A Baxi E20 means the central heating temperature sensor on the flow pipe, or the wiring to it, has failed, so the boiler can’t tell how hot the water is and stops. A worn-out sensor is the usual culprit, followed by a corroded connector, water in the wiring and, now and then, the PCB. If your Baxi is an older one showing E20, a new Baxi boiler is usually the better route for long-term efficiency and fewer repair bills.
We’re Clever Energy Boilers, Gas Safe registered (no. 554138) and based in Bingley. We’re also accredited Worcester Bosch installers, fitting new boilers across Yorkshire, the North West and the Midlands, and we’ve completed more than 25,000 installations in the last 15 years. On its own, E20 is one of the cheaper Baxi repairs. This page covers what the code means, the E02 mix-up to rule out first, what a fix costs and when the boiler’s age makes replacement the better call.
What does the Baxi E20 error code mean?
Baxi lists E20 as a “central heating NTC fault”. An NTC is a thermistor, a small sensor whose resistance changes with temperature, and this one sits on the flow pipe where hot water leaves the boiler for your radiators. When the sensor or its wiring fails, the boiler loses its flow temperature reading and locks out.
The meaning is the same on the Platinum Combi, Duo-tec, Main Eco, EcoBlue Advance, Assure and the original 600 and 800 Combi. Baxi classes it as a faulty component that the owner can’t fix. Newer Baxis use dotted codes, and there the equivalents are E.04.01 and E.04.02, which flag a flow sensor that’s gone short circuit or open circuit.
Before going any further, check the display really says E20. On the 200 and 400 Combi, E.02.07 means low pressure, and read quickly, “E02” looks a lot like “E20”. If yours shows E02 07, you’ve got a pressure problem rather than a sensor fault, and our guides to the Baxi H.02.07 error code and the Baxi E119 fault code cover low pressure in full.
Why is my Baxi boiler showing an E20 fault?
The causes, most likely first:
- A failed NTC sensor. The thermistor wears out or breaks down. This is the most common reason.
- A corroded or loose connector. The plug on the sensor, or the loom running back to the board, can corrode or work loose over time.
- Water in the wiring. A drip inside the casing can reach the sensor connection and upset the reading.
- The PCB, occasionally. If the sensor and wiring test fine, the board may be misreading it, and our guide to boiler PCB faults explains how that happens.
Damp air doesn’t help a connector that’s already corroding. Plenty of older terraces in Bradford and Halifax have the boiler down in the cellar, so if yours is one of them, mention it to the engineer.
Is the Baxi E20 fault dangerous?
No. The boiler has shut down because it can’t read the water temperature, which is the safe thing to do, and the code itself carries no gas risk. As with any boiler, if you smell gas, turn it off at the meter, open the windows and call the National Gas Emergency Service on 0800 111 999.
What can I safely check at home when my Baxi shows E20?
Nothing at home will fix a failed sensor. These are the steps worth taking:
- Read the display carefully. Make sure it says E20 and not E02 07. If it’s the pressure code, top up to 1 to 1.5 bar using our guide on how to repressurise a boiler.
- Reset or power cycle once. Hold the reset (R) button for 5 seconds, or switch off at the fused spur for a minute and back on.
- Look for drips. Water under the boiler is worth mentioning to the engineer, because it may have reached the wiring.
If E20 comes back, leave the casing on. The sensor sits inside the boiler and needs a Gas Safe registered engineer.
When should I stop resetting the E20 error and get a Gas Safe engineer?
Straight after one failed reset, since more resets won’t bring a dead sensor back. An engineer will test the sensor’s resistance (they expect around 10k ohms when it’s cold), check the connector and wiring for corrosion, and replace whichever part has failed.
Why does the Baxi E20 fault code keep coming back?
Usually the sensor is on its way out and only works some of the time, or a corroded connector is making and breaking contact. If the code returns after a new sensor has gone in, the wiring loom or the board is next in line.
On an older boiler it often arrives alongside wiring corrosion and other wear.
Is an E20 error a sign you need a new Baxi boiler?
Not by itself. A sensor swap is one of the cheaper Baxi repairs, and on a boiler a few years old it’s the sensible fix. Typical UK costs:
| Baxi E20 repair | Typical UK cost |
|---|---|
| NTC sensor test and replacement, fitted | £100 to £180 |
| Engineer labour, if more work is needed | £50 to £80 per hour |
| Replacement PCB, if the board is at fault | About £300 |
Source: MyJobQuote, October 2026.
The case for replacing rests on age and history. The Baxis that show E20 as a classic E-code, like the Duo-tec, Platinum and EcoBlue, are now roughly 10 to 18 years old. On a unit over 8 years old, an E20 often signals corrosion and wear elsewhere, and one call-out tends to lead to another. If you’ve had several faults this year, our guide on when a boiler needs replacing will help you decide, and new boiler costs shows what a replacement involves.
Get a new Baxi boiler with Clever Energy
We install Baxi boilers across Bingley, Keighley, Bradford, Halifax, Leeds and the wider Yorkshire area, as well as the North West and the Midlands. Our team is Gas Safe registered, new boilers come with the option of a long, market-leading warranty through Clever Energy, and boiler finance is there if you’d rather pay monthly. Take a look at our Baxi boiler installation service, get your fixed online boiler quote, or request a callback. If you’d rather talk it through, call 0330 055 2210 between 8am and 8pm on weekdays or 10am to 4pm at weekends.
Baxi E20 fault code FAQs
What does E20 mean on a Baxi boiler?
It’s a central heating NTC fault. The flow temperature sensor or its wiring has failed, so the boiler can’t read the water temperature.
Can I reset a Baxi E20 fault?
Yes, once. If E20 comes back, the sensor needs testing by a Gas Safe registered engineer, and Baxi says it isn’t something owners can fix.
Is the Baxi E20 fault expensive to fix?
Usually not. A new sensor typically costs £100 to £180 fitted, and it only gets pricier if the wiring loom or PCB turns out to be the problem.
Will my Baxi still give hot water with an E20 fault?
Don’t count on it. Baxi treats E20 as a faulty component that needs an engineer, so plan for the boiler being out of action until the sensor’s checked.
Can low pressure cause a Baxi E20 error?
No. E20 is a sensor fault. Low pressure shows as E119 or 118 on older models and H.02.07 on newer ones, and E02 07 on the display is the pressure code, not E20.
More Baxi error codes
Before this one in our set is the Baxi E119 fault code for low pressure. Next, the Baxi E1 error code guide explains how to read any E1 code with two more digits after it. If your Baxi has also been overheating, the Baxi E110 fault code is a useful read.
The E125 circulation fault, the E133 gas and ignition fault, the E160 fan fault and the E168 code all have their own pages, and the whole list is on our Baxi boiler error codes guide.