Hot Water too hot

[sotal]

I've got a Y plan central heating system.

Something seems to have gone wrong and the hot water is always hot.

The system has an electronic timer with seperate functions for HW and CH, but even with the HW switched off the HW is heating to approx 80 degrees C (according to where the cylinder stat clicks).

I'm suspecting something has gone wrong with the Y Valve - there is a lever on the side but I can't remember what it does now. Is there anything I can do with that?


It's a conventional boiler system with an electronic timer unit for HW and CH but the CH stays on 24/7 on that because we have a remote programmable room stat which then switches it to various temperatures at different times of the day. Other than that it has a pipe stat to overrun the pump.

 

[twgas]

I would suspect the 3port valve is not shutting the hot water port when the heating is on.
why do you need a pump overrun pipe stat?

 

[sotal]

I added the pipe stat a year or so ago after advice on here, when the heating system stopped, the pump stopped instantly this caused hot water to rise up the vent pipe and into the tank in the loft which then overflowed and out out the overflow pipe.

Adding the pipe stat keeps the pump running for about 10 mins after and seems to have perfectly cured it.

The whole system has been working properly until a few days ago. I've now switched off the HW about a day ago but it's still getting up to 80 during the day when the heating is on.

It sounds like your thinking the same with the 3 port valve - is there anything that can be done or is it a replacement that's needed?