Boiler displays A13, burner shuts down and restarts frequently (short cycling)

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

Insufficient system flow, Stuck or undersized bypass valve, Pump speed incorrectly set, Blocked system filter

Safety: Allow system to cool before adjusting valves or filters.

Steps:

Ensure all radiator valves and zone valves are open to provide adequate flow.
Check that the automatic bypass valve (if fitted externally) is correctly adjusted and not fully closed.
Clean the system filter or magnetic filter on the return line.
Adjust the pump speed on the IVT boiler (if variable) to a higher setting to improve circulation.
If A13 persists, a technician should check pipe sizing, balancing, and delta-T across the boiler and system.

Medium 3/5

Automatic Bypass Valve

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