BoilerFaultCodesTechnical description
Check system. Replace o/h stat. Press O/H reset button.
What causes this fault?
This fault occurs when the water temperature inside the boiler exceeds a safe limit, causing the safety sensors to shut the unit down to prevent damage. The most common reasons include a failing system pump that isn't moving water away from the heat exchanger fast enough or a buildup of sludge and debris that has restricted the flow of water.
This fault often occurs during the first few cold days of autumn when a heating system that has been dormant all summer is suddenly forced to work at high capacity.
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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