What is active cooling on a heat pump?

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.

On a Vaillant aroTHERM Plus, that reversal and the cooling control logic are built in. On units supplied without cooling, 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 cooling plug fitted where it is needed. 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, or underfloor heating with dew-point control, rather than ordinary radiators.

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