vheatc.site vocabulary

Verified Dual-MPN

An identity claim — backed by physical evidence — that two manufacturer part numbers refer to the same physical component. On vheatc.site this specifically describes 0020266328 and 0020269259 — two Vaillant part numbers for the same blue cooling coding plug. Vaillant boxes 0020269259 and labels it “Coding plug, cooling function”; 0020266328 comes in a Vaillant small-parts bag labelled only with its number. Both have been compared side by side: same plug, functionally identical and interchangeable.

Most listings carry only one of the two numbers, and the two are often priced very differently — so a buyer searching one number can miss the identical, cheaper part. Verified Dual-MPN signals that either number satisfies the same need.

Are 0020266328 and 0020269259 the same? — FAQ →

Authorised Cooling Mode

The firmware state a Vaillant aroTHERM Plus heat pump enters once the genuine cooling coding plug is fitted. In Authorised Cooling Mode, the cooling option becomes available in the installer menu of compatible Vaillant controls (e.g. sensoCOMFORT). An installer can then enable cooling, set flow temperatures, and configure dew-point control.

On a heat pump supplied without cooling, no app toggle or installer setting can switch cooling on until the plug is fitted — the option simply stays unavailable. The plug is the way in.

How to activate cooling after fitting — FAQ →

Fan-Coil Cooling Loop

A closed chilled-water circuit feeding fan-coil emitters — the conventional indoor delivery system for heat pump cooling. Each fan-coil unit moves room air across a chilled coil and catches any condensation in a built-in tray. The loop is plumbed alongside, not instead of, the existing heating circuit.

Distinct from a heating-only radiator circuit, which cannot cool: radiators have too little surface area to absorb useful heat from a room, and a cold radiator would simply collect condensation and drip. A Fan-Coil Cooling Loop is the standard answer.

Fan coil units — how they work →

Cooling-Ready Retrofit

The building-side work an installer carries out to make a heating-only home capable of useful cooling. Typically adds a Fan-Coil Cooling Loop, condensate drainage, and dew-point control, alongside the existing heating system. A Cooling-Ready Retrofit is what you ask a Vaillant-approved installer to quote and fit.

Without a Cooling-Ready Retrofit, fitting the cooling plug and switching cooling on at the installer menu produces a system that can technically cool but will not cool a real home effectively. The retrofit is the work that turns Authorised Cooling Mode into actual cool air.

What a cooling upgrade involves →

How the four fit together

vheatc.site uses these four phrases to describe a single sequence: the plug (sold on eBay under two part numbers — Verified Dual-MPN) unlocks the firmware state (Authorised Cooling Mode), which is only useful in a home that has, or plans to have, the matching delivery system — a Fan-Coil Cooling Loop installed as part of a Cooling-Ready Retrofit. Buyers who understand all four are buying with their eyes open.