Heat Pumps Flashcards
6 cards from real NATE practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Heat Pumps flashcards as text
What component allows a heat pump to reverse the refrigeration cycle between heating and cooling modes?
Answer: Reversing valve
The reversing valve redirects refrigerant flow so the indoor coil acts as a condenser in heating mode and an evaporator in cooling mode.
At what outdoor temperature do most standard air-source heat pumps reach their balance point?
Answer: 35–40°F
The balance point is typically 35–40°F, where the heat pump output equals the building heat loss and auxiliary heat is not yet needed.
What is the purpose of the accumulator in a heat pump system?
Answer: Prevent liquid refrigerant from entering the compressor
The accumulator is located on the suction line and traps liquid refrigerant, allowing only vapor to reach the compressor.
During a heating cycle, which coil in a heat pump acts as the evaporator?
Answer: Outdoor coil
In heating mode, the outdoor coil absorbs heat from the outside air (acting as evaporator) and the indoor coil releases heat (acting as condenser).
What initiates a defrost cycle on an air-source heat pump?
Answer: Time/temperature or pressure differential control sensing frost buildup on outdoor coil
Defrost controls typically use a combination of time and outdoor coil temperature (or pressure differential) to trigger defrost when frost accumulates.
What does COP (Coefficient of Performance) measure for a heat pump?
Answer: Ratio of heat output to electrical energy input
COP is the ratio of heat energy delivered to electrical energy consumed; a COP of 3 means 3 units of heat per 1 unit of electricity.