Baxi E110 fault code: what it means and how to fix it

What does the Baxi E110 fault code mean?

The Baxi E110 fault code means the boiler has overheated — its maximum temperature was exceeded and the safety thermostat tripped, usually because the pump is jammed or there's air in the system. There's very little to fix yourself: at most check the pressure. E110 is a safety lockout that needs a Gas Safe registered engineer — don't keep resetting it.

In plain terms, heat couldn't move away from the heat exchanger quickly enough, the temperature spiked, and a safety sensor stepped in and shut the boiler down. E110 shows up across Baxi's combi range, so the meaning is the same whether you're on an 800-series or an older model — it's always worth checking it against your own boiler's manual to be sure.

Try to see the lockout as the boiler doing its job. It noticed it was running too hot and stopped rather than carry on — that's a safety feature working, not a hazard in itself. What it is telling you is that something inside needs looking at, and repeatedly clearing it won't make that go away.

Key facts

The quick version before the detail.

• What it means: overheat — the safety thermostat has tripped (a jammed pump or trapped air is the usual cause).
• DIY-fixable: no — at most check the pressure and bleed the radiators once.
• Never keep resetting an overheat fault — it masks the problem and can add wear.
• Gas Safe job: the pump, heat exchanger and system cleaning are engineer-only.
• Gas emergency? Call the National Gas Emergency Service on 0800 111 999 (only if you smell gas or a CO alarm sounds).
• Smart Plan boiler cover is a service plan, not insurance: parts and labour up to £500 per 12-month period (boiler under 7 years) or £200 (over 7 years) — so a larger repair can exceed the cap and you pay the difference.
• A £95 call-out fee, paid in advance, applies in your first 30 days, for issues that aren't covered, for no-access visits, and for early annual-service requests.
• Cover is monthly and modular, but once you use a service a 12-month agreement period begins — leaving early costs the remaining months or 75% of the outstanding balance.

Why does the Baxi E110 code appear?

E110 fires when heat can't move away from the heat exchanger fast enough, so the temperature spikes past the safe limit and the thermostat trips. Almost always that comes down to poor circulation — the hot water isn't moving round the system the way it should.

Four causes account for most E110 faults. A jammed or failed pump means the heat simply isn't being circulated. Air trapped in the circuit creates pockets that stop water flowing freely. A blocked or scaled heat exchanger holds heat in one spot instead of carrying it away. And sludge — the black, gritty build-up that collects over years — restricts circulation throughout the system.

All four are internal faults on the water side of the boiler and heating system, which is why they're an engineer's job rather than something to tackle yourself. It's also why you shouldn't sit there resetting an overheat fault: the lockout is protecting the boiler, and clearing it again and again lets it keep running too hot without ever addressing the pump, blockage or air that caused it.

Baxi E110 causes at a glance

What can I safely do about a Baxi E110 fault?

Honestly, there's very little to try safely with E110, and the golden rule is that you must not keep resetting an overheat fault. There are only a couple of harmless checks worth doing before you call someone out — none of them involve opening the boiler.

1. Check the pressure gauge. It should read roughly 1.0 to 1.5 bar when the system is cold. If it's low, top it up once using the filling loop as shown in your boiler's manual.

2. If you're confident doing it, bleed your radiators to release trapped air — start with the ones cold at the top.

3. Make sure the radiator valves are open so water can circulate freely.

4. Then stop. If E110 is still showing after those checks, don't reset it again — book a Gas Safe registered engineer.

That's genuinely the limit of safe homeowner action here. A jammed pump, a blocked or scaled heat exchanger and system sludge are all internal jobs that only a qualified engineer should carry out. Repeatedly resetting an overheat lockout won't fix any of them — it just lets the boiler keep tripping while the underlying fault gets worse.

When to call a Gas Safe registered engineer for E110

Call an engineer straight away if E110 keeps showing after your basic pressure and air checks, or if it returns after a single reset. The pump, the heat exchanger and any system cleaning are all jobs for a Gas Safe registered engineer — it isn't work to attempt yourself, and you can check anyone you use is listed on the Gas Safe Register.

A pump, heat-exchanger or system-cleaning job — the usual culprits behind a recurring E110 — is a chargeable engineer visit, so ask your engineer to quote the work before it goes ahead.

If you'd rather spread the cost of future repairs, that's what an ongoing boiler module is for — but read the limits before you decide. Smart Plan is a service plan, not insurance. A boiler module covers parts and labour up to your cover limit — up to £500 per 12-month period if your boiler is under 7 years old, or up to £200 if it's older. Be realistic about that cap: a bigger job on an older boiler can run past the £200 limit, so you'd pay the difference on any shortfall. A £95 call-out fee, paid in advance, applies in your first 30 days, for issues that aren't covered, for no-access visits and for early annual-service requests. Cover-plan call-outs run Monday to Friday, 08:00 to 18:00 unless it's a genuine emergency, so for a non-emergency overheat lockout like E110 you'd usually get a weekday appointment rather than a weekend one. Cover is monthly and modular, but once you use a service a 12-month agreement period begins, and leaving early costs the remaining months or 75% of the outstanding balance. We've looked after over 15,000 customers and we're from UK Boiler Company Ltd, trading since 2014.

One safety note: E110 itself is an overheat lockout, not a gas emergency. But if you ever smell gas or your carbon monoxide alarm goes off, leave the boiler alone and call the National Gas Emergency Service on 0800 111 999 — open the windows, turn the gas off at the meter if you safely can, don't touch electrical switches, and get everyone out.

Baxi E110 fault FAQs

Seeing E110? Get a Gas Safe engineer booked.

Book a one-off repair and a Gas Safe registered engineer will look at it, or set up an ongoing Smart Plan boiler module so future faults are covered. It's a service plan, not insurance — parts and labour up to your cover limit (£500 per 12-month period under 7 years, £200 if older), so a larger repair can exceed the cap and you pay the difference. A £95 call-out fee, paid in advance, applies in your first 30 days, for excluded issues, no-access visits or early annual-service requests; call-outs run Monday to Friday, 08:00 to 18:00 unless it's a genuine emergency; and using a service starts a 12-month agreement period (early exit costs the remaining months or 75% of the balance). Call 0333 772 6247, Monday to Friday, 08:00 to 18:00.

Helpful links

• Baxi E133 gas supply fault
• Baxi E119 low pressure fault
• All Baxi boiler fault codes
• No heating? Book a repair
• Boiler & central heating cover
• Baxi error codes (manufacturer)
• Check an engineer on the Gas Safe Register