BoilerFaultCodesTechnical description
error – incorrect HCM fitted
What causes this fault?
This fault occurs when the boiler's main control board cannot communicate with the small data chip that identifies the specific model and power output. The most common reason is that this chip has worked loose from its socket, or it has been replaced with a version that is incompatible with the rest of the components. Because the system doesn't know exactly which model it is, it shuts down as a safety precaution to prevent incorrect operation.
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.
Find a Gas Safe engineer
Search the official register →