A plain E110 on the Baxi boiler families listed in the manufacturer’s current UK fault table is a high-temperature safety fault. Baxi describes two possible meanings: the maximum boiler temperature has been exceeded for its rate of rise, with a jammed pump or air in the circuit given as probable examples, or the safety thermostat sensor has tripped.
That wording is a starting point for a qualified diagnosis, not a parts order. The display cannot tell a homeowner whether the pump, circulation, sensor, wiring or another condition caused the boiler to protect itself. Do not remove the case or try to make the boiler keep firing.
What Baxi E110 means
Baxi’s UK error-code page lists E110 for a group that includes Platinum Compact, Duo-tec Compact, Megaflo Compact System, Main Eco Compact, earlier Baxi 600 and 800 Combi/System, Duo-tec, Assure, Platinum, Platinum+, Megaflo and EcoBlue products. Its published meaning is:
- boiler maximum temperature exceeded for gradient, with a probably jammed pump or air in the circuit; or
- safety thermostat sensor tripped.
“Gradient” refers to how quickly the measured temperature rises. If heat is being produced but water is not carrying it away as expected, the temperature can climb too rapidly and the control can stop the boiler. A safety trip is doing its job; repeatedly resetting around it is not a repair.
Check the exact code and model first
Photograph the complete display, including dots and leading zeros. Newer Baxi Combi 2 and System 2 ranges use longer codes such as E.04.08 for a maximum safe temperature value reached, E.01.17 for no water circulation and H.01.14 or H.01.18 for maximum flow-temperature conditions. Those are not interchangeable with plain E110.
Find the full model name from the front fascia, user guide, warranty record or Benchmark commissioning sheet. “Baxi 600” may not be enough because different generations use different control platforms. Do not unscrew the case to look for an internal label.
Is E110 an overheating fault?
It is a high-temperature safety code on the listed range, but “overheating” does not identify the failed part. Possible circulation-related explanations may include restricted water movement, air, an internal pump problem or a sensor/control issue. Only tests against the correct Baxi service information can separate them.
Do not assume a pump is definitely jammed because Baxi gives it as a probable example. The word “probable” matters. Buying a pump from the code alone can waste money and leave the actual fault unresolved.
What can a homeowner safely check?
- Let the boiler stop and cool; do not force repeated operation.
- Photograph the code and any symbol or alternating number.
- Record whether the fault happened during heating, hot-water use or both.
- Read the normal user-facing pressure gauge without removing covers.
- Note whether radiators had recently been bled, altered or left with valves closed.
- Check that normal external heating controls are calling for heat as expected.
- Use the exact user manual to decide whether one reset is permitted.
These observations help an engineer; they do not prove the cause. If the boiler is unusually hot, noisy, leaking, or E110 returns, switch it off with its normal control and arrange a repair.
Should I top up the pressure?
Only follow the model’s user instructions if its gauge is genuinely below the stated normal range. E110 itself is not Baxi’s published low-pressure code. On the same plain-code family, Baxi lists E118 for water pressure below 0.5 bar; newer ranges use other identifiers such as A.02.06.
Adding water when pressure is already normal will not restore circulation and can create an over-pressurised system. Repeatedly topping up can also hide a leak or another problem.
Should I bleed the radiators?
Do not bleed every radiator simply because E110 mentions air as a possibility. Radiator bleeding is a user task only where there is a clear symptom, such as a radiator cold at the top, and the boiler is off and cool. It lowers pressure in a sealed system and may make matters worse if done without a reason.
If air keeps returning, pressure keeps falling or the safety code recurs, stop treating the symptom. A competent engineer should establish why circulation is affected.
Did E110 start after work on the heating system?
Tell the engineer if the fault first appeared after a radiator was changed, the system was drained, a valve was replaced or the boiler was serviced. That timing does not prove trapped air or an installation mistake, but it is useful evidence when a rapid temperature rise and circulation are being assessed.
Also note whether all radiator valves were closed when the fault occurred and whether any rooms now heat differently. Do not start opening boiler panels or adjusting a bypass. The correct flow path depends on the system design, and an engineer should confirm it against the installation and the Baxi instructions.
Can I reset Baxi E110?
Baxi publishes different reset methods because control panels vary. Some use a dedicated reset button, while others use a selector switch or thermostat control. Follow only the exact boiler’s user guide. One reset after the appliance has cooled may show whether the event was temporary.
Baxi advises that frequent lockout indicates a fault and that an installer or service engineer should be contacted. Do not keep cycling the power, holding the reset control or raising demand to test whether it will run.
Why this is not an internal DIY repair
Investigating a pump, temperature sensor, wiring, internal filter or boiler waterway involves the inside of a gas appliance and may also expose mains electricity and hot water. Gas Safe Register explains that a case secured with screws can form part of the combustion circuit. Consumers should not remove it.
Never turn an internal pump shaft, bridge a thermostat, unplug a sensor, drain the boiler, open an automatic air vent or dismantle a filter. A Gas Safe registered engineer competent for the Baxi model should use the manufacturer’s service procedures and confirm safe operation afterwards.
What an engineer may investigate
Without assuming the outcome, the engineer can confirm the model and code family, examine system pressure and circulation, test the relevant temperature and safety devices, inspect connections, and compare live behaviour with Baxi data. The history matters: a fault after system work, radiator changes or a drain-down may point the investigation differently from a spontaneous lockout.
After any repair, the boiler must be checked for safe combustion, correct operation and a stable temperature response. Clearing the code alone is not the same as proving the fault has been corrected.
What to tell the repair booking team
- the complete code, including whether it is E110 or a dotted version;
- the exact Baxi model and approximate age;
- the cold pressure reading;
- whether heating, hot water or both were in use;
- whether radiators were recently bled or the system was drained;
- any gurgling, kettling or unusual heat; and
- whether one correct reset cleared the code temporarily.
A display photograph is more useful than saying the pump has failed. It preserves the exact evidence and avoids a diagnosis based on a similar-looking code.
When E110 is an emergency
An E110 lockout by itself normally calls for a controlled repair rather than a gas emergency. However, if you smell gas, a carbon monoxide alarm operates, anyone feels unwell, or there is water near electrical parts, do not continue troubleshooting. Leave the appliance alone and follow the appropriate official emergency guidance.
For a gas escape in Great Britain, call the National Gas Emergency Service on 0800 111 999 from a safe place. Do not operate electrical switches or use a flame to investigate.
Frequently asked questions
Does Baxi E110 mean the pump has failed?
No. Baxi mentions a probably jammed pump or air as examples under the excessive-temperature meaning, but the code does not identify a failed component on its own.
Is E110 caused by low pressure?
Not as its published definition. Record the pressure, but do not refill a normally pressurised system to chase E110.
Will turning every radiator valve on fix it?
It may be useful to tell the engineer how the valves were set, but changing them is not a substitute for diagnosis. If the boiler has tripped, let it cool and follow the manual.
Can I use hot water while E110 is showing?
If the boiler is locked out, do not defeat the lockout. If it still operates but displays a fault, switch it off and obtain model-specific advice.
Related boiler-help guides
- Baxi boiler fault codes
- Baxi E125 water circulation fault
- Why is my boiler overheating?
- Baxi boiler pressure guide
Has your Baxi stopped with E110?
Book a fixed-price Incredaboil boiler repair so the high-temperature safety fault can be checked against the correct Baxi model.