OK, I've followed your instructions!
turn the roomstat down
turn the cylynder stat up
turn off HW and CH at the programmer and at the boiler spur
check that the mid position valve is at its rest (hot Water)position
now
Yep - valve at HW (top) position
1) turn on the spur and select hot water only
does the boiler fire and does the valve stay where it is?
Yes
2)while you are there checking the valve position turn down the cylinder stat
does the boiler go out and does the valve stay where it is?
Couldn't test this as water didn't come up to temp whilst I was there
3)now turn the cylinder stat back up to fire the boiler again and select CH on at the programmer (leave the HW switched on and the room stat down)
is boiler the boiler still firing and is the valve still in the hot water position?
Yes to both
Additionally, when turning the room stat up, the valve moves to the mid position (as it should, I guess).
One other thing I noticed, after turning CH and HW off at the boiler, the pump continued to run for a couple of minutes before stopping.
Matt
As regards the actual wiring, the pump is definitely connected to the orange valve wire. The junction box in the airing cupboard has nine connecting blocks, as per the photos I posted before.
As far as I can make out, the connections to each one is as follows :
1) Common earth
2) Red from room stat, yellow (middle cable)
3) White from 3-port valve, yellow from room stat
4) Common Neutral (Blue wires)
5) Orange from valve, Brown from Pump, Red (Top cable)
6) Earth, Yellow (Top cable)
7) Blue (top cable), Black from tank stat
8 ) Brown from tank stat, Red (middle cable)
9) Grey from Valve, Black from tank stat
The "top" and "middle" cables go into the wall, and I'm not sure to what they connect. One must go to the boiler, but perhaps they both do?
The top cable has Yellow, Red and Blue wires, the middle cable has Red, Yellow and Earth wires.