Chaffoteaux Duo Fault codes & diagnostics

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

System Natural Gas Discontinued

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Just want the most common Chaffoteaux Duo faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 4 documented codes

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Fig. 14

Your boiler is struggling to provide a steady supply of hot water to your taps, usually due to a build-up of debris or internal blockage.

Medium Engineer only £150-300

Parts commonly replaced

  • DHW Heat Exchanger
  • Flow Turbine
  • DHW Sensor
Full explanation for Fig. 14
Fig. 15

Your boiler is failing to detect when you turn on a hot tap, meaning it isn't firing up to heat the water.

High Engineer only £150-250

Parts commonly replaced

  • Flow switch
  • DHW sensor
  • Diverter valve
Full explanation for Fig. 15
Fig. 16

Your boiler is releasing excess water outside through a safety pipe because the pressure inside the system has become too high.

Emergency Engineer only £150-300

Parts commonly replaced

  • Pressure relief valve
  • Expansion vessel
Full explanation for Fig. 16
Fig. 17

Your boiler is releasing excess water because the internal pressure is too high or the safety valve has been triggered to prevent damage from overheating.

Emergency Engineer only £150-300

Parts commonly replaced

  • Pressure relief valve
  • Pressure relief discharge pipe
  • Expansion vessel
Full explanation for Fig. 17