Warm water, no HW pilot, but CH works?

[fingres]

Hi,

I turned off the timers for a weekend whilst away, now the hot water is warm but wont get hot, and I think it's only warm because of the CH.

I have a Potterton Netaheat 10-16, and the pilot light doesn't come on when only HW is turned on. The thermostat on the boiler is set to max. The thermostat on HW tank is at 65 degrees. No settings have changed.

I live in a flat, so I think it's an unvented indirect non-gravity fed system (I'm a novice and been reading Collin's DIY so I could be wrong on the terminology). HW tank is sealed in insulated box and not easy to get to the top.

Any suggestions greatly appreciated!

 

[fingres]

Further to this, I have tried setting both valves near the pump to Manual, but the pilot light still fails to ignite. Both levers on the valves moved smoothly with no real effort, and both 'wound' back to the automatic position when not locked into manual.

Does this rule out a faulty valve? What's the next thing I should check?

Thanks in advance.

(PS - Thought I should also emphasize that the pilot ignites for CH, just not HW)

 

[gas4you]

Open the HW valve manually, then turn the CH on. Does the HW get hot?

If so it is the HW valve head microswitch that has gone. New valve head needed.