When should the pump work on a central heating system

[lenphy]

Up to this weekend when our oil fueled boiler fired up the circulating pump came on. Once up to temperature boiler and pump switched off.

When the timer switches on the central heating system now the pump runs continuously.

What is the likely cause of this problem?

Any help would be appreciated.

 

[jackthom]

Depends on whether the pump is wired directly into the boiler PCB and is controlled by it, or the pump is switched on/off by the heating controls, motorised valves etc.

 

[MANDATE]

I think you'll have to find out more about your system.
For example my room stat controls the pump only, but the boiler itself has a 'boiler stat' which allows the boiler to operate for the gravity HW.

In some systems the pump is used for both HW and CH and the power to drive the boiler and pump comes from two different sources. It will involve the cylinder stat where HW is involved and a motorised valve as well as a room stat for the CH part.
Just based on the basic information given I'd be looking to see if the room stat is operating. Sounds as though it may not be switching off when temperature is reached. Do you hear it click when turned up and down by hand