This refers to the type of electrical supply that the heat pump needs.
Most properties in the UK have a stamdard 100A single phase power supply (ie a live and neutral wire) .
Some larger properties or commercial properties in the UK may have a 3-phase power supply
Smaller heat pumps are normally single phase and 3-phase is generally used for larger models, Single phase heat pumps are available up to around 35kw. Over this all heat pumps will be 3-phase models
Single phase power is 220v to 240v and uses one live wire and one neutral wire.
3-Phase power supplies are 380v to 415v and use three live wires (and sometimes also a neutral wire)
If you are not sure what electrical supply you have, ask your electrician to check this before ordering your heat pump.
3-Phase power is more common in mainland Europe eg Portugal, France and Spain than in the UK and is fitted as standard to most new properties in some parts of mainland Europe.
As a guide, for larger heat pumps (eg over 24kw), then if 3-phase power is available in the pool room, it is better to use a 3-phase pool heat pump.
If in doubt, please call us for more advice.