BoilerFaultCodesMain E110 Fault Code
The Main E110 fault code means: your boiler has switched itself off because it has reached an unsafe temperature, usually due to a lack of water flow or a circulation problem.. It appears on 5 Main models in our database.
Technical description: Safety thermostat operated
What causes the Main E110 fault?
This fault occurs when the water inside the boiler gets too hot, triggering a safety switch to prevent damage. The most common reasons are a pump failure that stops water from moving or a blockage in the system pipes that traps heat inside the heat exchanger.
This issue is more frequent when the heating is first turned on in autumn, as circulation pumps can seize up after being inactive throughout the summer.
DIY fix possible
Check if your radiator valves are openCheck the boiler pressure gauge and top up to 1.5 bar if lowPress the 'R' or 'Reset' button for 2 seconds once the boiler has cooled down
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Main models that show the E110 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Main E110 fault code information on this page is sourced and cross-checked against the official Main service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026