BoilerFaultCodesWorcester Bosch Boiler overheat thermostat Fault Code
Also written as BOILEROVERHEATTHERMOSTAT — same fault.
The Worcester Bosch Boiler overheat thermostat fault code means: your boiler has become too hot and has automatically shut itself down to prevent damage or safety issues.. It appears on 1 Worcester Bosch model in our database.
Technical description: Reset Button - Boiler overheat thermostat
What causes the Worcester Bosch Boiler overheat thermostat fault?
This fault occurs when the water inside the boiler reaches an unsafe temperature, triggering a safety switch to cut the power. The most common reasons include a failing pump that isn't moving water away quickly enough or a buildup of limescale and sludge that restricts flow through the heat exchanger.
This issue is more frequent in autumn when heating systems are first turned on after a long summer break, as stagnant debris can settle and block the pump.
DIY fix possible
Wait at least 30 minutes for the boiler to cool down completely.Locate the reset button (usually behind the small circular flap or on the main control panel).Press and hold the reset button for five seconds to see if the boiler restarts.Check that your radiator valves are open and your system pressure is between 1 and 1.5 bar.
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Gas Safe Register →Worcester Bosch models that show the Boiler overheat thermostat fault code
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Source
Worcester Bosch Boiler overheat thermostat fault code information on this page is sourced and cross-checked against the official Worcester Bosch service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026