BoilerFaultCodesWhat the manual says
Manufacturer manualSafety switch-off: Temp. spread too large - Temperature spread too great. Water circulation too low
What causes this fault?
This fault occurs when the boiler's internal sensors detect that water is heating up too quickly or that there is a massive temperature difference between the pipes going out and coming back. The most common reason is a blockage or a failing pump preventing the water from circulating through your radiators. It essentially means the heat being generated has nowhere to go, so the boiler shuts down to prevent internal damage from overheating.
This fault is frequently seen at the start of autumn when heating systems are turned back on after being idle, as pump components can seize or sludge can settle during the summer months.
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.
Avoid the next call-out bill
A cover plan would handle faults like F.23: no call-out fees, no surprise bills.
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Related fault codes
All 148 fault codes on the ecoTEC Pro 28
Seeing a different code? Every code this model can display, in one place.