BoilerFaultCodesTechnical description
High-temperature difference
What causes this fault?
This fault occurs when the water inside the boiler heats up too quickly because it isn't being moved away into your radiators fast enough. The most common reasons are a failing external pump, a blockage in the pipework, or a buildup of debris and limescale inside the heat exchanger that restricts water flow.
This issue often surfaces in autumn when the heating is turned back on after a long summer break, as external pumps can seize up during periods of inactivity.
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 →