Boiler Overheating and Locking Out
The boiler runs hot for a minute or two, then shuts down on a fault before the room reaches temperature..
The boiler runs hot for a minute or two, then shuts down on a fault before the room reaches temperature.
What is actually going on
The boiler runs hot for a minute or two, then shuts down on a fault before the room reaches temperature.
The realistic causes, in order
Poor circulation from a blocked heat exchanger, a sludged system or a partially closed valve, so heat can't leave the boiler A pump running too slowly, or set to a head that no longer suits the system after radiators were added A failed overheat thermostat or flow sensor reading high when the water isn't actually that hot
What we test on site
Flow and return temperature differential across the boiler under load — a wide split points at circulation Pump performance and speed setting against the system's actual resistance System water quality, magnetite content and filter condition
Questions we get asked
What causes an overheat lockout on a gas boiler?
Poor circulation from a blocked heat exchanger, a sludged system or a partially closed valve, so heat can't leave the boiler
What normally puts an overheat lockout right?
Fixing circulation usually means a filter, a flush or a valve correction — cheaper than the boiler damage that follows if it's ignored.
Is it safe to keep using the system with an overheat lockout?
Repeated overheat lockouts should not be reset again and again. The lockout is doing its job; the underlying circulation fault is what needs fixing.