BoilerFaultCodesYour boiler is heating up too quickly when you turn the tap on, which usually means water isn't flowing through the system fast enough to take the heat away.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Temporary error – flow temperature increasing too fast in domestic hot water (DHW) mode, insufficient circulation or sensor error.
What causes this fault?
This fault occurs when the water inside your boiler heats up much faster than the system expects, causing it to shut down to prevent overheating. The most common reasons are a blockage in the internal heat exchanger or a pump that isn't able to push the hot water away from the burner quickly enough. It can also be caused by a faulty sensor giving the boiler an incorrect temperature reading.
This fault is slightly more common in summer when the boiler has been idle for long periods, which can lead to the internal pump sticking or debris settling in the heat exchanger.
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.
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A boiler cover plan would cover faults like H.01 – .21 — no call-out fees, no surprises.
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Could it be time for a new boiler?
If repair costs are adding up, a new energy-efficient boiler could be the smarter long-term choice.
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