Glow-worm F.24 Fault Code: Temperature Rise Too Fast
Hertfordshire, Bedfordshire & Cambridgeshire
F.24 on a Glow-worm is a safety switch-off because the temperature rose too quickly.
Another circulation fault, and closely related to F.23. Water that is not moving heats up very fast.
What F.24 actually means
The boiler watches how quickly the water temperature climbs. On a system with proper flow, heat is carried away and the rise is gradual.
A very rapid rise means the heat has nowhere to go, so the boiler stops before it overheats.
What you can safely check yourself
Do not keep resetting it. It is protecting the heat exchanger.
Check system pressure is in the normal range.
Check that radiator and isolation valves are open.
Bleed the radiators if there is any chance of air in the system.
When to stop, and why
If pressure and valves check out and it still trips, call an engineer.
What causes it beyond the simple checks
A seized or failing pump, an air lock, a closed valve, sludge restricting the heat exchanger, or a pump running too slowly for the system. Glow-worm is part of the Vaillant Group and the Energy range shares its fault code structure with Vaillant appliances.
How Vantage can help
We are Gas Safe registered under 956889 and cover Hertfordshire, Bedfordshire and Cambridgeshire, with an emergency line answered 24 hours a day. Call us on 01462 506374. See also boiler repair and boiler servicing.
Frequently asked questions
What is the difference between F.24 and F.20?
F.24 is about how fast the temperature climbs, F.20 is about it reaching the overheat limit. They usually have the same underlying cause.
Is F.24 serious?
The switch-off is protective. The cause needs finding before it damages the heat exchanger.
Could it just be the pump setting?
Sometimes. A pump set too low for the system will do it, and that is a quick fix.
Related fault codes
Other Glow-worm codes: F.20 · F.22 · F.23 · F.25 · F.27 · F.28 · F.29 · F.32 · F.61 · F.75 · all boiler advice. See also boiler repair. See also power flushing.
In Glow-worm’s own words
The Glow-worm Energy range fault finding table lists F.24 as: Safety switch-off. Temperature rise too fast
Glow-worm use different code sets across their ranges and generations. The definition above comes from The Glow-worm Energy range fault finding table. If your boiler is a different model and the code behaves differently, check the manual for your appliance or ring us and we will tell you what it means on your unit.
When to call an engineer
If the checks above have not cleared it, the next steps are engineer work and the boiler should not be reset repeatedly in the meantime. Call Vantage Plumbing and Heating on 01462 506374. We are Gas Safe registered under 956889, the line is answered by a person at any hour of any day, and you get a price before anyone starts.
Need help today?
Call and speak to a person, any hour, any day of the year. Get a fixed price quote or call 01462 506374.
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