HEAT PUMP FREQUENTLY ASKED QUESTIONS

• Heating Mode: A heat pump extracts heat from the outside air (even in cold weather) and moves it indoors.
• Cooling Mode: It removes heat from indoors and releases it outside.

 Heat pumps are efficient because they transfer heat instead of generating it. Key metrics include:

• COP: Compares heat transferred to electrical power input.
• EER: Cooling efficiency.
• HSPF: Heating efficiency over a season.
• SEER: Cooling efficiency over a season.

• Refrigerant: Absorbs, transports, and releases heat, changing phases (liquid, gas, vapor).
• Reversing Valve: Switches refrigerant flow between heating and cooling modes.
• Coils: Heat transfer between refrigerant and air.
• Evaporator: Where refrigerant absorbs heat indoors.
• Compressor: Compresses refrigerant, raising its temperature.
• Condenser: Releases heat outdoors.
• Expansion Device: Lowers refrigerant pressure and temperature.
• Outdoor Unit: Transfers heat to/from the outdoor air.
• Indoor Coil: Transfers heat to/from indoor air.
• Plenum: Distributes air in ducted systems.

 Expansion Device: Low-pressure liquid turns into vapor.

1. Outdoor Coil (Evaporator): Absorbs outdoor heat.
2. Compressor: Compresses vapor, raising its temperature.
3. Indoor Coil (Condenser): Transfers heat indoors. As it gets colder outside, heat pumps lose efficiency and need supplemental heating.

• Expansion Device: Low-pressure liquid turns into vapor.
• Indoor Coil (Evaporator): Absorbs heat indoors.
• Compressor: Compresses vapor, raising its temperature.
• Outdoor Coil (Condenser): Releases heat outdoors. The system also dehumidifies air.

 In cold weather, frost may build on the outdoor coil, reducing efficiency. The defrost cycle:

• Switches to cooling mode to melt frost.
• Turns off the outdoor fan to help melt frost faster.
• Uses demand-frost control (activates only when needed) or time-temperature defrost (set intervals).

 Single-Speed: Operates at a fixed capacity, meeting minimum efficiency standards.

• Variable-Speed: Adjusts capacity to match heating/cooling needs for better efficiency.
• Cold Climate Heat Pumps: Designed for colder areas, they have higher efficiency and better performance at low temperatures.

Proper sizing is crucial. A professional should calculate heating and cooling needs using a recognized method. An undersized system uses more supplemental heat, while an oversized system may cause inefficiency and discomfort.