Chaffoteaux Celtic 24 HE Fault codes & diagnostics

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

Combi Natural Gas 24 kW 2006-2010 Discontinued
GC Number 47-980-01

Replaced by: Chaffoteaux Britony HE

Download the Chaffoteaux Celtic 24 HE manual The official installation & service manual (PDF) — the exact document these fault codes were verified against. PDF

The fault code is already on your display

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

Severity at a glance

Each cell = one fault code. Hover to identify.
1 Emergency 8 High 2 Medium
Just want the most common Chaffoteaux Celtic 24 HE faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 11 documented codes

Tap any card for details

2a

Your boiler is making a loud noise because the water pressure inside the system is too low for it to run properly.

High DIY-safe £60-120

What to check first

  1. Locate the filling loop (the flexible silver hose usually underneath the boiler).
  2. Slowly open the valve(s) until you hear water entering the system.
  3. Watch the pressure gauge and close the valves when it reaches 1.5 bar.

Parts commonly replaced

  • Filling loop valve
  • Expansion vessel service
  • Automatic air vent

Related codes

Full explanation for 2a
2b

Your boiler is making a loud noise because the internal pump that moves water around has stopped working.

High Engineer only £220-£450

Parts commonly replaced

  • Circulation Pump
  • Pump Capacitor
  • Main PCB

Related codes

Full explanation for 2b
5.iv

Your boiler is struggling to heat your water at the correct temperature because an internal component responsible for controlling air flow is the wrong type for this specific model.

High Engineer only £90-180

Parts commonly replaced

  • Air Venturi
  • Fan assembly seals

Related codes

Full explanation for 5.iv
5.v

Your boiler is struggling to control the temperature of your hot water because a safety sensor has become inaccurate.

Medium Engineer only £90-160

Parts commonly replaced

  • DHW limit thermostat
  • Hot water thermistor (NTC sensor)

Related codes

Full explanation for 5.v
6.iv

Your boiler is failing to light the flame because it cannot detect that water is moving through the system properly.

High Engineer only £120-280

Parts commonly replaced

  • Flow switch
  • Pump
  • Diverter valve diaphragm

Related codes

Full explanation for 6.iv
7.i

Your boiler has built up too much water pressure, causing it to leak water from the safety pipe to protect the system.

High DIY-safe £100-280

What to check first

  1. Check that the filling loop valves are fully closed and not letting in water.
  2. Bled water from a radiator through the air vent to reduce system pressure.
  3. Monitor the pressure gauge to ensure it stays between 1.0 and 1.5 bar when cold.
  4. If the pressure continues to rise on its own, call a Gas Safe engineer.

Parts commonly replaced

  • Expansion Vessel
  • Pressure Relief Valve (PRV)
  • Filling Loop
Full explanation for 7.i
7.iv

Your boiler is leaking internally between the heating and hot water systems, causing water to pour out of the safety pipe outside.

Emergency Engineer only £250-£450

Parts commonly replaced

  • Secondary Plate Heat Exchanger
  • Pressure Relief Valve (PRV)
  • Expansion Vessel recharge
Full explanation for 7.iv
10.iii

Your boiler is rapidly turning itself on and off because water is not flowing through the system correctly, causing it to overheat too quickly.

Medium DIY-safe £100-250

What to check first

  1. Ensure all radiator valves (TRVs) are fully open to allow water to circulate.
  2. Check that the central heating valves underneath the boiler are in the fully open position.
  3. Bleed all radiators to remove trapped air that could be blocking water flow.

Parts commonly replaced

  • Automatic bypass valve
  • Circulation pump
  • Primary heat exchanger (de-scaling)

Related codes

Full explanation for 10.iii
10.iv

Your boiler is overheating quickly and switching itself off because water cannot flow through the internal system properly.

High Engineer only £250-£650

Parts commonly replaced

  • Main Heat Exchanger
  • Secondary Plate Heat Exchanger

Related codes

Full explanation for 10.iv
12

Your boiler has lost water pressure, which prevents it from heating up or providing hot water.

High DIY-safe £80-250

What to check first

  1. Check for any visible leaks around radiators or pipes
  2. Locate the filling loop (usually two braided hoses) under the boiler
  3. Open the valves slowly until the pressure gauge is between 1.0 and 1.5 bar
  4. Close the valves tightly and restart the boiler

Parts commonly replaced

  • Diverter valve seal
  • Expansion vessel
  • Pressure relief valve
  • Automatic air vent
Full explanation for 12
13

Your boiler is gaining too much water pressure, which could eventually cause it to leak or shut down for safety.

High DIY-safe £90-280

What to check first

  1. Check that the external filling loop valves are tightly closed
  2. Disconnect the silver braid filling loop hose if it is safe and possible to do so
  3. Bleed a radiator to reduce the system pressure back to 1.5 bar
  4. Monitor the gauge; if pressure continues to rise with the loop disconnected, call an engineer

Parts commonly replaced

  • Filling loop valve
  • Plate-to-plate secondary heat exchanger

Related codes

Full explanation for 13