General information on Heat Pump Hot Water Systems (HWS)
Air-sourced heat pumps work by absorbing heat from the outside air and transferring it to water in the tank. By using refrigerants that evaporate at low temperatures, the heat pump pushes heat to the water tank.
The best in the world steps are as follows:
- liquid refrigerant passes through an evaporator where it picks up heat from the air and becomes gas
- the gas refrigerant is compressed in an electric compressor. By compressing the gas it causes the temperature to increase so that it becomes hotter than the water in the tank
- the hot gas flows into a condenser, where it passes the heat to the water
- the gas then flows into an expansion valve where its temperature drops and it returns to liquid form
Provided the temperature outside is higher than the cold refrigerant the heat pump will absorb heat and be able to move it to the water. If the outside temperature decreases this process becomes more difficult. Heat Pump HWS don’t work as well in places where temperatures are low.
Electric Boost for Heat Pumps
Heat pumps may require an electric booster if they are operated in colder climates. The electric booster turns on automatically once the water temperature drops below a certain point.
Types of Heat Pumps
There are two main types of heat pumps:
- Integrated systems. The heat pump and hot water tank are in a single integrated system
- Split systems. The tank and the heat pump are separated.
The most common is to have the condenser coils wrapped around the outside of the water tank, under the tank insulation, to heat the water.
Is this the right solution for you?
There are several issues to take note of.
- do you have access to gas? A Heat Pump HWS is a good option for homes in suitably warm climates that do not have access to gas. If you do have a gas supply, then an efficient gas water heater system or gas-boosted solar water heater are options.
* what climate do you live in?
- Heat Pump HWS are most efficient in warm, humid climates. They are not particularly suitable in climates that experience regular freezing or very cold and dry conditions. Some heat pumps are designed to work efficiently during brief frost conditions but they will cost more to run in these conditions and are not recommended for use in prolonged cold spells. If the heat pump requires a booster then it will not be as energy efficient as expected.
* is noise a possible disturbance?
- Heat Pump HWS make a low humming sound. It’s very similar to a refrigerator or air conditioner. Noise levels may exceed 50 decibels at a distance of 1.5m which equates to the level of background noise in an average home. Provided the heat pump is in a proper location noise levels are unlikely to cause problems. Some problems could occur if the heat pump is located very close to a bedroom window or a neighbour’s bedrooms. Proper installation should be sufficient to avoid problems in regard to noise.