Common Boiler Problems

Keston Boilers

As professional Gas Safe Register installers for Keston gas boilers and OFTEC registered installers for Keston oil-fired boilers throughout north London, BBS Plumbing and Heating are also are fully qualified and experienced to service, upgrade and repair all Keston boiler types, and carry out repairs to existing hot water and central heating systems.

Fault finding main menu.

Combi Boilers – Combi 30 / Combi 35

Boiler status display information is shown – up to six messages in rotation
– as described below:

FaultRemedy
Overheat lockout1 Fill system to 1.0 bar; 2 Bleed radiators; 3 Check radiator valves open; 4 Reset boiler; 5 Contact installer
Ignition lockout / Flue Overheat 1 Check other gas appliances work; 2 Reset boiler; 3 Contact Installer
Too many resetsContact Installer
Fault 8Contact Installer
Low water pressure1 Fill system to 1.0 bar; 2 Bleed radiators; 3 Contact installer
Flame loss1 Check other gas appliances; 2 Contact installer
Fan faultContact Installer
Return thermistor faultContact Installer
Outside sensor faultContact Installer
Low mains voltageContact electricity provider
PCB FaultContact Installer
PCB ReplacedReset boiler
Flow thermistor faultContact Installer
Boiler Chip Card FaultContact Installer
12 month service interval requestContact Installer

Please Note: The above information is for guidance only. You will need to call an qualified and experienced Gas Safe Keston service engineer, such as BBS Plumbing and Heating, for further advice.

Combi Boilers – C36 / C36P

Fault Modes

If a situation is detected, which the boiler considers may cause damage to the appliance the boiler will enter a lockout mode and stop functioning. After clearing the problem the “reset” button must be pressed once to resume boiler operation.

Please note :Switching the power ON and then OFF will not clear a boiler lockout.

Error Codes

DisplayDescription of fault
E01Ignition failure – the boiler has attempted to light five times and not succeeded.
E02False flame – the unit is detecting a flame BEFORE ignition.
E03Boiler overheat.
E05Fan failure – boiler cannot detect fan rotation.
E07Flue overheat.
E08Flame circuit error – possible control box fault.
E09Valve drive error – possible gas valve or control box fault.
E10Control box errors – possible faulty control box.
E11The automatic test for calibration of flow and return sensors has failed.
E12- E22 Control box errors – possible faulty control box.
E23Water filling error.
E24 Water pressure lost 4 times in 24 hours – possible leak.
E25Control box errors – possible faulty control box.
E26Flame signal lost 5 times in 4 minutes – the flame is unstable.
E30Flow sensor short circuit.
E31Flow sensor short circuit.
E32DHW sensor short circuit.
E33DHW sensor short circuit.
E34Mains supply voltage < 180V.[/av_cell][/av_row] [av_row row_style=''][av_cell col_style='']E35[/av_cell][av_cell col_style='']Mains supply frequency incorrect.[/av_cell][/av_row] [av_row row_style=''][av_cell col_style='']E37[/av_cell][av_cell col_style='']Water pressure error.[/av_cell][/av_row] [av_row row_style=''][av_cell col_style='']E38[/av_cell][av_cell col_style='']Reset key fault – replace fascia PCB.[/av_cell][/av_row] [av_row row_style=''][av_cell col_style='']E40[/av_cell][av_cell col_style='']Water pressure too high.[/av_cell][/av_row] [av_row row_style=''][av_cell col_style='']E41[/av_cell][av_cell col_style='']Communication error between fascia and control box.[/av_cell][/av_row] [av_row row_style=''][av_cell col_style='']E43[/av_cell][av_cell col_style='']Return sensor short circuit.[/av_cell][/av_row] [av_row row_style=''][av_cell col_style='']E44[/av_cell][av_cell col_style='']Return sensor short circuit.[/av_cell][/av_row] [av_row row_style=''][av_cell col_style='']E45[/av_cell][av_cell col_style='']Flue sensor short circuit.[/av_cell][/av_row] [av_row row_style=''][av_cell col_style='']E46[/av_cell][av_cell col_style='']Flue sensor short circuit.[/av_cell][/av_row] [av_row row_style=''][av_cell col_style='']E99[/av_cell][av_cell col_style=''] Communication error between fascia and control box.[/av_cell][/av_row] [/av_table][av_textblock size='' font_color='' color=''] Please Note: The above information is for guidance only. You will need to call an qualified and experienced Gas Safe Keston service engineer, such as BBS Plumbing and Heating, for further advice.

Combi Boilers – C45 / C40P / C55 / C55P

Fault Modes

Automatic Lockout Avoidance

The boiler will react to adverse conditions in two ways. If the fault is not severe, or is not persistent, the boiler will halt (or block) operation for a set time before it attempts to fire again.
During this block time the block code will be displayed, alternately with the code “9 nn”, where nn is the boiler flow temperature.

Block Codes
[/av_textblock]Display

Reason for Block
B 18Flow temperature exceeds 95 deg C
B 19Return temperature exceeds 95 deg C
B 24Return temperature exceeded flow temperature.
B 25Flow temperature climbing too quickly – possible airlock or circulation blockage.
B26Low water pressure.
B28No signal from fan – possible fan disconnected or faulty.
B29Incorrect signal from fan – possible fan faulty.
B 30 Difference between flow and return temperatures too high.
B 65Waiting for fan to start.

Lockout

If the fault is persistent or more severe the boiler will lockout with a error code. When the boiler has entered this error mode it will not attempt to restart until the “Reset” button is pressed.

Error Codes

DisplayDescription
E 00Flame detected when not expected.
E 02No ignition after restart.
E 03Gas valve faulty or not connected.
E 04 Power has been reset whilst boiler was in lockout.
E 11Internal electronics error.
E 12Thermal fuse blown or flue overheat thermostat activated.
E 18Flow overheat.
E 19Maximum return temperature exceeded.
E 25 Flow temperature increased too quickly.
E 28Fan not rotating.
E 30 Difference between flow and return temperatures too high.
E 31 Flow thermistor short circuit.
E 32Return thermistor short circuit.
E 36Flow thermistor short circuit.
E 37Return thermistor short circuit.
E 44Low water pressure.

Please Note: The above information is for guidance only. You will need to call an qualified and experienced Gas Safe Keston service engineer, such as BBS Plumbing and Heating, for further advice.

System Boilers

System 30

Basic Troubleshooting

NO Central Heating or NO Hot Water
STEP 1 Check the mains switch (fused spur) is turned on and ensure mode control knob (B) is in the ON position.
STEP 2Check the programmer is at the “ON” position and the room thermostat is turned up.
STEP 3Does the boiler operate an provide central heating? YES – Check the time settings on the programmer are as required and adjust if necessary. NO – See boiler “Fault Codes” section. If “0” is displayed then contact a Gas Safe Registered Engineer for further advice.

Please Note: The above information is for guidance only. You will need to call an qualified and experienced Gas Safe Keston service engineer, such as BBS Plumbing and Heating, for further advice.

Fault Codes

Display Code
StatusStatusFault
F0Boiler Chip Card (BCC) not fitted.
F6 Outside sensor failure. Reset the appliance – if the boiler fails to operate then please contact Keston (if under warranty) or alternatively a Gas Safe Registered Engineer.
F7Low Mains Voltage.
F9 PCB Fault.
L5 5 Boiler Resets in 15 minutes – Turn power off and on at the fused spur.
L6 False Flame Lockout.
C0 BCC Activation Fault.
C2 BCC Fault.
F1Low Water Pressure – Check system pressure is between 1 and 1.5 bar on the pressure gauge.
L1Flow Temperature Overheat – Check system pressure is between 1 and 1.5 bar on the pressure gauge.
F2Flame Loss – Check other gas appliances in the house are working to confirm a supply is present in the property. If other appliances do not work or there are no other appliances check the gas supply is on at the meter and/or pre payment meter has credit.
L2Flame Loss – Check other gas appliances in the house are working to confirm a supply is present in the property. If other appliances do not work or there are no other appliances check the gas supply is on at the meter and/or pre payment meter has credit.
F3 Fan Fault – Reset the boiler.
F4Control / No Flow Thermistor – Reset the boiler.
F5 Return Thermistor – Reset the boiler.

Please Note: The above information is for general guidance only. If a reset of the boiler fails to clear the fault code and the boiler fails to operate then please call a qualified and experienced Gas Safe Keston service engineer, such as BBS Plumbing and Heating, for further advice.

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