BoilerFaultCodesWhat the manual says
Manufacturer manualFault: Underfloor heating contact. Underfloor heating contact open, sensor disconnected or defective
What causes this fault?
This fault occurs because a safety switch designed to protect your underfloor heating has detected that the water temperature is too high, causing it to cut power to the boiler. The most common reasons are a failed pump that isn't moving heat away quickly enough or a fault with the limit switch itself. It acts as a safety barrier to prevent the high heat from damaging your floor surfaces.
This fault is more common during the autumn and winter months when the underfloor heating is first switched on after being dormant all summer.
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.86: no call-out fees, no surprise bills.
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Related fault codes
All 170 fault codes on the ecoTEC Plus 635
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