BoilerFaultCodesTechnical description
Boiler max temperature exceeded for gradient (probable pump jammed or air in the circuitBoiler max temperature exceeded for overtemperature (probable pump jammed or air in the circuitSafety thermostat sensor tripped.
What causes this fault?
This fault occurs when the water inside the boiler heats up so quickly that the safety sensors shut the system down to prevent damage. The most common cause is a blockage or a failed pump preventing water from moving through the pipes, but it can also be triggered by large air bubbles trapped within the unit.
This issue is more frequent in autumn when heating systems are switched back on after a summer of inactivity, which can cause the internal pump to seize or get stuck.
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.