Which Vaillant heat pumps need a cooling resistor?The aroTHERM and VWL families that the coding plug applies to
The Vaillant cooling resistor authorises cooling mode on cooling-capable Vaillant heat pumps in the aroTHERM and VWL families. This page covers which families it applies to and how to confirm your own unit — but the only reliable check is your model number and a Vaillant-approved installer, because production has varied over the years.
Updated
The families it applies to
The cooling resistor is relevant to Vaillant air-source heat pumps in the aroTHERM range, sold under VWL model codes, and to flexoTHERM and flexoCOMPACT ground-source units sold under VWF model codes. These are the families Vaillant builds as reversible — physically able to run their refrigerant cycle in reverse to provide cooling.
Within those families, whether your specific unit needs the resistor, and whether the resistor is the right enabler for it, depends on the model and production year. Always confirm with a Vaillant-approved installer before ordering.
aroTHERM Plus and aroTHERM Split
The aroTHERM Plus is Vaillant’s current monobloc air-source heat pump, sold under VWL ../6 series codes. Vaillant presents it as a heating, hot-water and cooling platform — the cooling capability is built in, and is enabled rather than added.
The aroTHERM Split keeps the compressor outdoors and connects to an indoor hydraulic station, sold under VWL ../5 AS S2 series codes. Per Vaillant documentation, S2 units are designed so cooling can be activated later with an optional accessory.
Legacy aroTHERM and flexoTHERM / flexoCOMPACT
Earlier aroTHERM units, sold under VWL ../5 AS series codes, are also part of the air-source family. Because production details have changed over time, it is especially important to verify a legacy unit against its model and serial number before ordering any part.
flexoTHERM and flexoCOMPACT ground-source heat pumps, sold under VWF codes, support cooling too, but the picture is more conditional — active and passive cooling depend on the heat source arrangement, and Vaillant’s manuals place real limits on cooling with a ground heat source. Check your installer manual.
- Air-source heat pumps use VWL model codes.
- Ground-source heat pumps use VWF model codes.
- The model and serial number are on the unit’s data plate.
A family-level overview. This is a guide, not a guarantee — confirm your exact model with a Vaillant-approved installer before ordering.
| Family | Models | Notes |
|---|---|---|
| aroTHERM Plus | Monobloc air-source, VWL ../6 series | Current range; presented by Vaillant as a heating, hot-water and cooling platform. |
| aroTHERM Split | VWL ../5 AS S2 series | Compressor outdoors, indoor hydraulic station; cooling activated later with an optional accessory. |
| Legacy aroTHERM | VWL ../5 AS series | Earlier air-source units; verify model and serial number before ordering. |
| flexoTHERM / flexoCOMPACT | VWF series | Ground-source; active and passive cooling depend on the heat source — check the installer manual. |
Frequently asked questions
How do I know if my model needs the resistor?
Find your model number on the unit’s data plate — it begins with VWL for air-source or VWF for ground-source. Then ask a Vaillant-approved installer to confirm whether your specific unit needs the coding resistor to enable cooling.
Does both aroTHERM Plus and aroTHERM Split use it?
Both families are cooling-capable. The aroTHERM Plus is the current monobloc range; aroTHERM Split (S2 series) is designed so cooling can be activated later. Confirm the exact enabler for your unit with an installer.
What about an older aroTHERM?
Legacy aroTHERM units (VWL ../5 AS) are part of the air-source family, but production details have changed over the years. Verify the model and serial number before ordering any part.
Do flexoTHERM ground-source units need it?
flexoTHERM and flexoCOMPACT support cooling, but whether active or passive cooling applies depends on the heat source arrangement. Check your installer manual and confirm with a Vaillant-approved installer.
Is the part the same regardless of family?
The cooling resistor is supplied under part numbers 0020266328 and 0020269259, which are functionally identical and interchangeable. Compatibility still depends on your specific model — confirm before ordering.