BoilerFaultCodesTechnical description
CTN2 > 97°C - pump will run
What causes this fault?
This fault occurs when the internal temperature of the water exceeds 97°C, triggering a safety shutdown to prevent damage. The most common cause is a failure in the circulation pump or a blockage in the heat exchanger, which prevents the heated water from moving away from the burner quickly enough. It can also be triggered by air trapped in the system or a faulty sensor providing an incorrect high temperature reading.
This issue often surfaces during the first cold spell of autumn when the heating is turned back on after months of inactivity, as pump components can seize during the summer.
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.