Boiler not firing up when Heating Comes on.

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I have just replaced my old Horstmann 423 Diamond timer control with a new Horstmann 425 Channel Plus control.

The wiring diagram shows how to wire up for a two channel control.

I currently have it set so the heating comes on at a seperate time to the hotwater, this is different to how the old 423 worked, it was only a 1 channel control with both coming on and off at the same time.

When the heating comes on, it only switches the heating pump on. The boiler doesn't fire up.

What I want to know is, should the boiler automatically fire up when the pump starts, and the room thermostat then switches the pump and boiler on and off as the thermostat controls it?

Or... should the pump switch on and circulate the water, and the boiler only fire up when the heating water in the circuit drops below temperature?

 

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Note: I am working from the assumption that my system is the old Convection type, I can only see a pump on the radiator circuit, there doesnt appear to be a diversion valve (sorry not sure on its correct name) to make my system a fully pumped system.