An air source heat pump (ASHP) system contains mechanical and electrical components that operate together to provide heating or cooling for a home.
All ASHP systems require an electrical connection and an electricity supply to function, but the specific requirements can vary depending on factors such as the type and size of system.
Standard air source heat pumps can typically require a 240-volt, 30-amp circuit to operate. Larger or more powerful systems may require a dedicated circuit with a higher amp rating. Circuit breakers and wire sizes may also be determined by the size and power of heat pump system.
Our own air source heat pump unit is served by a dedicated electrical power supply from inside our home with an isolation switch with circuit breaker located on the wall adjacent the unit.
In this article we provide more specific information on how air source heat pumps work and their electrical requirements, including what the electrical requirements for our own heat pump system are.
External air source heat pump units typically contain one or more fans, alongside a compressor, both of which require electricity in order to work. Any indoor apparatus may also require electrical supplies, such as air handling units and control systems.
Air source heat pumps consist of both internal and external components, each with their own electrical components.
Types of air source heat pump systems can include:
- Split-system ASHPs have an outdoor unit that contains the compressor and condenser and an indoor unit that contains the evaporator and air handler.
- Packaged ASHPs combine the compressor, condenser, and evaporator into one unit. Single-unit ASHPs are less common in homes but are often used in commercial applications.
- Air to air heat pumps, where the indoor apparatus consists of space heating equipment such as air handling units.
- Air to water heat pumps, where the indoor apparatus is made up of central heating equipment such as underfloor heating and radiators. Air to water heat pumps may also be used alongside a hot water tank to provide domestic hot water.
These systems can come in a variety of sizes and configurations depending on the needs of the building they’re installed in and the user.
The actual heat pump unit itself will sit outside a home and can contain a range of electrical components including (typical for the more commonly found split systems):
- One or more fans, used to force air through the unit to capture heat from the air.
- A compressor, used to help maximize the temperature gains from extracting heat from the air by increasing pressure of the refrigerant before transferring heat indoors.
Heat will be transferred indoors to the internal apparatus, the type of which can depend on the type of heat pump mentioned above (air to air or air to water).
For example, we have an 11.2kW air to water heat pump that works with both radiators and underfloor heating.
The electrical requirements for our internal apparatus can differ to that of an air to air heat pump system, which will use air handling units to provide heating or cooling.
This inside of our cupboard where all our main internal heating and hot water apparatus is located contains a range of electrical supplies.
All ASHP systems require an electrical connection to function, but the specific requirements vary depending on the type and size of the system you have.
The electrical requirements for our own heat pump are shown below.
Always follow the specific electrical requirements for your particular air source heat pump system and consult a qualified professional if unsure of the requirements.
Air source heat pumps require a dedicated circuit breaker to function properly. The circuit breaker’s size will depend on your heat pump’s current requirements. Regular ASHPs can require a 20-amp circuit breaker, while larger systems may require a 30- or 50-amp circuit breaker.
It’s important to ensure that a heat pump has the proper circuit breaker beforehand to avoid damaging the unit.
For example, the manual for our own heat pump states the following:
We therefore have a circuit breaker with isolation switch mounted on the wall next to our external heat pump unit.
As an example, our model of air source heat pump requires a circuit breaker capacity of 32A.
Many factors can affect a heat pump’s voltage requirements, including the system’s size, type of refrigerant, and efficiency rating.
A 240-volt, single-phase electrical supply is the most common voltage for ASHPs (or 230V for the UK). However, some larger systems may require a 208-volt, three-phase electrical supply.
If you live in an area with extreme temperatures, your heat pump may require a higher voltage to function properly.
Before running the equipment, you can check the voltage requirements for your heat pump in the manufacturer’s documentation. If your voltage is too low, your heat pump may overheat and become damaged. If your voltage is too high, it can create excess sparks that may lead to a fire.
Our air source heat pump has a power supply requirement of 230V 50Hz (single phase).
The electrical current requirements of your heat pump will depend on the size and type of system you have.
Most ASHPs can require between 15 and 20 amps of current. Larger systems may require up to 50 amps. Some heat pumps use a different type of refrigerant than others. Systems that use R-22 refrigerants may require more current than R-410A.
Our heat pump has a max rated current of 29.5A, with rated currents at different power inputs.
The gauge of wire you’ll need can depend on the size of your circuit breaker and the length of the wire run. For most ASHPs, you may need 10-gauge wire if your circuit breaker is 20 amps and 8-gauge wire if your circuit breaker is 30 or 50 amps.
The voltage drop and wire capacity may also be considered when determining the wire size. The voltage drop occurs when the electricity travels through the wire. It should not exceed 3% for heat pumps that use R-410A refrigerant and 5% for heat pumps that use R-22 refrigerant.
Exceeding the voltage drop can cause your heat pump to overheat and damage.
The manual for our own heat pump explains the following: