E28 on a Baxi is a flue NTC sensor fault, either a short circuit or an open circuit.

This one matters more than a heating sensor fault, because the flue sensor is part of how the boiler knows combustion is behaving.

What E28 actually means

The flue sensor monitors flue gas temperature. An unusually high flue temperature can indicate a blocked or failing heat exchanger, so the boiler watches it closely.

If the sensor reading is impossible, short circuit or open circuit, the boiler loses that protection and shuts down rather than run without it.

What you can safely check yourself

Nothing useful inside the appliance.

If the boiler has been running noisily, or the flue terminal outside has been steaming much more than usual, mention it, because a genuinely high flue temperature and a faulty sensor look different to an engineer.

When to stop, and why

What causes it beyond the simple checks

A failed sensor, a corroded or disconnected connector, damaged wiring, or a board input fault. Because a blocked heat exchanger can drive flue temperatures up, an engineer will want to establish whether the sensor is faulty or was reporting something real.

How Vantage can help

We are Gas Safe registered under 956889 and cover Hertfordshire, Bedfordshire and Cambridgeshire, with an emergency line answered 24 hours a day. Call us on 01462 506374. See also boiler repair and boiler servicing.

Frequently asked questions

Is E28 dangerous?

The boiler has stopped, which is the safe outcome. The reason it lost the flue reading needs establishing.

Could it mean my heat exchanger is blocked?

That is one of the things an engineer will rule out, because a genuinely high flue temperature points that way.

Is it an expensive fix?

A sensor is a modest part. A blocked heat exchanger is a different conversation, which is why it gets checked properly.

Related fault codes

Other Baxi codes: E09 · E10 · E20 · E110 · E119 · E125 · E128 · E133 · E160 · all boiler advice. See also boiler repair.

In Baxi’s own words

Baxi use different code sets across their ranges and generations. The definition above comes from The Baxi error code table. If your boiler is a different model and the code behaves differently, check the manual for your appliance or ring us and we will tell you what it means on your unit.

When to call an engineer

If the checks above have not cleared it, the next steps are engineer work and the boiler should not be reset repeatedly in the meantime. Call Vantage Plumbing and Heating on 01462 506374. We are Gas Safe registered under 956889, the line is answered by a person at any hour of any day, and you get a price before anyone starts.

Need help today?

Call and speak to a person, any hour, any day of the year. Get a fixed price quote or call 01462 506374.