BoilerFaultCodesTechnical description
Maximum delta temperature (flow - return). Water circulation fault. Check central heating flow and return connection
What causes this fault?
This fault occurs when the boiler's internal sensors detect that heat isn't being carried away from the burner fast enough, causing the unit to overheat rapidly. The most common reason is a blockage in the system or a pump failure, which prevents water from circulating through the radiators as it should.
This issue often surfaces during the first cold snap of autumn when heating systems are turned on after sitting idle for months, which can cause internal pumps to seize.
Engineer required
This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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