Heatline S24 / S30 Fault codes & diagnostics

2 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.

Combi Natural Gas 24-30 kW Discontinued
Choose your boiler type

The S24 / S30 range comes in 2 types

Pick the one you have. The fault codes, GC numbers and manual differ by type.

S24 Compact 5 codes · 1 GC number S30 Compact 5 codes · 1 GC number
Each model has its own manual A family spans several manuals, one per model or generation. Pick your model above and its page has the manual its fault codes were read from.

The fault code is already on your display

Note it down before pressing reset — resetting clears the code immediately. How to read fault codes →

Fault codes

All 2 documented codes

Tap any card for details

Fault on DHW sensor

Your boiler is struggling to detect the temperature of the water coming out of your hot taps, which means it cannot heat your hot water correctly.

Medium Engineer only £120-200 Shared across the S24 / S30 range

Parts commonly replaced

  • DHW NTC thermistor sensor
  • Wiring harness
Full explanation for Fault on DHW sensor
Overheat Thermostat

Your boiler has switched itself off because it has become too hot internally and needs to be reset by a professional to ensure it is operating safely.

High Engineer only £120-250 Shared across the S24 / S30 range

Parts commonly replaced

  • Overheat thermostat
  • Central heating pump
  • PCB
Full explanation for Overheat Thermostat