Heat Pump

Overview

An air-source heat pump moves heat between indoors and outdoors using a vapor-compression refrigerant cycle, and reverses that cycle to either heat or cool a building from a single machine. Because it transports heat rather than generating it, a heat pump delivers several units of heating or cooling per unit of electrical input, making it far more efficient than resistive heating.

The system splits across two units: the Outdoor Unit containing the compressor and refrigerant controls, and the Indoor Air Handler indoors, joined by a Refrigerant Lineset. Operation is directed by the Main Control Board and set at the Thermostat.

How it works

The inverter-driven scroll compressor in the Outdoor Unit raises refrigerant pressure and temperature. A 4-way reversing valve decides direction: in cooling, the outdoor coil rejects heat and the indoor coil absorbs it; in heating, the roles swap. An electronic expansion valve meters refrigerant into the low-pressure side, where it boils and absorbs heat. The compressor is protected by a suction accumulator, a liquid receiver, and a filter-drier, and the whole circuit is charged with R-410A.

Indoors, the Indoor Air Handler passes return air across the evaporator coil with an ECM blower, then delivers it to the ducts; an electric heat strip supplements capacity in deep cold, and a defrost sensor lets the system periodically melt frost off the outdoor coil. The variable-speed compressor is fed by an inverter drive board that synthesizes variable-frequency power from an IGBT bridge.

The two units exchange refrigerant through the insulated Refrigerant Lineset, while the Main Control Board coordinates compressor speed, fan, reversing valve, and defrost in response to commands from the Thermostat.