 75°
d. 90° - ✔✔b (30°)
✔✔What determines the staging of a two-speed compressor in a heat pump
application?
a. Deviation from setpoint of the thermostat
2025/2026 QUESTIONS WITH ANSWERS GRADED A+
✔✔Which component pumps refrigerant through the system and raises the vapor
temperature?
a. Accumulator
b. Compressor
c. Condenser
d. Evaporator - ✔✔b (Compressor)
✔✔How are hermetic compressor motors cooled?
a. With air drawn around the compressor shell by the condenser fan
b. With water circulated through tubing wrapped around the compressor shell
c. With suction vapor drawn from the evaporator
d. With a combination of air and water - ✔✔c (With suction vapor drawn from the
evaporator)
✔✔Heat pump compressors sometimes run hotter than compressors used in cooling-
only units because heat pump compressors ____.
a. exhibit low refrigerant density at low suction pressures during the heating cycle
b. pump liquid refrigerant during the cooling cycle
c. must prevent ice formation during the defrost cycle
d. must heat indoor spaces in the winter - ✔✔a (exhibit low refrigerant density at low
suction)
✔✔When is a crankcase heater most needed?
a. Early in the morning during the cooling cycle
b. When the compressor is operating in very cold winter weather
c. When the compressor is operating in very humid conditions
d. When the compressor is off - ✔✔d (When the compressor is off)
✔✔Work done on the refrigerant in the condenser is transferred as ____.
a. latent heat
b. sensible heat
c. specific heat
d. both sensible and latent heat - ✔✔d (both sensible and latent heat)
✔✔Why are more circuits needed in the outdoor coils used in heat pumps than in the
condenser coils used in cooling-only units?
,a. To keep the pressure drop across the outdoor coil high
b. To keep the pressure drop across the outdoor coil low
c. To provide more subcooling during the cooling cycle
d. To provide more subcooling during the heating cycle - ✔✔b (To keep the pressure
drop across the outdoor coil low)
✔✔What is the typical water flow rate per ton of cooling for water-source heat pumps
operating in closed-loop systems?
a. 3.0 gpm per ton
b. 2.5 gpm per ton
c. 2.0 gpm per ton
d. 1.5 gpm per ton - ✔✔a (3.0 gpm per ton)
✔✔What tool should be used to shorten a capillary tube?
a. A pair of pliers with side-cutter edges
b. A small tubing cutter
c. Any tubing cutter approved for use on refrigerant tubing
d. A triangular or knife-edge file - ✔✔d (A triangular or knife-edge file)
✔✔Which pressure in a TEV is the opening pressure?
a. Bulb pressure
b. Evaporator pressure
c. Spring pressure
d. A combination of bulb and spring pressures - ✔✔a (Bulb pressure)
✔✔What affect does a low refrigerant charge have on reversing valve operation?
a. It causes the slider to overheat
b. It creates a hissing sound in the reversing valve
c. It increases the chance that the reversing valve will not be able to transfer properly
d. It has no effect on reversing valve operation - ✔✔c (It increases the chance that the
reversing valve will not be able to transfer properly)
✔✔When adding a heat pump to an existing fossil-fuel furnace, an installer must do all
of the following except ____.
a. add a control to prevent the heat pump and furnace from operating at the same time
during normal heating
b. confirm there is adequate clearance around the outdoor section for good air flow
c. level the indoor coil's condensate pan to ensure proper drainage of condensate water
, d. make sure that the number of fins per inch of the new coils equals that of the
replaced coils - ✔✔d (make sure that the number of fins per inch of the new coils equals
that of the replaced coils)
✔✔What is the purpose of a receiver?
a. It prevents liquid refrigerant from slugging the compressor
b. It removes heat from refrigerant vapor
c. It returns oil to the compressor at a rate the compressor can tolerate
d. It stores liquid refrigerant - ✔✔d (It stores liquid refrigerant)
✔✔What is the typical storage life of modern refrigerants?
a. 5 to 10 years
b. 10 to 20 years
c. 20 to 30 years
d. Modern refrigerants have an indefinite storage life - ✔✔d (Modern refrigerants have
an indefinite storage life)
✔✔Which of the following should be used to leak-test refrigerant tubing?
a. Compressed air
b. Dry nitrogen
c. Oxygen
d. Water - ✔✔b (Dry nitrogen)
✔✔Of the motors commonly used in HVACR systems, which type has the lowest
starting torque?
a. PSC motor
b. Shaded-pole mole
c. Split-phase motor
d. Three-phase motor - ✔✔b (Shaded-pole motor)
✔✔What is the typical phase angle for a split-capacitor motor?
a. 15°
b. 30°
c. 75°
d. 90° - ✔✔b (30°)
✔✔What determines the staging of a two-speed compressor in a heat pump
application?
a. Deviation from setpoint of the thermostat
