Vaillant flexoTHERM Cooling: Do You Need the Cooling Plug?

The short answer

Check before you buy. The cooling plug is listed for the aroTHERM Plus range. On a ground-source heat pump, how cooling is provided depends on the heat source and the accessories fitted, so the right part — if any — is found in your unit’s installer manual or confirmed by a Vaillant-approved installer.

Active and passive cooling on ground source

Vaillant’s documentation for its ground-source range describes both active cooling, where the compressor runs to chill the water, and passive cooling, where heat is moved into the ground loop without running the compressor for cooling. Which applies depends on how the heat source is arranged.

Vaillant also describes a passive cooling module for ground-source systems with a collector or borehole. Passive cooling is very cheap to run but gentler than active cooling.

Radiators are not an option for cooling

Vaillant’s flexoTHERM operating instructions state that cooling mode with radiator heating systems is not permitted, because radiators do not offer enough heat-transfer area. As with any heat pump, cooling needs fan coil units or underfloor heating with dew-point control.

What to check before buying anything

Note the full model code from the data plate (ground-source units use VWF codes), find the cooling section of your installer manual, and check which heat source your system uses. Then ask a Vaillant-approved installer how cooling is enabled on your unit.

If your manual or installer does call for the cooling coding plug, it is sold on eBay as 0020269259 (boxed) and as the identical 0020266328.

Frequently asked questions