If you do not understand how A/C works read "Air Conditioning" first.
A heat pump is essentially an air conditioner with a few additions. A heat pump has a reversing valve, two metering devices and two bypass valves. This allows the unit to provide both A/C and Heat. The diagram above shows a HP (heat pump) in cool mode. The cycle goes like this;
- The compressor (1) pumps the refrigerant to the reversing valve (2).
- The reversing valve directs the flow to the outside coil (condenser) where the fan (3) cools and condenses the refrigerant to liquid.
- The air flowing across the coil removes heat (4) from the refrigerant
- The liquid refrigerant bypasses the first metering device and flows to the second metering device (6) at the inside coil (evaporator) where it is metered.
- Here it picks up heat energy from the air blowing (3) across the inside coil (evaporator) and the air comes out cooler (7). This is the air that blows into the home.
- The refrigerant vapor (8) then travels back to the reversing valve (9) to be directed to the compressor to start the cycle all over again (1).
The diagram above shows the heat pump in heat mode. The difference in the two diagrams is the reversing valve (2) directs the compressed refrigerant to the inside coil first. This makes the inside coil the condenser and releases the heat energy (3-4). This heated air is ducted to the home. The outside coil is used to collect the heat energy (3-7). This now becomes the evaporator.
Both heating and A/C modes do exactly the same thing. They PUMP HEAT from one location to another. In these examples the heat in the air is moved out of or into the home.
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