Error code
Baxi Boiler Error Code E28
Baxi E28 is model-dependent. Baxi's technical table lists it as a flue NTC sensor fault for several boiler ranges, while Baxi homeowner guidance also says E28 can appear when a condensate pipe freezes. Check the exact model manual and symptoms before assuming one cause, and keep all checks outside the casing.
Quick answer
E28: A model-dependent warning linked to the flue temperature sensor or, on some boilers, frozen condensate
Meaning
A model-dependent warning linked to the flue temperature sensor or, on some boilers, frozen condensate
First safe check
Record the full model name and the exact displayed code before resetting anything.
Stop if
E28 returns after one permitted restart
Who to call
Contact a Gas Safe registered engineer if E28 appears without an obvious frozen external condensate pipe, returns after one permitted restart, occurs in mild weather, or requires sensor, wiring, flue, combustion, or casing access.
High severity: escalate quickly if it persists. Keep checks outside the casing and use only a manufacturer-approved reset where the manual allows it.
Fix time
A few minutes to identify the model and check external cold-weather symptoms
Difficulty
Professional-only unless an external condensate pipe is visibly frozen
E28 must be matched to the exact model and symptoms before choosing a response.
Expected outcome: A frozen external condensate pipe may clear using Baxi's homeowner method; flue NTC or repeated faults need qualified diagnosis.
What does this error code mean?
Baxi uses E28 differently across boiler families. Its professional error-code table lists E28 as a flue NTC temperature-sensor short-circuit or open-circuit fault for several compact, combi, and system ranges. That route needs qualified diagnosis because the sensor, wiring, flue, and combustion areas are inside the appliance.
Baxi's homeowner cold-weather guidance also says E28 can appear on some boilers when the external condensate pipe freezes. If the weather is freezing, the boiler is making a gurgling sound, and the accessible outside condensate pipe is visibly frozen, follow only Baxi's external thawing guidance. Otherwise treat E28 as a model-specific internal fault and arrange professional help.
The flue NTC monitors flue-gas temperature on supported boiler ranges and sits inside the appliance. Frozen condensate is a separate external cold-weather condition documented by Baxi for some boilers that can also present with E28.
Symptoms users may notice
- The boiler may lock out and stop heating or hot water.
- In freezing weather, a frozen condensate condition may be accompanied by gurgling and an iced external pipe.
- A flue NTC fault may return without any visible external condensate blockage.
What users often notice
- Search results often present one universal E28 meaning, but Baxi's own material shows that the interpretation depends on boiler range and circumstances.
- The weather, exact model, and whether the external condensate pipe is visibly frozen are important clues.
Why is this happening?
- Flue NTC temperature sensor open-circuit or short-circuit on supported Baxi ranges
- Sensor wiring or connection fault requiring internal diagnosis
- Frozen external condensate pipe on some boilers during freezing weather
- A different model-specific condition defined in the exact boiler manual
What this usually points to
The flue NTC monitors flue-gas temperature on supported boiler ranges and sits inside the appliance. Frozen condensate is a separate external cold-weather condition documented by Baxi for some boilers that can also present with E28.
How to fix this safely
- Record the full model name and the exact displayed code before resetting anything.
- Check for a smell of gas, overheating, leaking, electrical concern, or repeated lockout; stop immediately if any is present.
- In freezing weather only, inspect the accessible external condensate pipe for an obvious frozen section without opening the boiler casing.
- If the pipe is visibly frozen, follow Baxi's homeowner method using a hot-water bottle, heat pack, or warm but not boiling water, while taking care of slippery runoff.
- If there is no obvious frozen external pipe, or E28 returns after one manufacturer-approved restart, arrange a Gas Safe registered engineer.
Can I fix this myself?
MaybeThe only homeowner fix described by Baxi is thawing an obviously frozen, accessible external condensate pipe in cold weather. Flue-sensor, wiring, and internal causes are professional-only.
Safety boundary: Do not remove the casing, touch flue or combustion components, test internal sensors, or pour boiling water on a condensate pipe.
What not to do
- Do not remove the boiler casing or test the flue NTC sensor or wiring.
- Do not use boiling water, a naked flame, or an unsafe heat source on a condensate pipe.
- Do not keep resetting a boiler that repeatedly locks out.
Common misdiagnoses
- E28 is sometimes described only as frozen condensate, but Baxi's technical table also uses it for a flue NTC sensor fault on several ranges.
- A sensor fault should not be treated as a DIY condensate problem without the exact model and supporting cold-weather symptoms.
Reset steps
- Use the exact model manual to find the permitted restart or reset method.
- Try one restart only after an obvious external frozen-condensate condition has been safely cleared and there is no other safety concern.
- If E28 returns, stop resetting and contact a Gas Safe registered engineer.
Intermittent vs persistent faults
An E28 caused by an external frozen condensate pipe may clear once the pipe is safely thawed. E28 that returns, appears in mild weather, or has no obvious external blockage should be treated as a persistent professional fault.
Manual reference
Baxi boiler error-code table and exact model manualCountry safety notes
UK
Gas boiler work should be carried out by a Gas Safe registered engineer.
When to call a heating professional
Contact a Gas Safe registered engineer if E28 appears without an obvious frozen external condensate pipe, returns after one permitted restart, occurs in mild weather, or requires sensor, wiring, flue, combustion, or casing access.
Safety warning
Do not open the boiler casing or work on gas, combustion, flue, sensor, or internal electrical components. In the UK, use a Gas Safe registered engineer for gas-boiler work.
Useful hub links
Related fan and flue fault codes
Relevant guide
Frequently asked questions
What does Baxi boiler error code E28 mean?+
It depends on the boiler. Baxi lists E28 as a flue NTC sensor fault for several ranges, while its cold-weather guidance says E28 can also appear with frozen condensate on some boilers.
Can a frozen condensate pipe cause Baxi E28?+
Yes, on some Baxi boilers. Look for freezing weather, gurgling, and an obviously frozen accessible external pipe, then follow Baxi's external thawing guidance only.
Can I fix a Baxi flue NTC fault myself?+
No. Flue-sensor, wiring, combustion, and internal boiler work require qualified professional diagnosis.
Should I keep resetting Baxi E28?+
No. Use only one manufacturer-approved restart after a safe external cause has been cleared. If E28 returns, arrange professional help.
Sources and review status
Model dependent · Last reviewed 14 July 2026
- Baxi professional boiler error-code table
manufacturer support · UK · checked 14 July 2026
Baxi lists E28 as a flue NTC sensor short-circuit or open-circuit fault for several compact, combi, and system boiler ranges.
- Baxi homeowner guide to thawing a frozen condensate pipe
manufacturer support · UK · checked 14 July 2026
Baxi says E28 can appear on some boilers when the condensate pipe is frozen and provides an external homeowner thawing method.
- HSE domestic gas safety guidance
government safety · UK · checked 14 July 2026
HSE guidance confirms that domestic gas-appliance work should be carried out by a competent Gas Safe registered engineer in the UK.
Model variation note
Baxi E28 is not a single universal diagnosis. Baxi's professional table lists a flue NTC sensor fault for several ranges, while its homeowner cold-weather guidance associates E28 with frozen condensate on some boilers. Confirm the exact model manual.