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Keston
Fault Codes
Listed below are the common Keston fault codes as described by the boiler manufacturer along with a possible cause.
C36 Combi Gas Boiler Error Codes
| Fault Code | Possible Cause |
|---|---|
| E01 | Ignition failure – the boiler has attempted to light 5 times and not succeeded – check the gas supply is on |
| E02 | False flame – possibly a problem with the power supply |
| E03 | Boiler overheat – check that any valves to the heating circuit have not been shut down, no air in the system and that the water pressure is correct |
| E05 | Fan failure – boiler cannot detect fan rotation – check fan operation and both connectors onto fan |
| E07 | Flue overheat – check combustion and flue temperature vs. return temperature – the flue temperature should be no more than 10C above return temperature. Possible heat exchanger fault. |
| E08 | Flame circuit error – possible control box fault |
| E09 | Valve drive error – possible gas valve or control box fault |
| E10 | Control box errors – possible faulty control box |
| E11 | The automatic test for calibration of flow and return sensors has failed – check both flow and return sensors are located on the correct pipes and are producing the correct readings |
| E12 to E22 | Control box errors – possible faulty control box |
| E23 | Water filling error – check water pressure sensor |
| E24 | Water pressure lost 4 times in 24 hours – possible leak, check system and boiler |
| E25 | Control box errors – possible faulty control box |
| E26 | Flame drop out – check for obstruction of the flue and/or air terminals, blockage/freezing of the drain pipe or a low gas supply (LPG). |
| E30 | Flow sensor short circuit – check connections to flow sensor |
| E31 | Flow sensor open circuit – check connections to flow sensor are in place |
| E32 | DHW sensor short circuit – check connections to domestic hot water (DHW) sensor |
| E33 | Domestic hot water (DHW) sensor short circuit – check connections to DHW sensor are in place |
| E34 | Mains supply voltage < 180V – may be a problem with your power supply |
| E35 | Mains supply frequency incorrect – may be a problem with the power supply |
| E37 | Water pressure error – increase water pressure |
| E38 | Reset key fault – replace fascia PCB |
| E40 | Water pressure too high |
| E41 | Communication error between fascia and control box – check cables |
| E43 | Return sensor short circuit – check connections to return sensor |
| E44 | Return sensor open circuit – check connections to return sensor are in place |
| E45 | Flue sensor short circuit – check connections to flue sensor |
| E46 | Communication error between fascia and control box – check cables |
| E99 | Flue sensor short circuit – check connections to flue sensor are in place |
S30 System Gas Boiler Error Codes
| Fault Code | Possible Cause |
|---|---|
| 0 | The boiler is in standby mode awaiting either a central heating call or hot water demand |
| C | The boiler has a call for central heating / hot water but the appliance has reached the desired temperature set on the boiler |
| C And Burner Light | The boiler is operating for central heating / hot water |
| F And Burner Light | The boiler is operating in frost mode |
| F0 | Boiler Chip Card (BCC) not fitted |
| F6 | Outside sensor failure |
| F7 | Low mains voltage |
| F9 | Printed circuit board (PCB) Fault |
| L5 | 5 boiler resets in 15 minutes |
| L6 | False flame lockout |
| C0 | Boiler Chip Card (BCC) activation fault |
| C2 | Boiler Chip Card (BCC) fault |
| F1 | Low water pressure |
| L1 | Flow temperature overheat |
| F2 | Flame loss |
| L2 | Flame loss |
| F3 | Fan fault |
| F4 | Control / No flow thermistor |
| F5 | Return thermistor |
C40 C55 Combi Gas Boiler
| Fault Code | Possible Cause |
|---|---|
| Enn | Fault causing a boiler shutdown |
| E00 | Flame detected when not expected – check boiler earth and probe condition |
| E02 | No ignition after restart – check gas supply, gas valve operation and ignitor electrode spark generation |
| E03 | Gas valve faulty or not connected |
| E04 | Power has been reset whilst boiler was in lockout |
| E11 | Internal electronics error – rest or replace control box |
| E18 | Flow overheat – check water circulation |
| E19 | Maximum return temperature exceeded – check circulation |
| E25 | Flow temperature increased too quickly – check water circulation |
| E30 | Difference between flow and return temperatures too high – check circulation. |
| E31 | Flow thermistor short circuit – check/replace connections/thermistor |
| E32 | Return thermistor short circuit – check/replace connections/thermistor |
| E36 | Flow thermistor open circuit – check/replace connections/thermistor |
| E37 | Return thermistor open circuit – check/replace connections/thermistor |
| E44 | Low water pressure |
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