High
H 4 on Ideal Icos HE

Your boiler has detected an internal communication error, meaning it has shut down to prevent potential damage to its main control system.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

FAULT FINDING CHART MAIN MENU CODE - GO TO FRAME 68

Engineer required

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

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