BoilerFaultCodesWhat the manual says
Manufacturer manualFlow temperature too high, or
What causes this fault?
This fault occurs when the water leaving the boiler exceeds its safe temperature limit, causing the system to shut down for safety. The most common reasons are a pump failure that stops water from moving through the unit or a buildup of sludge and limescale that blocks the internal heat exchanger.
This fault is more common when the heating is first switched on in autumn, as circulation pumps can seize up after being inactive over 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.
Avoid the next call-out bill
A cover plan would handle faults like AL79: no call-out fees, no surprise bills.
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