Why does the boiler switch on and off repeatedly?

This situation can occur when installing thermostatic control heads that operate by modulating the flow rate, as in the case of the Comfort Control electronic controls. A differential by-pass is therefore necessary as it ensures the minimum flow rate required by the boiler to prevent it from switching off repeatedly. Boilers often already have it installed, so all you need to do is open it to adapt the boiler to a thermostatic regulation system.