Overview
F0 on a Keston S30 system boiler means the boiler control has detected that the Boiler Chip Card (BCC) is missing or not recognised. The BCC is a small configuration/identification module on the boiler’s control electronics that the PCB expects to be present and correctly seated. Without a valid BCC the boiler can refuse to start or go into a lockout state because the control board either cannot read required configuration data or it treats the PCB as unconfigured. This fault is primarily an electrical/configuration issue rather than a gas or combustion safety fault, but it will prevent the boiler supplying heating or hot water in normal operation. In many cases the cause is simple: the card has come loose, been removed, or its contacts are dirty or corroded. However the error can also indicate a failing PCB, a damaged BCC, or an unconfigured replacement board. Initial checks and a simple reseat may be done by a competent homeowner, but if the fault stays present you should contact a Gas Safe Registered Engineer (or RGII in Ireland) or the manufacturer if the boiler is under warranty — do not attempt PCB or gas-related repairs yourself.
Possible Cause: Boiler Chip Card (BCC) not fitted
Troubleshooting Steps
Safety first: before doing anything isolate electrical supply to the boiler at the fused spur or consumer unit. Do not work on gas or live electrical parts unless you are qualified. Keep panels and covers in place unless you are confident and competent to remove them; removing covers can expose live terminals, hot surfaces and gas components.
Initial checks a homeowner can do:
1) Check the display and controls: ensure mains power to the boiler is on and external controls (programmer, room thermostat, cylinder stat) are calling for heat. Note the exact display code (F0) and whether any other codes are shown.
2) Try a simple restart: press the Restart button on the boiler fascia (with power on). Wait for the ignition sequence. If the fault clears and boiler runs, monitor operation for a while.
3) Check system pressure: ensure central heating pressure is in the normal range (typically around 1.0–1.5 bar when cold). Some faults will persist if pressure is abnormally low.
4) Check mains supply: if the household has low mains voltage or recent electrical issues, that can cause PCB/configuration faults. Confirm other electrical devices are operating normally.
If you are comfortable exposing the boiler controls and the boiler is isolated from mains power, basic BCC checks you can perform:
1) Isolate electricity to the boiler at the fused spur or consumer unit. Wait a minute for capacitors to discharge.
2) Remove the outer front panel/fascia only if you are confident and follow the boiler manual instructions for access. Never remove panels while power is live.
3) Locate the Boiler Chip Card (BCC) — a small plug-in card or module on the PCB/fascia area as described in the manual. Visually check its seating: it may have become loose or partially withdrawn.
4) If the card appears loose, gently remove it by pulling straight out, inspect the contact edge for deposits, dirt or corrosion, and blow any dust away (use dry compressed air or a soft brush). Do not use liquids or abrasive cleaners.
5) Reinsert the card firmly and evenly into its slot until fully seated. Refit the fascia and restore power.
6) Use the Restart button and observe the display. If F0 clears and normal codes (00/On/C) return, run the boiler and confirm heating/hot water operate normally.
If the F0 code remains after reseating the card, or if the card is missing/damaged, or you are uncomfortable removing panels:
- Do not continue working on the PCB or internal components. Persistent F0 can indicate a faulty BCC, a damaged or unconfigured PCB, or other electronic faults that require specialist tools and parts.
- Contact a Gas Safe Registered Engineer (or RGII in Ireland). If the appliance is under warranty contact Keston technical support before having repairs done. Tell the engineer the boiler model (S30) and that the display shows F0 (Boiler Chip Card not fitted) so they can bring appropriate spares if needed.
Important notes:
- Do not attempt to operate the boiler with covers removed or with makeshift repairs to the PCB or wiring. Working on gas valves, burners or control electronics requires a qualified engineer.
- If a replacement PCB or BCC is fitted it may need configuration/activation; this is typically a job for the manufacturer or a qualified gas engineer.
- If you smell gas or suspect a gas leak at any time, isolate the gas supply, evacuate the building and call the gas emergency number immediately.
Helpful Resources
Boiler Manual
Download the official PDF manual for the Keston S30 System Gas Boiler.