H/W passing to C/H

[bewsh]

Alright guys? My mates dad has a y-plan system, and as the title says, his heating comes on with the hot water. Mid-position valve has been replaced by someone 2 weeks ago. Which has helped, they only get warm instead of boiling now. Any ideas what could be causing it? Blockage on the hot water circuit causing the pump to force the valve open slightly?

 

[kris]

Possibly , do u know what brand of valve they installed ? Is the voltage going to the MV correct? Is there a bypass on the system ?
Has he measured the temperature on the coil side of the 3 porter to see if it's that ,

 

[wattsie1987]

Has it ever worked ok? Was the whole 3 port changed body aswell? Could be wrongly coupled returns back feeding if it's always been an issue.

 

[arran197]

Could be a piping issue. When the system is cold, turn the DHW on and does the ch flow get hot by the valve? Need to make sure there's no voltage going to the ch demand on the valve opening it slightly.

 

[bewsh]

Cheers for the advise guys!

They said it used to work fine, but then every customer always says that!!

I'll be checking it out on the weekend, so will check voltages, etc...

 

[gassafe]

Probably only changed the head or there is a pipework issue also!

 

[kris]

That's the thing, it's a lot easier changing a head not having to drain the whole system but how many times is it the paddle inside, too much grimme lol,, I'd bet like said below , they only changed the head lol

 

[cdodds2004]

if its easy to check in the AC check the hw return is the last tee. I fitted a boiler many moons ago and they swore it worked ok before I fitted new boiler. lots of messing about and time wasted found it was piped up wrong and cant of ever worked ok!

just double check if possible were the last tee is. you can also check this by putting just hw on and seeing if the ch flow gets warm. if it doesn't but the rads start to warm up its the last tee in the wrong place!