Error E15

Safety first:

1) If you can smell gas (rotten egg smell or hissing), do not operate switches or the boiler. Turn off gas at the meter or appliance isolation if it is safe to do so, ventilate the area, leave the property and call the gas emergency number immediately.

2) If unsure, stop and call a Gas Safe engineer. Do not attempt internal electrical or gas valve repairs yourself.

Initial checks a homeowner can do (safe, non-intrusive):

1) Record the fault: write down the code (E15), any other codes shown, the boiler make/model and serial number, and the time the fault occurred.

2) Reset the boiler: try a single reset using the boiler reset button or control panel (hold for 3–5 seconds). Wait to see if the boiler attempts to start normally. If the code returns immediately or repeatedly, do not keep resetting.

3) Check household gas supply: test another gas appliance (hob, oven, gas fire) to confirm gas is available. If nothing lights, contact your gas supplier. If a single appliance fails, that appliance may be isolated; if your whole supply is off, the supplier must be contacted.

4) Check mains power: ensure the boiler has normal power and the supply fuse or RCD has not tripped. Low voltage or supply interruptions can cause valve/PCB errors.

5) Check system pressure and basic indicators: note system pressure on the gauge (many Potterton boilers prefer ~1–1.5 bar). Low pressure usually shows a different code but it is helpful to have correct pressure before an engineer attends.

6) Visual external inspection: with the boiler turned off at the mains, look for obvious signs of damage to cables, connectors, or water ingress at the boiler casing. Do not remove covers or touch internal components unless you are qualified.

If you are technically competent and choose one cautious additional check (only if you understand the risks):

1) Isolate the boiler electricity at the isolator and turn off the gas supply to the boiler.

2) Remove the outer casing only if you know how and are comfortable doing so. Visually inspect the gas valve wiring connector for loose pins, burned contacts, corrosion or detached wires. If you find a loose plug that simply needs seating, that may clear the fault, but only reconnect with power and gas isolated.

3) Reattach casing, restore gas and power, and attempt one controlled restart. If the E15 returns, replace the casing and stop further DIY attempts.

When to call a professional and what to tell them:

1) Call a Gas Safe registered engineer if E15 persists after the safe checks, if the code reappears immediately after reset, or if you found any suspicious wiring, water damage or burned connectors. Also call urgently if you smell gas or the boiler shows multiple gas-related fault codes.

2) Provide the engineer with: boiler make/model/serial, exact fault code(s), what you observed and the checks you performed (reset, gas supply test, visual inspection), and whether power supply dips were noticed.

Likely professional diagnostics and fixes the engineer will perform:

1) Confirm gas supply and mains voltage under load.

2) Use diagnostic tools to read detailed fault logs and confirm whether the issue is wiring, gas valve actuator, or PCB fault.

3) Check and test the gas valve electrical connections, measure coil resistance or valve actuator function, and test control signals from the PCB.

4) Replace or repair the gas valve actuator or connector if faulty; replace PCB if it is failing and confirmed to be the cause.

5) Re-test ignition and safety interlocks, check for flame detection and correct operation under normal running conditions.

Final notes:

- Do not continue to reset the boiler repeatedly — repeated lockouts may compound the issue.

- Any internal gas or electrical repairs must be carried out by a Gas Safe registered engineer for safety and to comply with regulations.

- If the fault appears alongside other codes (E09, E133, E134, E135 or voltage-related codes) mention these to the engineer — they help pinpoint wiring, supply or PCB problems.

- If in doubt, shut the boiler off and call a qualified engineer rather than attempting risky repairs yourself.