BoilerFaultCodesPotterton Overheat Limit Thermostat Fault Code
Also written as OVERHEATLIMITTHERMOSTAT — same fault.
The Potterton Overheat Limit Thermostat fault code means: your boiler has automatically shut itself down because it became too hot, acting as a safety measure to prevent damage.. It appears on 4 Potterton models in our database.
Technical description: The boiler is fitted with a safety thermostat to protect against overheating of the water. Should the boiler fail to light, allow it to cool and press the reset button.
What causes the Potterton Overheat Limit Thermostat fault?
This fault occurs when the water inside the heat exchanger reaches a dangerously high temperature, triggering a safety switch to cut the power. The most common reasons are a failed pump that isn't moving water around the system quickly enough or a blockage in the pipework caused by a build-up of sludge. It can also happen if the external controls fail to tell the boiler to turn off once the house is warm.
This issue often surfaces during the first cold spell of autumn when the heating system is turned back on after being idle all summer, which can cause internal parts like the pump to seize.
DIY fix possible
Wait for the boiler to cool down completely (at least 30 minutes).Locate the reset button, usually found under the front of the boiler casing.Press the button firmly to reset the thermostat; the boiler should then attempt to relight.
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Gas Safe Register →Potterton models that show the Overheat Limit Thermostat fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Potterton Overheat Limit Thermostat fault code information on this page is sourced and cross-checked against the official Potterton service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026