Faulty 3-way valve?

[mutley123]

Hi Guys

Had the three-way valve on our heating system changed last year as the heating came on when just hot water was selected.

We are now back in the "hot water only" season and the same thing is happening again.

Have checked the valve and the selector is moving correctly when I change from "heating only" to "heating and hot water" to "hot water only", but the heating is still coming on.

I'm guessing that it's a dodgy valve body - anyone got any other ideas before I get the plumber back in?

Thanks

 

[misterdubya]

Reverse Circulation?

Mr. W.

 

[45yearsagasman]

I would not suspect reverse circulation unless there have been some system pipework alterations recently.If there have then it could well be the case but more likely system debris has caused the valve to not seat correctly and is passing to heating.Was the complete valve replaced or just the powerhead?
Did the system ever work correctly?

 

[mutley123]

Thanks for the replies guys.

Can't say whether it ever worked correctly - we bought the house last year and noticed a problem with the rads coming on when the hot water was on. Had the 3-way valve replaced (the whole thing) in October and of course the heating has been on ever since .....

The previous owners weren't very big on maintenance and its hard to imagine that they would have noticed / cared.

There was a downstairs extension built about 5 years ago and it does seem that maybe its the rads in there which are warming up first, which possibly points to reverse circulation (which I had never heard of before but I have now got the concept thanks to google). I will do some investigation to try and narrow down the cause.

 

[simond]

It'll be reverse circulation, everything you have said points to that.

Start rolling the carpets up!

 

[45yearsagasman]

If it is reverse circ then you will be looking for a rad return connected to the main return after the cylinder return tee.
There is a simple test to confirm RC
Turn both heat and hot water on and check the flow direction through suspect rads.
Get system luke warm and then turn off the heating at the timer and quickly feel the rad flow and return.If there is RC then the flow direction will reverse and continue to heat the rad.
If it still heats with the flow still the same then its the valve.

 

[misterdubya]

It'll be reverse circulation, everything you have said points to that.

Start rolling the carpets up!

The handymen would be shoving TRV's on.

OP, it may need a bit of replumbing, or put in 2 zone valves. (oh, more re-plumbing). Personally, find the CH return, and if it is after the HW return you would be best to re-pipe (3 Tee rule). Us plumbers aint stoopid.

Mr. W.