THE WORKINGS OF A PUMPED C/H SYSTEM AND AGRAVITY FED H/W?

probably air locked of some sort. assuming you exchanged components that were there in the first place and not adding bits for fun?! bleed anything u can and run the heating/water with the pump on minimum speed until it sounds quiet then build to speed2-3.

gilo bg
September 2009

doesn't sound like it's a gravity hot water system.
if it is it shouldn't have a zone valve and the pump shouldn't operate when on hot water only.
for gravity h/w & pumped ch you would generally have 28mm flow and return pipes (may be 22mm) going to the cylinder then the pump on the c/h flow.
you generally wouldn't need a zone valve for c/h as the pump act's as the control for the heating.
the boiler would fire immediately for h/w when you turn on the timer as that's the only control you have over the water, when c/h was turned on the boiler and pump should fire.

Hope this helps.

Ian
September 2009