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These 10 free HPSC questions are organized by exam domain, so you can see how each part of the Heat Pump Service Certification blueprint is tested. Reveal the answer and explanation under each question.
An air-source heat pump has an accumulator in the common suction line, just ahead of the compressor. During a changeover from heating to defrost, what is the accumulator's principal protective role?
Correct answer: D - Limit liquid entering the compressor while allowing oil return.
Immediately after a thermostat replacement, a heat pump cools on a heating call and heats on a cooling call. The outdoor unit requires its reversing-valve solenoid to be energized for cooling. Testing shows that the new thermostat supplies 24 VAC to O/B during heating, but not during cooling. What correction addresses the cause?
Correct answer: A - Configure the O/B output to energize during cooling.
A dual-fuel installation is approved for alternating heat-pump and gas-furnace operation, not simultaneous heating. At 5°F outdoors, the heat pump's documented maximum output is 24,000 Btu/h and the house loses 30,000 Btu/h. The furnace can meet the full load. Although the heat pump is approved to operate down to −13°F, indoor temperature is falling while it runs at maximum capacity with normal readings. Which control response fits this installation?
Correct answer: A - Transfer heating to the furnace with the compressor off.
A homeowner reports that the outdoor fan stopped while the compressor continued running on a damp, cold morning. A brief whooshing sound was followed by a white vapor cloud, with no burning odor. Frost melted from the outdoor coil, and four minutes later the fan restarted and normal heating resumed. The homeowner asks whether to leave the system off. What is the appropriate advice?
Correct answer: D - Keep normal heating selected; the observations match a completed defrost cycle.
During a stabilized cooling test on an R-407C heat pump, the pressure-temperature chart gives a bubble-point temperature of 33°F and a dew-point temperature of 44°F at the measured evaporator-outlet pressure. An insulated probe at the same location reads 56°F. The specified evaporator-outlet superheat range is 10-14°F. Which service finding is correct?
Correct answer: B - Superheat is 12°F; this reading does not justify a TXV adjustment.
Before replacing an inverter board, a technician locks out every supply and verifies zero AC voltage at the unit's incoming terminals. The manufacturer's waiting period has elapsed, but a correctly rated meter still reads 286 VDC across the DC bus. How should the technician proceed?
Correct answer: C - Maintain lockout, use the specified discharge procedure, and verify that hazardous DC voltage is absent.
A commissioning test measures 9.6 kW of net heat delivered indoors. At the same operating condition, the compressor draws 2.7 kW, the indoor blower 0.3 kW, and the outdoor fan 0.2 kW of electrical power. Resistance heat is off and other electrical loads are negligible. The operating heating coefficient of performance for the complete system is closest to:
Correct answer: A - 3.0
A compressor-contactor control rung is wired in this order: Y → high-pressure switch → low-pressure switch → contactor coil → C. During a steady compressor call, measurements to C are 24.6 VAC at Y, 24.6 VAC between the two pressure switches, and 0 VAC between the low-pressure switch and the coil. Coil continuity and the common return have been verified with power isolated. What do these readings establish, without assuming the reason?
Correct answer: B - The low-pressure switch is open.
A fixed-speed heat pump is losing cooling capacity. Outdoor air is 90°F, and indoor airflow is correct. Evaporator-outlet superheat is 32°F and condenser-outlet subcooling is 19°F; the manufacturer's targets under these conditions are 10°F for each. Matched, insulated probes read 96°F immediately before the liquid-line filter-drier and 77°F immediately after it. Which fault best fits this combination?
Correct answer: C - A restriction in the liquid-line filter-drier.
The complaint on a ductless inverter heat pump is 'the outdoor unit hardly ever shuts off.' In mild weather, room temperature stays at setpoint. Compressor speed follows a 28 Hz command and rises to 65 Hz during the manufacturer's higher-output test, with a corresponding increase in heating output. No alarms or out-of-range readings are found. What belongs in the service conclusion?
Correct answer: D - Normal part-load modulation; no repair is indicated.
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