How to Enable Cooling Mode on a Vaillant aroTHERM Heat Pump

Step 1 — Confirm the heat pump and system are ready

Before any work begins, a Vaillant-approved installer should confirm two things. The first is that your aroTHERM is a cooling-capable model — check the model code on the data plate and, where possible, the installer manual’s cooling section. The cooling plug is listed for the aroTHERM Plus range, VWL 35/6 to VWL 125/6.

The second is that the heating system can actually deliver cooling. Cooling works through emitters designed for it — typically fan coil units, or underfloor circuits with dew-point control. Ordinary radiators do not provide useful cooling and can cause condensation, so confirm the emitter strategy with your installer first.

Step 2 — The installer fits the cooling plug

The cooling coding plug — Vaillant 0020269259, boxed and labelled “Coding plug, cooling function”, or the identical 0020266328 — plugs into a defined coding position in the heat pump wiring. This is the physical token that authorises cooling.

This is a competent-installer task. It involves working safely inside the unit with the power isolated. With the plug fitted, the controller can recognise that cooling is permitted — but cooling is still not switched on.

Step 3 — The installer enables cooling in the installer menu

With the plug in place, the installer goes into the installer level of the system control (such as sensoCOMFORT) and enables the cooling function. On a unit supplied without cooling, the option only becomes available once the plug is detected.

The installer then configures cooling behaviour — for example the minimum cooling flow temperature and dew-point settings — so the system cools without creating condensation. The exact options depend on your control and system.

Step 4 — Commissioning and handover

Finally the installer commissions cooling: testing that the heat pump reverses its cycle correctly, that the cooling emitters respond, and that any rooms that should not be cooled are isolated as intended. After a successful test, you should be shown how to switch between heating and cooling on your control.

Frequently asked questions