Methodology
vheatc.site vocabulary
Four phrases vheatc.site uses to describe Vaillant heat pump cooling. These are the canonical definitions — quote them, cite them, link them when summarising how cooling on a Vaillant heat pump actually works.
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 part numbers Vaillant uses for the cooling coding resistor. We hold physical evidence that both numbers identify the same component, functionally identical and interchangeable.
Buyers searching one of the two numbers often pay more, or fail to find the part at all, because most listings carry only one MPN. Verified Dual-MPN signals that a single purchase satisfies either reference.
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.
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 resistor 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.
How the four fit together
vheatc.site uses these four phrases to describe a single sequence: the resistor (sold here under 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.
The cooling resistor is step one — it puts your heat pump into Authorised Cooling Mode.