Protherm Short Cycling / Unstable Operation

Boiler starts but shuts down after a few seconds without showing an error code

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

Oversized boiler relative to system, Incorrect minimum output setting, Faulty temperature sensor causing premature shutdown, Poor circulation or blocked bypass

How to Fix / Troubleshooting

Safety: Isolate power and gas before internal checks.

Steps:

Ensure all radiators and circuits are open to provide sufficient load.
Check system pressure and bleed air to improve circulation.
A technician can adjust boiler parameters (minimum output, pump overrun) via the service menu to reduce short cycling.
Test NTC sensors for correct readings and replace if faulty.
Verify that any automatic bypass valve is correctly set and not fully closed.

Repair Difficulty

Hard 4/5

Required Part

Automatic Bypass Valve

Check Price on Amazon

We may earn a commission from links on this page.