OFCH probs, no hot water

[thewilk]

Our OFCH has been playing up since Christmas. Oil open system, it has 2 zones, upstairs and down, and a seperate circuit for the hot water.

Few months ago it started firing up, even when timed to be off. In the middle of the night the boiler would fire up and the radiators start to heat. We controlled this by simply turning the power to the system off.

Now though, the heating system is working, but we cannot get hot water. I thought maybe the relays had gone in the timer/control switch so I replaced this, but still the boiler will not fire up if only HW is selected.

Even if CH and HW are selected, the rads heat but no water. Now think that the power valve for the water circuit has gone. Is this the likliest cause?

 

[thewilk]

Bit of an update. Took the actuator off the power valve for the HW circuit and manually turned the valve to the open position. Watching the actuator whilst it is due to be in operation, it does seem to be turning OK.

Ran the CH and HW in the on positions for an hour, with the valve manually open as above, still no HW coming through, although there are hot pipes leading to the HW tank. Only things I can think of now are a faulty stat at the HW tank, or a boiler problem. The boiler is a Grant 50/90 euroflame.

Anybody any advice??