Chaffoteaux Celtic 24 HE Fault codes & diagnostics

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

Combi Natural Gas 24 kW 2006-2010 Discontinued

Replaced by: Chaffoteaux Britony HE

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3 Emergency 20 High 9 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 32 documented codes

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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.i

Your boiler is struggling to control the temperature of your hot water because an internal valve is sticking and not moving correctly.

Medium Engineer only £120-220

Parts commonly replaced

  • Water governor valve
  • Diaphragm kit
  • Diverter valve actuator
Full explanation for 5.i
5.ii

Your boiler is struggling to provide hot water because the incoming water flow from the mains is too weak or restricted.

Medium DIY-safe £60-120

What to check first

  1. Check that your main stopcock is fully open.
  2. Ensure any isolation valves under the boiler are in the open position.
  3. Check other taps in the house to see if your local water provider is experiencing low pressure.

Parts commonly replaced

  • Inlet water filter
  • Flow switch
  • Pressure sensor
Full explanation for 5.ii
5.iii

Your boiler is struggling to heat water correctly because a dirty filter is restricting the fresh water entering the unit.

Medium Engineer only £90-£160

Parts commonly replaced

  • Inlet water filter
  • Flow restrictor
  • Heat exchanger (descaling)
Full explanation for 5.iii
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
5.vi

Your boiler is failing to heat your water properly because the internal valves that control gas flow are not responding as they should.

High Engineer only £140-£280

Parts commonly replaced

  • Gas Valve
  • Solenoid Coil
  • Control PCB
Full explanation for 5.vi
5.vii

Your boiler is struggling to provide consistent hot water because a safety sensor is failing to stay in the correct position while the water is running.

High Engineer only £120-280

Parts commonly replaced

  • Air Pressure Switch
  • Venturi Tube
  • Fan Assembly

Related codes

Full explanation for 5.vii
5.viii

Your boiler is struggling to heat water because it is not receiving enough gas to reach the required temperature.

High Engineer only £100-250

Parts commonly replaced

  • Gas Valve
  • Gas Meter Regulator
  • Inlet Pipework

Related codes

Full explanation for 5.viii
Showing 11–20 of 32
6.i

Your boiler has stopped working because there isn't enough water moving through the system to safely light the burner.

High DIY-safe £80-250

What to check first

  1. Check the pressure gauge on the front of the boiler; it should be between 1 and 1.5 bar.
  2. If the pressure is too low, use the filling loop valves to top up the water level.
  3. Ensure all radiator valves and isolation valves under the boiler are fully open.

Parts commonly replaced

  • Circulation pump
  • Water pressure sensor
  • Flow switch
Full explanation for 6.i
6.ii

Your boiler has stopped working because the internal pump that moves water around is stuck, meaning the burner cannot safely light.

High Engineer only £180-350

Parts commonly replaced

  • Circulation Pump
  • Pump Capacitor
Full explanation for 6.ii
6.iii

Your boiler has shut down because it cannot detect any water or sufficient pressure to safely light the burner.

High DIY-safe £0-120

What to check first

  1. Check the pressure gauge on the front of the boiler; it should be between 1.0 and 1.5 bar.
  2. Locate the filling loop (usually a silver flexible hose) under the boiler.
  3. Slowly open the valve(s) to top up the pressure until it reaches 1.2 bar, then close them tightly.
  4. Reset the boiler to see if the fault clears.

Parts commonly replaced

  • Filling loop
  • Low water pressure switch
  • Expansion vessel

Related codes

Full explanation for 6.iii
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
6.v

Your boiler is unable to provide central heating because its internal temperature sensor for the radiators has likely stopped working.

Medium Engineer only £90-160

Parts commonly replaced

  • Central Heating NTC Sensor
  • Thermistor
  • Wiring harness connectors

Related codes

Full explanation for 6.v
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.ii

Your boiler is releasing excess water because it is under too much pressure and hasn't been properly disconnected from the main water supply.

Emergency Engineer only £120-280

Parts commonly replaced

  • Pressure Relief Valve (PRV)
  • Expansion Vessel
  • Filling Loop Valve

Related codes

Full explanation for 7.ii
7.iii

Your boiler is releasing water through a safety pipe because internal pressure has built up too high, likely due to an internal air cushion failing.

Emergency Engineer only £120-250

Parts commonly replaced

  • Expansion Vessel
  • Pressure Relief Valve
  • Schrader Valve

Related codes

Full explanation for 7.iii
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
8.i

Your boiler is struggling to move water because there is air trapped inside the pipework or the pump.

Medium DIY-safe £80-220

What to check first

  1. Turn off the boiler and allow the radiators to cool.
  2. Use a radiator key to bleed all radiators in the house, starting from the ground floor.
  3. Check the boiler pressure gauge and top it up to between 1 and 1.5 bar if it has dropped.

Parts commonly replaced

  • Automatic Air Vent
  • Circulating Pump

Related codes

Full explanation for 8.i
Showing 21–30 of 32
8.ii

Your boiler's pump is struggling to move water because trapped air is stuck inside the system and cannot escape.

Medium DIY-safe £90-180

What to check first

  1. Locate the radiator bleed valve on your highest radiator
  2. Use a bleed key to release any trapped air until water appears
  3. Check the boiler pressure gauge and top it up to 1.5 bar using the filling loop if it has dropped

Parts commonly replaced

  • Automatic Air Vent (AAV)
  • Circulating Pump

Related codes

Full explanation for 8.ii
8.iii

Your boiler's internal pump is struggling to circulate water because small pieces of dirt or grit have become trapped inside it.

Medium Engineer only £120-£280

Parts commonly replaced

  • Circulating Pump
  • Central Heating Filter

Related codes

Full explanation for 8.iii
8.iv

Your boiler is struggling to circulate water because a internal filter is clogged, which is causing the pump to make an unusual noise.

High Engineer only £120-220

Parts commonly replaced

  • Central heating return filter
  • Circulating pump

Related codes

Full explanation for 8.iv
9.i

Your boiler is heating up too quickly because the water cannot circulate properly, likely due to a build-up of debris in its internal filter.

High Engineer only £90-180

Parts commonly replaced

  • Central heating return filter
  • Circulation pump
  • Heat exchanger

Related codes

Full explanation for 9.i
9.ii

Your boiler is overheating because water is not moving through the system quickly enough to carry the heat away.

High Engineer only £180-450

Parts commonly replaced

  • Circulation Pump
  • Main Heat Exchanger
  • Diverter Valve
Full explanation for 9.ii
9.iii

Your boiler is heating up too quickly because it is burning too much gas at once, causing it to shut down for safety.

High Engineer only £120-250

Parts commonly replaced

  • Gas Valve
  • Main Heat Exchanger
  • NTC Temperature Sensor

Related codes

Full explanation for 9.iii
10.i

Your boiler is struggling to push water through the pipes quickly enough, causing it to switch on and off repeatedly to avoid overheating.

High DIY-safe £90-250

What to check first

  1. Check that all radiator valves are fully open
  2. Inspect the boiler pressure gauge and top up to 1.5 bar if it is low
  3. Check for any visible leaks around radiators or pipework

Parts commonly replaced

  • Central heating pump
  • Main heat exchanger (de-scaling)
  • Flow temperature sensor
Full explanation for 10.i
10.ii

Your boiler is rapidly turning itself on and off because a safety sensor thinks it is overheating, preventing it from heating your home properly.

High Engineer only £120-220

Parts commonly replaced

  • Limit Stat (High Limit Thermostat)
  • Overheat Sensor
  • NTC Thermistor

Related codes

Full explanation for 10.ii
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
Showing 31–32 of 32
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