Heat Pumps Flashcards

What is a typical symptom of an overcharged heat pump during cooling mode?

Answer: High suction pressure and high discharge pressure

Overcharge floods the evaporator with excess liquid refrigerant, raising suction pressure, and increases condenser load, raising discharge pressure.

During defrost mode, why does the indoor electric heat strip energize?

Answer: To temper the cool air being delivered while the system is in cooling mode for defrost

During defrost the refrigerant cycle reverses to cooling mode, delivering cold air indoors; auxiliary strips energize to prevent occupant discomfort.

A heat pump's outdoor unit is making a hissing noise and the reversing valve solenoid is energized. What is the most likely cause?

Answer: Reversing valve internal bypass (leaking internally)

An internally leaking reversing valve allows high-pressure refrigerant to bypass to the low-pressure side, causing a hissing sound.

What is the recommended method for charging a heat pump system in heating mode?

Answer: Charge by subcooling measured at the outdoor coil liquid line

In heating mode, the outdoor coil is the condenser, so subcooling at the outdoor liquid line is the correct charging method.

Which component on a heat pump prevents refrigerant from backing up into the compressor during the off cycle?

Answer: Accumulator

The accumulator collects liquid refrigerant on the suction side during shutdown and prevents liquid slugging when the compressor restarts.

What is a dual-fuel heat pump system?

Answer: A heat pump paired with a gas furnace that automatically switches to gas heat below a set outdoor temperature

Dual-fuel systems use the heat pump for mild weather and switch to the gas furnace when outdoor temperatures drop below the economic balance point.