BoilerFaultCodesYour boiler has shut down because it has either become too hot or detected that dangerous exhaust fumes are not escaping correctly through the chimney.
Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now — this fault can be dangerous if ignored.
Technical description: Overheat condition has occurred or Products Discharge Safety Device (TTB) has operated due to flue blockage.
What causes this fault?
This fault occurs when the boiler's internal temperature or flue gases exceed safe limits, triggering a safety shut-off to protect your home. The most common reasons are a failure in the pump preventing water from moving through the system or a blockage in the chimney preventing exhaust fumes from escaping.
This issue often arises during the first cold spell of autumn, when a pump that has been idle all summer fails to seize or move water correctly upon restart.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like Red LED (Illuminated) — no call-out fees, no surprises.
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Potterton Kingfisher MF 40-100 is discontinued — time for a new one?
Parts for discontinued models can be hard to find and expensive. A new A-rated boiler could save you money on both repairs and energy bills.
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