Medium
d.27 on Vaillant Home System

Your boiler is confused about how it should be controlling an external part, such as a pump or valve, because the settings for its internal switch are incorrectly configured.

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

Technical description

Function of relay 1 (multi-functional module): 1=Circulation pump, 2=External pump, 3=Cylinder charging pump, 4=Extractor hood, 5=External solenoid valve, 6=External fault message, 7=Solar pump (omitted), 8=eBUS remote control, 9=Legionella protection pump, 10=Solar valve

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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