What does the Glow-worm Ultimate F100 fault code mean?
The F100 fault code indicates a domestic hot water (DHW) temperature warning, suggesting that the water temperature is exceeding safe limits. This can lead to potential overheating issues within the boiler system.
Common Causes
- Thermostat Malfunction: A faulty thermostat may not accurately read the water temperature, causing the boiler to overheat.
- Blocked Heat Exchanger: A blockage in the heat exchanger can restrict water flow, leading to excessive temperature build-up.
Can I fix it myself? (DIY)
It is recommended to call a Gas Safe Engineer for this issue, as it involves gas and electrical components that require professional handling for safety reasons.
Estimated Repair Cost (2026 UK Prices)
The estimated repair cost for addressing the F100 fault could range around £150 to £300, primarily depending on whether the thermostat needs replacement or if the heat exchanger requires cleaning or repair.