109 High
Your boiler has detected that the water inside is not circulating properly or there is air trapped in the system, causing it to stop for safety.
Technical description: Clas net one / Clas one CombiClas system one
Typical repair cost: £100-£250 (including labour)
DIY fix possible
Check if your boiler pressure is between 1 and 1.5 bar on the gauge.Attempt to bleed any air from your radiators using a radiator key.Restart the boiler by pressing the Reset button to see if the fault clears.
Protect yourself from future repair bills
A boiler cover plan would cover faults like 109 — no call-out fees, no surprises.
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Parts commonly replaced
- Circulation Pump
- Automatic Air Vent
- Main Heat Exchanger (De-sludging)
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