High Lockout
2$ on Remeha Quinta 115

Your boiler has shut down because it incorrectly detects that water returning to the unit is hotter than the water leaving it, which usually points to a sensor or circulation issue.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

Return temp > flow temp

What causes this fault?

This fault occurs when the boiler's internal computer receives conflicting information, suggesting that the water coming back from your radiators is hotter than the water it just heated up. The most common reasons are a faulty sensor sending incorrect data or a pump failure that has caused the water to stop moving or flow in the wrong direction. Because this defies the laws of physics for a working system, the boiler shuts down for safety.

This issue is more frequent in autumn when heating systems are first turned on after summer, as circulation pumps can become seized or stuck due to months of inactivity.

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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