How to activate cooling on a Vaillant aroTHERM heat pumpA two-part job: fit the coding resistor, then enable cooling in the menu
Activating cooling on a Vaillant aroTHERM heat pump is not a single switch. It is a two-part job carried out by a Vaillant-approved installer: first the cooling coding resistor is fitted, then the cooling function is enabled in the installer menu. The heating system itself also has to be suitable for cooling. This guide walks through the steps in order so you know what to expect.
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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 designation on the data plate and, where possible, the installer manual’s cooling section.
The second is that the heating system can actually deliver cooling. Per Vaillant documentation, 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 coding resistor
The cooling coding resistor — Vaillant part 0020266328, also supplied as the interchangeable 0020269259 — plugs into a defined coding-plug 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, so we strongly recommend it is carried out by a Vaillant-approved installer. With the resistor 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 resistor in place, the installer enters the installer menu on the system control (such as sensoCOMFORT) and enables the cooling function. Only once the resistor is detected does the cooling option become available to select.
The installer then configures cooling behaviour — for example minimum cooling flow temperature and dew-point settings — so the system cools without creating condensation. Confirm these settings with your installer; 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 non-cooled rooms are isolated as intended. After a successful test, you should be shown how to switch between heating and cooling on your control.
The job at a glance — what happens, and who does it.
| Stage | What it involves | Who does it |
|---|---|---|
| Check suitability | Confirm cooling-capable model and suitable emitters | Vaillant-approved installer |
| Fit coding resistor | Plug the resistor into the coding-plug position | Vaillant-approved installer |
| Enable in menu | Switch on the cooling function in the installer menu | Vaillant-approved installer |
| Commission | Test cooling operation and hand over controls | Vaillant-approved installer |
Frequently asked questions
Is fitting the resistor enough to get cooling?
No. The resistor authorises cooling, but an installer must still enable the cooling function in the installer menu and commission it. Both parts of the job are needed.
Can I activate cooling myself?
We strongly recommend a Vaillant-approved installer carries out both fitting and activation. It keeps the work within warranty terms and ensures cooling is set up safely, including dew-point protection.
Will cooling work through my existing radiators?
Not effectively. Per Vaillant documentation, cooling needs emitters designed for it — usually fan coil units. Standard radiators give little useful cooling and risk condensation.
Does every aroTHERM support cooling?
Cooling is a model-dependent option. Check your model designation and installer manual, or confirm with a Vaillant-approved installer before ordering the resistor.
How long does activation take?
Fitting the resistor and enabling cooling is usually a short visit. Most of the work and cost is in making sure the emitters and controls are suitable — confirm scope with your installer.