Hot water only running cool, when Hw only rads come on.

[Yorkie13]

About 2 weeks ago my sister's hot water started running cold, well about room temp.

When she turns on hot water at control, radiators come on??

She has a vented indirect system.

I called round last night sure it would be the 3 way mid position valve or motor. (siemens MA-V322C)

I pulled the metal arm to hot water, waited a while but still only room temp, at best.

I started to think it may not be valve firstly as 3 pipes connected where hot, secondly if valve locked on heating then surely no water would be able to reach hot taps.


Checked pump - ok

As anyone any ideas??

 

[ChrisR]

I pulled the metal arm to hot water

You can't - sort of. The valve spring-returns to HW unless it's stuck, but you couldn't pull it back with the arm.
Take the head off to see if things move.
Also check for air in the pipe going to the HW cyloinder from the boiler. Thre's usually an air vent point.

 

[Yorkie13]

Cheers Chris, I'll give it a try when I go round tonight, I'll let you know.

 

[weareleeds]

Another thing to try Turn off mains supply @ fused spur as it may be electrically powered permanently to htg position (faulty valve head)

 

[Yorkie13]

Found problem. The valve was sticking when turning to hot water.

 

[monkeyboy67]

Yorkie... you have the same mid position valve as I do. Mine is installed in the most awkward place imaginable... trouble I have is the small board inside the valve has come loose so the microswitches aren't working properly... I can't see the valve without the use of a mirror and a torch but even then I cant see how the board attaches to the valve or why it has come loose - did you happen (or anyone) notice?

 

[Yorkie13]

Sorry, I can't remember.
Mine too was in a very tight space. Why do people fit them there?
I'd check for you but it's actually my sister's and she lives 50 miles away.
Sorry mate.