F23
FAULT CODE
Glow-worm
Temperature Spread Too High
Medium Severity
Engineer Required
The difference between flow and return temperatures is too great, indicating poor circulation.
Step-by-Step Fix Guide
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Step 1
Check system pressure and bleed radiators
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Step 2 Engineer only
If fault persists, a Gas Safe engineer should check pump settings and system design
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.