Heat Pump Technology Flashcards
7 cards from real HVAC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Heat Pump Technology flashcards as text
In a dual-fuel heat pump system, what determines when the gas furnace takes over from the heat pump?
Answer: Outdoor temperature drops below the economic or mechanical balance point
In a dual-fuel system, the gas furnace activates when the outdoor temperature drops below the balance point where the heat pump becomes less economical or loses capacity.
What is the purpose of check valves in a heat pump refrigerant circuit?
Answer: To ensure refrigerant flows through the correct expansion device depending on operating mode
Check valves allow refrigerant to bypass one expansion device while directing flow through the active device appropriate for the current heating or cooling mode.
Which of the following BEST describes a water-source heat pump (WSHP) loop configuration in a commercial building?
Answer: All units share a common water loop maintained between 60–90°F, with a cooling tower and boiler for temperature control
Commercial WSHPs share a common water loop maintained within an efficiency band, with a cooling tower rejecting excess heat and a boiler adding heat when needed.
A heat pump's outdoor fan motor fails during heating mode. What is the MOST likely result?
Answer: Suction pressure will drop and the system may trip on low-pressure cutout
Without outdoor fan airflow across the evaporating coil in heating mode, heat absorption drops, causing suction pressure to fall and potentially triggering a low-pressure safety cutout.
What is the significance of the 'lockout temperature' setting on a heat pump thermostat?
Answer: The outdoor temperature below which the heat pump compressor is locked out and only auxiliary heat operates
The lockout temperature prevents the heat pump from operating at extremely low outdoor temperatures where it would be inefficient or potentially damaging, relying solely on auxiliary heat.
What type of expansion device is most commonly used in modern variable-speed heat pump systems?
Answer: Electronic expansion valve (EEV/EXV)
Electronic expansion valves provide precise, electronically controlled refrigerant flow modulation that complements variable-speed compressor operation across a wide range of conditions.
A technician is checking a heat pump in cooling mode and finds high suction pressure and high discharge pressure with warm air from the supply. What does this MOST likely indicate?
Answer: Refrigerant overcharge or a dirty outdoor condenser coil
High pressures on both sides in cooling mode typically indicate an overcharge of refrigerant or a dirty condenser coil restricting heat rejection.