Central Heating checks

[efiste2]

Our CH system has been installed for a couple of years now, since then I have always thought that the tank stat wasn't working as it should as adjusting it never really affected the temp of the water. However I never got round to checking it out properly.
Last week I came in from work to a warm house, and turned the stat down, I was expecting the heating system to go off, or just the pump. But as far as I can tell neither did as I could still hear the boiler working and the pump working ( I could still hear the whooshing sound the hall rad makes when it's on)
Bringing the two together I'd like to check the switching of the system so to speak, the system is a sealed pumped CH HW System with a Worcester Bosch Greenstar 24i Boiler. The system has a large terminal block which all the cables terminate in. Having some electrical knowledge, is it feasible for me to check that the switching is working correctly at the block. Ie with the system on, adjust the stat up and down to see if i get a switch on and off signal, and do the same with the HW tank stat.
Of course I'm assuming that turning the stat right down should turn the boiler and pump off at once , is this actually the case, or is there a run down time or something similar.
I hope this makes a little sense and appreciate any advice

 

[Terry lambert]

This boiler should have a pu,p over run, so the pump will keep running to dissipate heat after a demand for a few minutes

What type of system do you have? S plan, Y plan or something else

 

[efiste2]

I think its a Y Plan, it has a Three position valve and no other valves anywhere else. Thanks so much for the advice, the running on setting makes sense