Air Source Heat Pump Installation

The parts of an air source heat pump system, in plain English

• Outdoor unit: the box outside with a fan in it. It pulls heat out of the air, even cold air, the way a fridge pulls heat out of its inside, just in reverse.
• Refrigerant circuit: the sealed loop inside the outdoor unit that carries the heat from the air into your heating water. It's why a heat pump can give out three or four units of heat for one unit of electricity.
• Hot water cylinder: a heat pump heats water more slowly than a combi, so it stores it in a cylinder. Every install includes one unless you already have a suitable cylinder.
• Buffer tank or volumiser: a small tank that gives the system some water to work with so it runs smoothly. Fitted where the design needs it.
• Controls: the heat pump controller and room thermostats. Set up for weather compensation, which adjusts the water temperature to the weather outside so the system runs as cool as it can.
• Radiators: heat pumps run cooler than boilers, so radiators need to be big enough. Some homes keep them all, some need two or three upsized.
• Underfloor heating: the ideal partner for a heat pump, because it runs at low temperature all day.
• Electrical supply: a dedicated supply to the outdoor unit, which is why we're NICEIC registered as well as MCS.
• MCS certificate: issued at commissioning. It proves the system was designed and installed to the standard, and it's what releases the grant.
• Boiler Upgrade Scheme grant: £7,500 for gas homes, £9,000 for oil or LPG, taken off your quote.

What's involved in the installation

• Survey and design: every room measured, heat loss calculated, the heat pump sized, the cylinder and outdoor unit positions agreed, radiators checked. Under an hour on site, then the design is done back at the desk.
• Application: the grant application goes in before the work starts and you confirm it by email.
• Day one: outdoor unit fitted on a wall bracket or a ground stand, pipework and electrical supply run to it, old boiler removed.
• Day two and three: cylinder, buffer and controls installed, radiators changed where needed, system filled and pressure tested.
• Commissioning: the system run up, weather compensation set, hot water schedule set, everything tested and the MCS certificate issued. Two to four days in total for most homes.

Honest advice: what's overkill

• An oversized heat pump: bigger is not safer. An oversized heat pump cycles on and off, wears faster and costs more to run. Size to the heat loss calculation, not to nerves.
• Replacing every radiator: only the ones the calculation says. Many homes need two or three changed, not all of them.
• A heat pump in a house that leaks heat: if the survey shows the house needs a 16kW heat pump, the cheaper answer is insulation first, then a smaller heat pump. We'll say so.
• Keeping the boiler as a backup: the grant requires it to come out, and a well designed heat pump doesn't need one. If you'd rather keep gas for now, a new boiler is the honest answer.
• Worth paying for: the survey and heat loss calculation. It's free with us, and it's the difference between a heat pump that keeps the house warm at low cost and one that doesn't.

When to ask for a survey

If the boiler is over ten years old, or you're planning any heating work, get the survey before you spend on gas. Send your postcode and a photo of the boiler. Book a free survey