BoilerFaultCodesYour boiler has detected that a safety device designed to prevent water overflow or blockages has been triggered, causing the system to shut down.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: The diagnostics will indicate the nature of the fault to assist a speedy and effective repair
What causes this fault?
This fault occurs when water backs up within the system because it cannot drain away properly, triggering the safety float switch to cut off the boiler. The most common reasons are a blockage in the internal condensate trap, a buildup of debris in the drain pipe, or a failure of the external pump that moves wastewater away from the unit.
This fault is more common during freezing winter temperatures, as the external condensate pipe can freeze solid, causing water to back up into the boiler and trigger the switch.
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 Float switch (if fitted) — no call-out fees, no surprises.
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Ideal Concord CXA 40-120 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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