CH4, thanks very much for the last post - now feel like I have a much better understanding.
Honest this is final query.
Whole system seems to work as you have indicated, other than voltage at Grey wire when DHW is on only - this reads 150V approx ?? ( but I am not sure if I checked this...
CH4 thanks very much for that, think I'm getting out of my depth but it will help if I now call in engineer.
I checked this morning and noticed something a little strange.
1. If I advance the CH off, leaving HW on the valve return and shuts off flow to radiators.
2. If I reduce room...
Have ideal classic boiler and having problems with 3A fuse blowing in fused spur. After heating goes off can see that motor on valve ( diverter valve ? next to system pump in tank cupboard ) is not returning - so valve held open. If I turn power off at fused spur can see that valve returns, If I...