How heat pump water heaters work
Heat pump hot water systems operate on the same principle as your refrigerator, but in reverse. They take ambient heat from the air and transfer it to an extremely cold liquid refrigerant, which is fed around in copper tubing. The liquid is then pulled back into a compressor where it is compressed. As the pressure rises, the temperature increases. From here it travels to the condenser, where the heat from the refrigerant is transferred to the water in the tank. The expansion valve then reduces the pressure and restarts the cycle.
Types of heat pump hot water system
Apart from the way in which they heat water, heat pump systems operate in the same way as standard storage tank systems. Heat pumps run on electricity, so natural gas versions are not available.
Where are heat pump hot water systems most commonly found?
The recent phase out of electric hot water systems has meant that heat pump systems are becoming more popular in Australia. They are easily adaptable to fit the same space as the electric storage tank systems they often replace. Heat pumps do not require gas reticulation or roof collectors as gas and solar hot water systems do. Heat pumps work much better in warmer climates where they can gather more heat from the air.
Is a heat pump system for me?
Heat pump hot water systems use approximately two thirds less electricity than a standard electric storage tank. This has to be weighed against whether the tank it is replacing used off-peak electricity rates, though. Heat pumps operate whenever they are required, and will often run during peak electricity tariff times. The added cost of using electricity at peak times may well negate the savings made by using less electricity overall, so if you are considering a heat pump hot water system you will need to carefully consider the running costs.
Because of the way the heat is absorbed from the air, heat pump systems generally work best where the ambient temperature is consistently greater than about 19ºC. While heat pump hot water systems will work in cooler climates, the compressors will need to work harder and may not last as long, adding to cost on two different fronts.
Heat pump systems come into their own in areas where solar collectors are not a desirable or viable option, and where gas is not available.
Heat pump systems are easy to install. Requirements for installation are similar to those for traditional electric storage tank hot water systems, although heat pumps will also generate quite a bit of noise (about the same as a medium sized air conditioner or a refrigerator). When choosing a location for your system, you should be mindful of how close the unit will be to neighbours’ windows and doors, and of your state’s noise control regulations. Certain models of heat pump will perform better than others in this regard, and some manufacturers will also advise you of a decibel range (dBA).
Because heat pumps also take air in, you should ensure that the vents are not located near any corrosive chemicals, as these can be sucked into the system and corrode it from inside.