BoilerFaultCodesTechnical description
Safety switch off temperature limiter
What causes this fault?
This fault occurs when the boiler's internal heat exchanger reaches an unsafe temperature, forcing the system to shut down to prevent damage. The most common reasons are a lack of water flow caused by a broken internal pump, or a blockage in the pipes resulting from a build-up of sludge and debris.
This fault is more common when turning your heating back on for the first time in autumn, as circulation pumps can seize up after sitting idle during 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 →