Whether it be a combi, system or heat only model, a Keston boiler will always display a fault code when an error occurs. The fault codes will be easy to spot on the display, and the boiler will automatically enter a lockout mode and stop operating when a fault code appears. Keston boiler fault codes should make it easier for your engineer to identify faults and fix your boiler problems. Once faults are cleared by your engineer, your Keston boiler must be reset by pressing the reset button so that the boiler can return to normal working order.
If a fault code has appeared on your Keston boiler and you want to know what it means, you can find the fault description and possible cause in the table below.
Keston Boiler Fault Codes
| FAULT CODE | DESCRIPTION / POSSIBLE CAUSE |
|---|---|
| B18 | Flow temperature exceeded 95°C. |
| B19 | Return temperature exceeded 95°C. |
| B24 | Return temperature exceeded flow temperature. Check pump direction on the boiler and any external pumps, and check that the wires on the flow and return thermistors are not crossed. |
| B25 | Flow temperature climbing too quickly. Possible air lock or circulation blockage. |
| B26 | Low water pressure. |
| B28 | No signal from fan. Fan could be faulty or disconnected. |
| B29 | Incorrect signal from fan. Fan could be faulty. |
| B30 | Difference between flow and return temperatures too high. Check water circulation. |
| B65 | Waiting for the fan to start. |
| E00 | Flame detected when not expected. Check the boiler earth and probe condition. |
| E02 | No ignition after restart. Check gas supply, gas valve operation and ignitor electrode spark generation. |
| E03 | Gad valve is faulty or not connected. |
| E04 | Power has been reset whilst the boiler was in lockout. |
| E05 | Fan failure. The boiler cannot detect fan rotation. |
| E07 | Flue overheat. |
| E08 | Flame circuit error. Possible fault with the control box. |
| E09 | Valve drive error. Possible fault with the gas valve or control box. |
| E10 | Control box error. Possible fault with control box. |
| E11 | Internal electronic error. Reset or replace control box. |
| E12 | Thermal fuse has blown or flue overheat thermostat activated. |
| E18 | Flow overheat. Check the water circulation. |
| E19 | Maximum return temperature exceeded. Check circulation. |
| E13, E14, E21 or E22 | Control box error. Possible fault with control box. |
| E23 | Water filling error. |
| E24 | Water pressure lost 4 times in 24 hours. Possible leak. |
| E25 | Control box errors. Possible fault with control box. |
| E26 | Flame signal lost 5 times in 4 minutes. The flame is unstable. |
| E28 | Fan is not rotating. Check fan connection and fan for fault. |
| E30 | Difference between flow and return temperatures too high. Check circulation. |
| E31 | Flow thermistor short circuit. Check or replace connections or thermistor. |
| E32 | Return thermistor short circuit. Check or replace connections or thermistor. |
| E36 | Flow thermistor open circuit. Check or replace connections or thermistor. |
| E37 | Return thermistor open circuit. Check or replace connections or thermistor. |
| E44 | Low water pressure. |
| F0 | Boiler chip card (BCC) not fitted. Contact Keston if boiler still under warranty or contact a Gas Safe registered engineer if boiler outside warranty. |
| F6 | Outside sensor failure. Boiler needs to be reset. Follow the resetting instructions. If a reset doesn’t resolve the issue, contact Keston if boiler still under warranty or contact a Gas Safe registered engineer if boiler outside warranty. |
| F7 | Low mains voltage. Contact a qualified electrician or your electricity provider. |
| F9 | PCB (printed circuit board) fault. Contact Keston if boiler still under warranty or contact a Gas Safe registered engineer if boiler outside warranty. |
| L5 | 5 boiler resets in 15 minutes. Turn the power off and on at the fused spur.2. If the boiler still doesn’t work, contact Keston if boiler still under warranty or contact a Gas Safe registered engineer if boiler outside warranty. |
| L6 | False flame lockout. Boiler needs to be reset. Follow the resetting instructions. If a reset doesn’t resolve the issue, contact Keston if boiler still under warranty or contact a Gas Safe registered engineer if boiler outside warranty. |
| C0 | BCC start fault. Boiler needs to be reset. Follow the resetting instructions. If a reset doesn’t resolve the issue, contact Keston if boiler still under warranty or contact a Gas Safe registered engineer if boiler outside warranty. |
| C2 | BCC fault. Boiler needs to be reset. Follow the resetting instructions. If a reset doesn’t resolve the issue, contact Keston if boiler still under warranty or contact a Gas Safe registered engineer if boiler outside warranty. |
| F1 | Low water pressure. Check the system pressure is between 1 and 1.5 bar on the pressure gauge. If the boiler still doesn’t work properly, contact Keston if boiler still under warranty or contact a Gas Safe registered engineer if boiler outside warranty. |
| L1 | Overheat of temperature flow. Verify if the pressure on the gauge is between 1 and 1.5 bar. If the boiler still doesn’t work properly, contact Keston if boiler still under warranty or contact a Gas Safe registered engineer if boiler outside warranty. |
| F2 | Flame loss. Check that the other gas appliances in your home are working to confirm a supply is present in the property. |
| L2 | Flame loss. If your other gas appliances don’t work or there are no other appliances, check the gas supply is on at the meter or check the pre-payment meter has credit. |
| F3 | Fan fault. Boiler needs to be reset. Follow the resetting instructions. If a reset doesn’t resolve the issue, contact Keston if boiler still under warranty or contact a Gas Safe registered engineer if boiler outside warranty. |
| F4 | Control / No flow thermistor. Boiler needs to be reset. Follow the resetting instructions. If a reset doesn’t resolve the issue, contact Keston if boiler still under warranty or contact a Gas Safe registered engineer if boiler outside warranty. |
| F5 | Return thermistor. Boiler needs to be reset. Follow the resetting instructions. If a reset doesn’t resolve the issue, contact Keston if boiler still under warranty or contact a Gas Safe registered engineer if boiler outside warranty. |
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