Flue overheat lockout
The E131 error code on Potterton boilers indicates flue overheat lockout.
Potterton E131 means: flue overheat lockout. On this component the documented failure modes are heat exchanger fouled or partially blocked, no water circulation: pump blocked, seized or not running or safety thermostat or overheat limit tripped. A Gas Safe registered engineer should diagnose the root cause.
What Does E131 Mean
The E131 code is shown by the boiler’s control board when it detects flue overheat lockout. The boiler then stops instead of continuing to run in that condition: the code is the appliance reporting a problem, not proof that the boiler is broken.
| What you see on the boiler |
|---|
| The display shows E131 and the boiler stops until the fault is cleared |
Common Causes
The manufacturer does not publish a cause list for this specific code. The causes below are the failure modes documented for the same component on other boilers, confirmed by the service literature of 10 different manufacturers.
| Cause |
|---|
| Heat exchanger fouled or partially blocked |
| No water circulation: pump blocked, seized or not running |
| Safety thermostat or overheat limit tripped |
Safety Warning
E131 is a gas-related fault. Never attempt to repair or adjust the gas valve, burner assembly, or flue system yourself. All gas work must be carried out by a Gas Safe registered engineer (UK) or licensed HVAC technician (US). Repeated resets after ignition failure can cause unburnt gas to accumulate inside the combustion chamber — this is a serious safety hazard. If you smell gas at any point, turn off the gas supply at the meter, open windows, leave the property, and call your gas emergency service immediately. Gas-related fault. Do not open the boiler casing or attempt repairs to the gas valve, burner, ignition or flue. Repeated resets are unsafe. Diagnosis and repair must be carried out by a Gas Safe registered engineer.
Parts & Prices
Prices shown are indicative. Actual prices and availability vary by region.
Step-by-Step Diagnosis
1. Verify gas supply — check gas meter is on and other gas appliances work. 2. Inspect the ignition electrode — look for cracks, carbon build-up, or incorrect gap (typically 3-4mm). 3. Check the ignition lead — ensure it is securely connected and not damaged. 4. Test the gas valve — measure voltage at the gas valve terminals during ignition attempt (should read 24V AC or mains depending on model). 5. Inspect the flue system — check for blockages, birds' nests, or debris. 6. Check the condensate trap and drain — a blocked condensate pipe can prevent ignition. 7. Verify the ionisation probe is clean and correctly positioned. 8. If all above pass, test the PCB by measuring outputs during ignition sequence
How to Fix It
Have the heat exchanger inspected and cleaned; if it is blocked by limescale or sludge the system needs a chemical flush and an inhibitor dose.
Check the pump is receiving power and turning freely; free a seized shaft or replace the pump if it does not run.
Establish why the boiler overheated — usually no circulation — before resetting. Then check the continuity of the safety thermostat and replace it if it stays open when cold.
Refer to the Potterton service documentation for the detailed procedure. Only a qualified engineer should carry out these repairs.
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Affected Models
Potterton models that can display fault code E131:
| Model Family | Output Range | Frequency |
|---|---|---|
| All Potterton models | — | Possible |
Frequently Asked Questions
Have the heat exchanger inspected and cleaned; if it is blocked by limescale or sludge the system needs a chemical flush and an inhibitor dose. According to the technical documentation, this is the first check on the list for E131.
E131 is classified as a high-severity fault: it involves gas, combustion or flue components. Do not keep resetting the boiler and do not attempt the repair yourself — call a Gas Safe registered engineer.