BoilerFaultCodesYour heat pump has stopped working because its internal system is getting too hot, usually due to a lack of water flow or a refrigerant issue.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Compressor Discharge Temperature High
What causes this fault?
This fault occurs when the gas leaving the compressor becomes dangerously hot, which usually happens because heat isn't being moved away from the unit quickly enough. The most common cause is restricted water flow through the system due to a failing pump or a blockage, but it can also be triggered if the unit is leaking refrigerant.
This fault is more common during summer heatwaves or periods of very high demand for hot water, as the system has to work harder to reject heat.
DIY fix possible
Check that all radiator valves and zone valves are fully openEnsure the external unit is clear of leaves, debris, or snow blocking airflowCheck your system pressure gauge and top up to 1.5 bar if it is too low
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A boiler cover plan would cover faults like P4 — 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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