Main E110 fault code explained

If a Main boiler shows E110, Baxi’s official fault-code table gives two related meanings: the boiler’s maximum temperature has been exceeded too quickly, possibly because water is not circulating as expected, or the safety thermostat sensor has tripped.

This is an over-temperature safety fault. Let the boiler cool, keep the casing closed and use only the reset method in the user guide for your exact model. If E110 returns, arrange an engineer visit rather than repeatedly resetting the appliance.

What does Main fault code E110 mean?

The manufacturer describes E110 as either:

• the boiler’s maximum temperature being exceeded for the measured temperature gradient, with air or restricted circulation listed as possible explanations; or
• the safety thermostat sensor having tripped.

The display code does not prove that any one component has failed. An engineer must check the boiler and heating system to determine why the temperature rose abnormally.

Which Main boilers use E110?

Baxi’s current error-code table includes E110 in the group covering the Main Eco Compact Combi and Main Eco Compact System, alongside several related Baxi and Potterton ranges. That does not mean every Main boiler uses the same code. Check the model name on the outside of the boiler and use its official user guide.

What can I check safely?

Without opening the boiler, you can gather useful information:

• Photograph the E110 display.
• Check the exact model and whether it is a combi or system boiler.
• Look at the external pressure gauge and compare it with the normal range in the user guide.
• Check whether any radiators are warming and whether several radiator valves have been closed.
• Listen for unusual banging, kettling or rushing-water sounds, but do not remove covers to investigate them.
• Note whether the code appeared during heating, hot-water use or immediately after a reset.

Do not remove the casing, touch the pump, sensors or wiring, or try to release air from inside the boiler. E110 can involve high temperatures, so internal checks belong to a suitably qualified engineer.

Can I reset a Main E110 fault?

First allow the appliance to cool. If your exact user guide permits a normal user reset, try it once. If the boiler restarts, watch it from a safe distance and note whether the code returns when heating or hot water is requested.

Do not keep resetting E110. A repeated over-temperature lockout means the underlying circulation or safety issue has not been resolved.

Why might the boiler overheat?

The code can be associated with poor circulation, air in the heating circuit or a safety thermostat event, but the display alone cannot identify the cause. The engineer may need to assess system pressure, circulation, controls, sensors and the boiler’s operating history. This is diagnosis, not a reason to replace a particular part automatically.

When should I switch the boiler off?

Switch the appliance off and arrange prompt professional advice if E110 returns, the boiler makes severe banging noises, water leaks near electrical parts, or the appliance becomes unusually hot. If you smell gas or a carbon-monoxide alarm sounds, follow the Gas Safe Register’s emergency guidance and do not operate electrical switches or attempt a reset.

What should I tell the engineer?

Provide the exact code and model, a photo of the display and pressure gauge, when the fault occurs, whether radiators were heating, any unusual noises and whether one reset changed anything. Mention recent work on radiators, controls or the heating system.