vaillant 428 ecotec open vent bolier

[Jules3011]

I have noticed on occasions that the bolier shuts down for a period of time even though the room stat is calling for heat. The orange ,white and gray wires on the mid position v/v are live thus providing a live feed to the boiler . In this instance the boiler is not providing a live feed to the pump ., is this normal with this type of boiler or have I got an intermitant fault on the boiler.

[plumbbob]

No boiler will fire continuously when the heating is on. The boiler will shut down when the water temperature reaches the pre-set level. Once the water in the system cools as the radiators give out heat, the boiler will fire again to warm the water.