BoilerFaultCodesYour boiler has detected that the water inside the main heating unit has frozen, which is preventing the system from operating to avoid damage.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Main heat exchanger frozen
What causes this fault?
This fault occurs when the temperature sensor inside the boiler detects that the water within the heat exchanger has reached freezing point. The most common cause is the boiler being located in an unheated area like a garage or loft during a cold snap without adequate frost protection. It can also be triggered if the external condensate drainage pipe reflects a blockage caused by ice, preventing the system from circulating safely.
This fault is almost exclusively seen during the winter months when external temperatures drop below freezing for extended periods.
DIY fix possible
Check if the condensate pipe (the plastic pipe leading outside) is frozen and thaw it with warm water or a heat pack.Increase the room thermostat temperature and wait for the ambient heat inside the house to naturally thaw the unit.Reset the boiler once the system has thawed completely.
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