Boiler intermittently locks out with A13, especially at high heating demand, radiators may be only lukewarm.

Safety Warning

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

Faulty return NTC sensor, Poor circulation causing high temperature difference between flow and return, Blocked system filters or sludge, Pump running at too low speed

How to Fix / Troubleshooting

Safety: Isolate power before removing covers.

Check system filters: If a magnetic filter or Y-strainer is installed on the return, clean it to restore flow.
Open radiator valves: Ensure enough radiators are open to allow proper return flow.
Technician – test return NTC: Measure resistance of the Beretta return temperature sensor and compare to specification. Replace if faulty.
Technician – pump and system balance: Increase pump speed if appropriate and balance radiators to improve return temperature.

Repair Difficulty

Medium 3/5

Required Part

Return NTC Sensor

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