High
F28 on Glow-worm Ultracom 2 18sxi

Your boiler is trying to start up, but it cannot get the flame to light, which usually means there is a temporary issue with your gas or ignition.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

What the manual says

Manufacturer manual

The burner fails to ignite, initially, this may be due to air in the gas supply line.

From this model's manual
Verified against the Glow Worm/Glow Worm Ultracom2 12sxi installation & service manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Related fault codes

F29View →F54View →

All 35 fault codes on the Ultracom 2 18sxi

Seeing a different code? Every code this model can display, in one place.

ErrF00F01F10F11F20F22F23F24F26F27F29F32F49F61F62F63F64F65F67F68F70F71F72F73F74F76F77F83F84F85F86S.96S.98

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