BoilerFaultCodesTechnical description
Overheat (With V9 Primary Control PCB, will display 3 horizontal lines upon reset and not refire until temperature drops below 50oC)
What causes this fault?
This fault occurs when the water inside the boiler exceeds a safe temperature, triggering a safety sensor to cut the power. The most common reasons are a pump failure that stops water from moving or a blockage within the main heat exchanger that prevents heat from transferring correctly. It can also be caused by air trapped in the system or a faulty sensor providing an incorrect reading.
This fault is frequently seen at the start of autumn when heating systems are switched back on after being idle, as circulation pumps can become seized over 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.