Baxi E110 means the boiler has overheated and locked itself out as a safety measure. It will not fire again on a reset alone if the cause is still there, and while a few causes are simple to rule out at home, most need an engineer to find and fix.
| What it means | What to do first | Who is needed |
|---|---|---|
| The boiler has overheated and tripped a safety lockout | One reset, a pressure check, and bleed any radiators that are cold at the top | A Gas Safe registered engineer if E110 returns |
| Usually caused by poor water circulation through the boiler | Do not open the casing or bypass the safety device | Diagnosis of the pump, sensor or diverter valve |
| Can look like a simple low-pressure fault at first | Note whether the fault returns straight after the reset | An engineer can flow-test the system and confirm the real cause |
What Does E110 Mean?
E110 is an overheat lockout. The boiler has detected that the water in the heat exchanger has gone above its safe temperature, so it has shut the burner down instead of carrying on. In most cases the burner is working normally and the real problem is that water is not moving through the boiler fast enough to carry the heat away. The exact wording and reset behaviour vary between Baxi models, so check the code against the instructions for your own boiler.
On Baxi EcoBlue boilers the same overheat fault shows as 110, without the E. Main and Potterton boilers come from the same manufacturer and use a similar code for the same problem.
Common Causes
The same E110 code can point to several different problems, and they do not all carry the same urgency or fix. Knowing roughly which one you are dealing with also helps when you speak to an engineer, because it narrows down what they need to check first.
| Cause | What it looks like |
|---|---|
| Low pressure | The gauge sits below the normal cold range |
| Air in the system | Cold spots at the top of one or more radiators |
| Radiator or isolation valves shut | Most radiators off at once, often after decorating or a recent repair |
| Faulty temperature sensor | False overheat readings even though the system seems fine |
| Seized pump or sticking diverter valve | Poor circulation, with the boiler cutting out soon after it fires |
| Sludge or a blocked heat exchanger | Cold patches at the bottom of radiators, gurgling or banging noises |
Low pressure, trapped air and shut valves are the causes a homeowner can often rule out or fix without any tools beyond the filling loop and a radiator key. If your boiler is showing a low-pressure code as well, our guide to the Baxi E1 fault code explains how to repressurise safely. A sensor, pump or valve fault needs testing equipment and parts, so those sit firmly with an engineer, even though the display shows the same E110 in every case.
What You Can Safely Check Yourself
- Reset the boiler once and see whether it keeps running.
- Check the cold pressure on the gauge and top up to the normal range with the filling loop if it is low.
- Make sure the radiator valves are open, especially if work has been done on the heating recently.
- Bleed any radiators that are cold at the top, then check the pressure again, because bleeding lets water out and can drop the pressure.
These checks cover the causes that do not need specialist tools. If one of them brings the boiler back and it stays running, the fault was most likely related to pressure, air or a shut valve.
What not to do matters just as much:
- Do not open the casing to look at the circuit board or wiring.
- Do not bypass the temperature sensor or the overheat safety device to force the boiler to stay on. That cut-out exists to stop damage to the heat exchanger.
- Do not keep resetting it if the fault comes straight back. Repeated resets with the same cause still present can add to the damage.
When to Call a Gas Safe Engineer
If the boiler trips E110 again after a reset, or the pressure and radiators were already fine, the cause is likely the sensor, the pump or the diverter valve, and all three need proper diagnosis. Only a Gas Safe registered engineer can legally work on the boiler, and you can check any engineer’s registration on gassaferegister.co.uk before they start.
An engineer diagnosing E110 will usually run a flow test to see how well water is moving through the system, check the temperature sensor’s resistance against its expected values to rule a false reading in or out, and inspect the pump and diverter valve for wear or seizure. A faulty sensor and a seized pump can cause the same lockout but test very differently, which is how an engineer separates one cause from another without replacing parts on a guess. Our boiler repair in London engineers carry out exactly these checks.
How Much Does a Repair Cost?
There is no single price for an E110 repair, because the code does not tell you the cause on its own. A pressure top-up and a radiator bleed cost nothing beyond your time. A pump or sensor replacement is a different job, with its own parts cost and labour time, and the only way to know which you are facing is to have an engineer diagnose it first. BeFix charges £95 per hour between 7am and 5pm, £125 per hour between 5pm and 9pm, and £160 per hour between 9pm and 7am, all plus VAT, with no call-out fee. If parts are needed, they are costed separately and confirmed once the engineer has found exactly what is wrong.
How to Help Prevent E110
Most E110 faults come down to circulation, so keeping the water in the system clean and moving freely is the best prevention. An annual service lets an engineer spot a tired pump or a sensor drifting out of range before it causes a lockout. A magnetic system filter and the right level of inhibitor in the water slow down the sludge that builds up in radiators and the heat exchanger over time. If you top up the pressure regularly, that is a sign of a leak worth fixing, because fresh water brings in more oxygen and speeds up the build-up of sludge.
Frequently Asked Questions
What does E110 mean?
E110 is an overheat lockout. The boiler has shut the burner down because the water temperature inside it went above its safe limit, usually because water is not circulating fast enough to carry the heat away.
Can I reset the boiler myself?
Yes, a single reset is safe to try. If the boiler fires up and keeps running, the fault may have been a one-off. If E110 comes back straight away, stop resetting it and get an engineer to look at it, since repeated resets will not fix the underlying fault and can add to the strain on the system.
Is it safe to keep resetting the boiler if E110 only happens once a day?
No. Once a day is still a pattern, which means the cause has not gone away between resets. The lockout happens because the boiler really did overheat, and forcing it back on again and again risks more damage to the heat exchanger or pump. It is better to have it looked at before it stops resetting altogether.
Is E110 the same as low pressure?
No, but low pressure is one of the things that can trigger it. E110 is the overheat lockout itself, and low pressure is one of several possible causes, alongside air in the radiators, shut valves, a faulty sensor, or a pump or valve problem. Checking the pressure gauge is the quickest way to rule that cause in or out.
Can bleeding radiators fix E110?
It can, if trapped air was the cause. Air pockets stop water circulating properly, which lets the temperature at the heat exchanger climb even though the boiler itself is working normally. Bleeding the affected radiators restores the flow. Check the pressure afterwards, because bleeding can drop it below the normal range.
My pressure and radiators look fine. What causes E110 then?
If the pressure is normal and the radiators heat evenly, the cause is most likely a faulty temperature sensor giving a false overheat reading, or a seized pump or sticking diverter valve slowing the flow through the boiler. These are told apart by testing: the sensor’s resistance is checked against its expected value, and the pump and valve are checked by how well water is moving. An engineer can usually confirm which one it is in a single visit.
If an E110 lockout does not clear with a reset, a pressure check and a radiator bleed, the next step is proper diagnosis. BeFix (Gas Safe 967796) repairs boilers across London, and our engineers can flow-test the system and check the sensor, pump and diverter valve to find out what is behind the fault. Call 020 8058 4241 to book.
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