S.53
FAULT CODE
Vaillant
Heat Demand Blocking (Anti-Cycle)
Low Severity
DIY Check Possible
The boiler has satisfied the heating demand and is in its anti-cycling period before it can restart. This is normal protective behaviour.
Step-by-Step Fix Guide
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Step 1
No action required — the boiler will restart automatically when needed
Gas Safe Reminder
Work on gas appliances must be carried out by a Gas Safe registered engineer. The steps above cover safe checks a homeowner can perform - any internal component replacement requires a qualified professional. If in doubt, always call an engineer.