Home Heating 18 August 2020

How Does a Heat Pump Work?

Have you ever sat in the warm comfort of your home and wondered ‘exactly how does my Heat Pump work?’

Well, we’re glad you asked.

In heating mode, Heat Pumps are like a reverse refrigerator. That’s because they don’t create heat – they simply transfer it from one place to another.

So in winter the system absorbs heat from the cold air outside and transfers it inside your home using refrigerant as the heat transfer medium. It may seem counter-intuitive to use cold air as a heat source, but heat energy is present even at very cold temperatures.

In summer, the process is reversed and the pump will act as an air conditioner, extracting heat energy from the surrounding environment within your home and transferring it outside using the same heat transfer medium.

Reverse cycle or split-system?

Reverse cycle split system Heat Pumps consist of two components – an outdoor unit and an indoor unit. The outdoor unit contains the compressor, while the indoor unit contains the condenser and evaporator components of the system. The outdoor and indoor units are connected together by piping that carries the refrigerant needed to heat (or cool) the outside air.

With a split-system air conditioner, the compressor sits outside the home in a box that rejects the heat during cooling and absorbs heat on heating. The indoor unit component of the system distributes the conditioned air into the room that houses that unit.

A Heat Pump in heating mode operates just like it does in cooling mode, except that the flow of refrigerant is reversed by the aptly named reversing valve. This flow reversal means that the heating source becomes the outside air (even when outdoor temperatures are low) and the heat energy is released inside the home. The outside coil now has the function of an evaporator, and the indoor coil now has the role of the condenser.

Where does a Heat Pump heat?

One of the most important things to understand about Heat Pump operation and the process of transferring heat is that heat energy naturally wants to move to areas with lower temperatures and less pressure. Heat Pumps rely on this physical property, putting heat in contact with cooler and lower pressure environments so that the heat can transfer naturally. This is fundamentally how a Heat Pump works.

Ducted Heat Pumps supply the conditioned air into every room in the house. This is through ducts connecting all of the rooms in your home to one central indoor unit, generally located in the roof space. With a typical ducted system, each vent or duct is capable of heating a room with an area of around 80m2.

In low temperatures, all Heat Pumps have to perform a “defrost cycle” to remove ice build-up on the outdoor coils. This can mean that the Heat Pump will temporarily stop operating for several minutes or may produce slightly cooler air.


Ok, so let’s get into what ‘Fixed Speed’ and ‘Inverter Control’ means….

Fixed Speed

A fixed speed system only has a single speed compressor motor that is either on or off – it switches off when the desired temperature is reached and switches on again when the temperature drops to a set level. With just the one speed that the system can run at, it takes longer to get to the desired temperature which in turn leads to a lot more power usage when compared to inverter driven systems.

Inverter driven

Inverter technology uses a variable speed compressor motor much like that of a car – it slows down and speeds up as needed to hold a selected comfort setting. This technology means the desired room temperature will be reached faster and maintained more efficiently.

Inverter technology also provides a more precise room temperature without the fluctuations and energy requirement of fixed speed systems. What’s more, the speed control of the outdoor unit also means quieter operation, which is especially important for you and your neighbours.

So there you have it. A Heat Pump is a truly amazing invention that is an integral and much valued addition to any Kiwi home – no matter the season.

And remember – when the weather turns, turn to someone you can trust. Rinnai – your specialists in home comfort.