Heating Contentiously On With Hot Water

[Harris]

I hope some one help me. Facing problem with my central Heating. I called the gas safety approved plumber to change the valve and I am afraid its not working properly since.
Hot Water working fine, if its on on its own.
Heating working fine as well, when turn on on its own. Only heating without hot water.
But when I turn both on continuous same time. Heating by pass thermostat and contentiously on with boiling radiators. When I turn hot water off its back to normal and can control with Thermostat
Any one can tell me what is the issue. We change programmer as well but same issue.
I will appreciate your reply.
Many thanks

 

[Dotty]

Get him back out, he's wired it up wrong.

 

[LaMont5way]

So the heating circuit is only controllable by the room thermostat whilst there is a demand for hot water from the programmer?

 

[Harris]

Hot water works fine but When I turn on heating and hot water together. no control for heating by thermostat. Hot water works fine with or without heating.
If I turn off hot water heating works fine and can control by Thermostat. I hope it make sense.
Plumber changed the 3 way valve and the problem appeared then he said its timer issue . Now Changed the timer but same issue.

 

[Rckape]

Like Croppie said, get your plumber back. He's connected the valve up wrong.

 

[Harris]

Thanks for all your help. I thought this is the case but he insist that wiring is right. I have called him to come back. Lets see what he says on Friday. Will let you know.
Many thanks