Ok, checked terminal 4 this morning as advised. With water only, no feed. So, popped wire back on and moved on.
Now, although I thought the pump was running, it seems I may have been wrong - happy to say so if I am as well. I just popped the water only on and ran upstairs to hear the pump, but cannot hear it running. Popped back down and triggered the CH and the pump does indeed start. So, that moves us on to another aspect.....
The thermostat has been set to maximum in error. I asked she who must be obeyed to turn it all the way off the other day and thought that was done,. but no. It was all the way to max. Now, with just the HW on the rads started getting hot as usual, but I am now wondering if it is possible that the thermostat had anything to do with that? I cannot see how as (as far as I know) the thermostat simply tells the pump to switch on or off surely?
This may sound like a daft question, but is it possible that everything is wired up correctly, and the rads are simply getting hot under gravity?
EDIT:
Just tried again. HW nly on boost, CH off. No pump activation, thermostat to min. HW gets nice and hot BUT upstairs rads are hot too. Downstairs stay cold.
So, that suggests to me that in fact the electrical side is working correctly after all. But because of the layout of the plumbing, when the HW gets hot the top rads get hot too. The more I think about it, the more it makes sense as well.
If anyone can confirm my thoughts I would be very obliged. Let me give the system layout again:
Ground floor, back boiler, thermostat, programmer etc. 3 rads. First floor, 3 rads, HW cylinder, pump. Loft, two tanks - one for HW one for CH.
So, gravity HW with pumped CH.
When HW obly is set on, HW works but top rads get hot and that is because they are level with the HW cylinder. Does that sound about right?
Cheers
Dave