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Heat, pulled out of cold air
There’s useful heat in outside air even on a frosty morning on the Knavesmire. A heat pump collects it, concentrates it and moves it into your heating and hot water. Here’s how, without the sales gloss.
The cycle, in four moves
A refrigerant goes round a sealed loop inside the outdoor unit, over and over. Your heating water never leaves the house side.
Flow temperature is where the money is
A gas boiler typically sends water round at 65 to 75°C. A heat pump is at its most efficient far lower than that, often somewhere in the 35 to 50°C range.
Every degree the system has to push the water up costs efficiency. So the aim of the design is to heat every room on the coldest expected day with the lowest flow temperature the house allows. That’s why radiator sizes come into it: a larger radiator gives out the same heat at a lower temperature.
It’s also why the controls matter. We set up weather compensation, which nudges the flow temperature up only as it gets colder outside, rather than running hot all winter just in case.
Will it cope with a York winter?
Yes, when it’s designed for one.
Heat pumps keep extracting heat from air well below freezing. They do get less efficient as it gets colder, which is exactly why a system is sized for the local winter design temperature rather than an average day.
On cold, damp mornings, the sort the Vale of York does well, you’ll sometimes see the unit steam for a few minutes. That’s a normal defrost: it briefly clears frost from the coil, and the meltwater runs off through the condensate drain. That’s why we lead it somewhere it won’t freeze across a path.
- Monobloc unitsEverything sealed in the outdoor box; only water pipes run into the house. That’s what nearly all of our installs are.
- Natural refrigerantThe Vaillant aroTHERM plus range runs on R290, a refrigerant with very low global warming impact.
- Quiet when sited properlyRoughly fridge-level at a few metres. Anti-vibration feet, and not under a bedroom window.
- Mostly VaillantMost systems we fit are Vaillant aroTHERM plus; we also fit Mitsubishi Ecodan where it suits the house.
What goes where
A heat pump system is more than the box in the garden.
More questions about how they work
Is a heat pump the same as air conditioning?
The machinery is related, but an air-to-water heat pump heats water for radiators, underfloor heating and your cylinder. Air-to-air units blow warm air into rooms instead and qualify for a much smaller grant. Everything on this site is air-to-water.
What does SCOP mean?
Seasonal coefficient of performance: roughly how many units of heat you get, averaged over a year, for each unit of electricity. A well-designed system running at a low flow temperature typically lands somewhere around three or above. The same heat pump fitted badly can do a lot worse.
Should I turn it off when I go out?
Usually no. Heat pumps work best ticking over steadily rather than recovering a cold house in a hurry. We set the controls up for how you live and show you which few settings are worth touching.
Can I keep my gas boiler as a back-up?
The Boiler Upgrade Scheme doesn’t fund hybrid systems, so to get the grant the heat pump replaces the boiler. A properly sized system doesn’t need a back-up boiler.
Want to know what your house would need?
A heat loss survey answers it. Ring and we’ll talk it through first.