BoilerFaultCodesTechnical description
Installation accessories- Communication with variable speed pump (low voltage HM)
What causes this fault?
This fault occurs when the boiler's main control board loses its digital connection with the internal circulation pump. The most common reason is a hardware failure within the pump’s electronic motor head or a loose communication cable, meaning the boiler can no longer control the speed of the water flow. Without this connection, the system shuts down as a safety precaution to prevent the heat exchanger from overheating.
This fault is more common in autumn when the boiler is switched back on after being idle all summer, which can cause internal pump components to seize or fail.
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.