BoilerFaultCodesGlow-worm S.54 Fault Code
Also written as S54 — same fault.
The Glow-worm S.54 fault code means: your boiler has sensed that heat is rising too quickly because there isn't enough water moving through the system to carry the heat away.. It appears on 30 Glow-worm models in our database.
Technical description: waiting time: no water in system, temperature (gradient error) rise flow / return sensor too high
What causes the Glow-worm S.54 fault?
This fault occurs when the boiler detects a sudden, rapid spike in temperature because there is no water flow to carry the heat toward your radiators. The most common reasons are a seized internal pump, an air lock in the pipework, or a blockage that is preventing the water from circulating through the heat exchanger. Essentially, the boiler is protecting itself from overheating by shutting down when it senses the water is standing still.
This issue often surfaces in autumn when the heating is turned on for the first time after summer, as pump components can seize up during long periods of inactivity.
DIY fix possible
Check the pressure gauge on the front of the boiler or under the casing.If the pressure is below 1.0 bar, use the filling loop handles to top up the system to 1.5 bar.Ensure all radiator valves are fully open to allow water to flow.Reset the boiler using the power button or reset switch.
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Glow-worm models that show the S.54 fault code
Click a model for the full fault code list and model-specific repair notes.
- 30cxi Repair: £90-180
- 38cxi Repair: £90-200
- Betacom4 Repair: £80-150
- Easicom 24 Repair: £90-£180
- Easicom3 Combi Repair: £80-150
- Easicom3 System Repair: £80-150
- Energy Repair: £0-£120
- Energy Regular Repair: £100-250
- Energy System Repair: £80-150
- Energy7 Combi Repair: £120-250
- Energy7 Regular Repair: £100-200
- Energy7 System Repair: £90-180
- Essential Repair: £80-150
- Flexicom 18sx Repair: £80-250
- Flexicom 24c / 28c Repair: £80-150
- Flexicom cx Repair: £80-220
- Flexicom hx Repair: £80-250
- Flexicom sx Repair: £80-250
- Sustain 12s Repair: £90-180
- Ultimate 3 25R Repair: £120-250
- Ultimate3 Combi Repair: £90-250
- Ultimate3 System Repair: £80-150
- Ultracom 2 CXI Repair: £100-280
- Ultracom 2 HXI Repair: £100-280
- Ultracom 2 SXI Repair: £100-280
- Ultracom 24cx 30cx Repair: £100-280
- Ultracom 35 Store Repair: £100-280
- Ultracom cxi Repair: £100-280
- Ultracom hxi Repair: £80-150
- Ultracom sxi Repair: £100-280
Source
Glow-worm S.54 fault code information on this page is sourced and cross-checked against the official Glow-worm service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026