Ideal boiler shows L5 after power interruption or lockout, boiler unresponsive until reset

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

Possible Causes

Power cut during ignition sequence, Flame signal present when no flame, PCB sensing error, Faulty flame sensor

Safety first: Ensure the boiler is on a dedicated fused spur. Do not repeatedly reset a boiler that immediately locks out.

User steps:

Power cycle: Turn off the boiler at the fused spur for 30 seconds, then turn back on.
Reset: Press and hold the reset button as per the user manual (usually for a few seconds) until the boiler attempts to restart.
Observe: If the boiler runs normally afterwards, the L5 may have been caused by a brief power issue.

If L5 recurs frequently, a Gas Safe engineer should test the flame detection circuit and PCB.

Medium 3/5

PCB (Printed Circuit Board)

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