BoilerFaultCodesTechnical description
Variation on temperature of primary and/or return too high
What causes this fault?
This fault occurs when the boiler detects that heat isn't being carried away from the burner quickly enough, causing a sudden, unsafe rise in temperature. The most common reasons are a pump that has seized or failed, a blockage in the internal pipework, or a buildup of limescale and sludge that restricts the flow of water.
This issue often appears when the heating is first turned on in autumn, as pumps can seize up after being inactive throughout the summer months.
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 →