BoilerFaultCodesTechnical description
Heat exchanger temperature too high (Tset + 5K)
What causes this fault?
This fault occurs when the water inside the boiler heats up much faster than the system can carry it away, causing it to reach a dangerous temperature in seconds. The most common reasons are a pump that has stopped working or a buildup of sludge and debris that is physically blocking the flow of water through the narrow channels of the heat exchanger.
This issue often surfaces during the first cold spell of autumn when a pump that has been idle all summer fails to restart or struggles to push through settled debris.
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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