How to Fix the Baxi E28 Fault Code

A Baxi E28 fault code usually points to a problem with the flue thermistor or a frozen condensate pipe, both of which can stop your boiler from operating safely.

In some cases the fault is easy to resolve. In others, it needs professional diagnosis. This guide explains the common causes, the checks you can safely carry out, and when it's time to call a Gas Safe engineer.

What Does the Baxi E28 Fault Code Mean?

The E28 fault code is a safety lockout. It normally indicates one of these issues:

• A faulty flue thermistor that is sending incorrect temperature readings.
• A frozen condensate pipe preventing condensate from draining correctly.

The boiler shuts down to protect itself and your property. Although the fault can sometimes be straightforward, it should not be ignored.

If you're seeing a different error, our complete guide to Baxi boiler fault codes explains what each code means and the next steps.

Common Causes of the Baxi E28 Fault Code

• Faulty flue thermistor — incorrect temperature readings trigger the safety lockout.
• Frozen condensate pipe — ice blocks condensate from draining during cold weather.
• Control board fault — electronic faults can generate false error readings.
• Damaged wiring — loose or damaged wiring interrupts sensor signals.
• Low system pressure — a secondary, less common factor. E28 is primarily a flue thermistor or condensate fault; low pressure alone rarely triggers it directly, but it's occasionally listed as a contributing factor.

Should You Reset Your Boiler?

Resetting the boiler may clear a temporary fault, but it will not fix the underlying problem.

If the E28 code comes back after resetting, further checks are needed.

How to Fix the Baxi E28 Fault Code

Turn off the boiler

Switch the boiler off before carrying out any external checks.

Check the condensate pipe

During freezing weather, inspect the external condensate pipe for ice. If frozen:

• Wrap it with a warm towel.
• Use warm water to thaw the pipe.
• Avoid boiling water, as it can damage plastic pipework.

Restart the boiler once the pipe has thawed.

Inspect the flue

Check the external flue terminal for leaves, snow or debris that could restrict airflow. Do not dismantle the flue.

Reset the boiler

After completing the checks, reset the boiler following the manufacturer's instructions. If the fault returns, further investigation is required.

Faulty flue thermistor

A failed thermistor will normally require replacement. This involves working inside the boiler and should only be carried out by a Gas Safe registered engineer.

Call a professional

If the E28 fault remains after these checks, arrange a professional inspection. Internal wiring faults, PCB failures and sensor faults require specialist diagnosis.

Preventing Future E28 Faults

You can reduce the chance of the E28 fault returning by:

• Booking an annual boiler service.
• Insulating exposed condensate pipework.
• Keeping system pressure within the recommended range.
• Fixing minor faults before they develop into larger repairs.

Need Help with a Baxi E28 Fault?

If your Baxi boiler still displays the E28 fault code after basic checks, don't keep resetting it.

A qualified Gas Safe engineer can identify the cause and carry out the repair safely. If the fault won't clear or keeps returning, book a professional Baxi boiler repair with one of our Gas Safe engineers.