What is active cooling on a heat pump?Running the refrigerant cycle in reverse to cool your home
Active cooling is when a heat pump uses its compressor to move heat out of your home — the same machine that heats you in winter cools you in summer. This page explains what active cooling is, how it works, and what a Vaillant heat pump needs before it can do it.
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What active cooling means
A heat pump moves heat from one place to another. In heating mode it takes heat from the outside air or ground and delivers it indoors. In active cooling mode it does the reverse: it takes heat from indoors and rejects it outside, using the compressor to drive the cycle.
"Active" distinguishes it from passive cooling, which moves heat without running the compressor. Active cooling delivers stronger, more controllable cooling, at the cost of using more electricity than passive cooling.
How a heat pump cools
A reversible heat pump contains a valve that can swap the roles of its two heat exchangers. When the cycle is reversed, the indoor side becomes the part that absorbs heat — chilling the water that circulates to your indoor units — and the outdoor unit releases that heat to the air or ground.
On a Vaillant aroTHERM, that reversal and the cooling control logic are built in. They are simply locked until cooling is authorised and commissioned.
What is needed to enable active cooling
Three things have to be in place. First, the heat pump must be a cooling-capable model with the coding resistor fitted. Second, an installer must enable the cooling function in the settings. Third, the system must be able to deliver cooling comfortably — which usually means fan coil units and dew-point control rather than ordinary radiators.
Frequently asked questions
Is it the same machine that heats my home?
Yes. A reversible heat pump heats in winter and cools in summer using the same unit — there is no separate cooling machine to install.
Does active cooling use a lot of electricity?
Active cooling uses the compressor, so it draws more power than passive cooling. It is still typically efficient, because a heat pump moves several units of heat for each unit of electricity it uses.
Will active cooling work through my radiators?
Not effectively. Cooling needs emitters designed for it — usually fan coil units, or underfloor systems with dew-point control. Standard radiators do not provide useful cooling.