F.23
FAULT CODE
Vaillant
Temperature Spread Too High
Medium Severity
Engineer Required
The temperature difference between the flow and return water is too large. This usually indicates poor water circulation caused by a partially blocked pump or scaled heat exchanger.
Step-by-Step Fix Guide
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Step 1
Check system pressure is correct
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Step 2
Bleed radiators to release trapped air
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Step 3 Engineer only
If fault persists, a Gas Safe engineer may need to check the pump speed settings or carry out a powerflush
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.