What does the Biasi E04 fault code mean?

Your boiler has detected that water isn't moving through the system quickly enough, causing it to overheat and shut down for safety.

How much does it cost to fix Biasi error code E04?

Typical repair cost for the Biasi E04 fault is £100-£350 including labour.

Check that the boiler pressure is between 1.0 and 1.5 bar on the gauge

Water circulation failure / High temperature gradient

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

Each noise points to a different fault.

Sludge build-up — needs flushing, not bleeding.

Lockout fault with a reset-needed pattern.