S plan return back feed??Hi

[Lidds82]

Hello everyone my first post so here go's.
I have a combi boiler heating system which is zoned for upstairs and downstairs rads.
I have noticed that when only one of the zones is calling for heat and the other one is not, the rad circuit that is off is getting luke warm. It seems that the return pipes of the rads that are supposed to be off is getting warm and heating the rads. Is it possible for the boiler to force the return flow back ip into the rads on the off circuit? Is this a balancing problem or something else? Any advice appreciated.

 

[Deleted member 120897]

It’s probably more likely let by of the zone valve that’s off, so in effect the paddle isn’t seating correctly.

 

[ShaunCorbs]

Or the motor is kinda stuck open a smidge

 

[Lidds82]

I did wonder that , but would that not make the flow side of the rads warm and not just the return?

 

[ShaunCorbs]

Has it always done this ?

 

[Lidds82]

This system split zone part of the heating system has not been in action for very long and also the heating has been off because it was still quite warm. I've only just noticed it now we have turned the the heating on due to it being colder .

 

[Ric2013]

I'm told this can happen. I've been promised an explanatory diagram even. But yet to understand why!

 

[Deleted member 120897]

I did wonder that , but would that not make the flow side of the rads warm and not just the return?

Depends on how it’s setup and what you’re classing as flow and return.

 

[Lidds82]

The side that gets warm on the rads is the locksheild valve side. Not the TRV side. I'm just presuming that the rads are plumbed the correct way round. If I fire the heating up from cold and have a quick walk round the radiators ,the TRV side is the pipe that gets warm first.