How much does it cost to fix Main error code 28?

Typical repair cost for the Main 28 fault is £90-160 including labour.

28 High

Main 28 Fault Code

Q: What does the Main 28 fault code mean?

Your boiler is having trouble measuring the temperature of your hot water, which usually means your taps and showers will only run cold.

The Main 28 fault code means: your boiler is having trouble measuring the temperature of your hot water, which usually means your taps and showers will only run cold.. It appears on 3 Main models in our database.

Technical description: Fault on Hot Water Sensor

Typical repair cost £90-160 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Main models that show the 28 fault code

Click a model for the full fault code list and model-specific repair notes.

Combi 30 HE Repair: £120-180
Ecoinstaller 2 Repair: £90-160
Insul 7 Repair: £80-150

Source

Main 28 fault code information on this page is sourced and cross-checked against the official Main service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026