Medium
D.75 on Vaillant Combi Compact 242EB

Your boiler is taking too long to heat up your hot water cylinder, causing it to stop the process for safety.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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

Maximum charging time for a storage without own controller

DIY fix possible

Check that the isolation valves on the pipework leading to your hot water cylinder are fully open.Ensure your cylinder thermostat is not set to an unusually high temperature.Reset the boiler to see if the error clears and monitoring returns to normal.

Find a Gas Safe engineer
Search the official register →

Related fault codes

F.20View →F.24View →D.71View →

Related guides you might find useful

No hot water but heating works

Almost always a stuck diverter valve on combis.

Read →

Banging / kettling / whistling noise

Each noise points to a different fault.

Read →

Boiler won't turn on — 9-step checklist

Work through these before the call-out.

Read →