W-plan pump run on

[John.g]

convert from the existing W plan...
If I changed it to S plan, when both are satisfied there would be nowhere for the residual heat to circulate ....as mentioned, the bypass loop appears to be just that - a 15mm pipe around the pump which I am not sure IS a bypass loop as such
"only" CH or HW is fine as it is quite a small house and the HW requirement is low

You could go the conventionel way of installing a ABV between the boiler flow&return if converting to a S plan otherwise convert to a W system with a 3 port diverter valve.

 

[davidwf]

possibly..... just possibly.......
I suggested he turned the CH stat right down and turned the HW stat right up......popped over to the house this morning and found the rads were red hot.
Investigation found that the valve was not returning fully to the home position when the CH satisfied (W-plan remember)……there was no voltage across the motor so nothing could be holding it open
I undid the 2 screws that hold the backplate to the brass valve about 1/2 a turn and the assembly immediately fully opened which should of course close the CH circuit…….did them back up and operated it again and it was quite stiff and didnt return fully…..
I have put two small washers between the backplate and the brass valve to space it out a little bit and it now APPEARS to be working properly !.....hmmm
...and that was a brand new unused Honeywell V4044C1288/U 22mm 3 Port motorised diverter valve, sadly bought off a private seller on ebay so no guarantee, the backplate looks straight and there are no dents or anything anywhere

If it continues to work OK I will take that as a win

 

[davidwf]

You could go the conventionel way of installing a ABV between the boiler flow&return if converting to a S plan otherwise convert to a W system with a 3 port diverter valve.

it already IS (and always has been) a W-plan system with motorised diverter valve..........