An air-to-air heat pump works by transferring heat between the outside air and the inside air to either heat or cool a building. Here's a simple breakdown:

1. Heating Mode (winter):

   • Even when it's cold outside, there is still some heat energy in the air.

   • The heat pump extracts that heat using a refrigerant that evaporates at low temperatures.

   • The refrigerant absorbs heat from the outside air, becomes a gas, and is compressed, which raises its temperature even more.

   • This hot refrigerant gas moves inside and releases its heat into the indoor air through a heat exchanger (basically like a radiator).

   • After releasing the heat, the refrigerant cools down, turns back into a liquid, and the cycle repeats.

2. Cooling Mode (summer):

   • The cycle is reversed.

   • The heat pump extracts heat from inside the building and releases it to the outside.

   • This cools down the indoor air, working like an air conditioner.

Main parts of an air-to-air heat pump:

• Outdoor unit: captures or dumps heat to the outside air.

• Indoor unit: releases or captures heat inside the house.

• Compressor: increases the pressure and temperature of the refrigerant.

• Expansion valve: lowers the pressure of the refrigerant so it can absorb heat again.