S- plan with one valve on the flow & the other on the return...what's going on?

[Savva]

I have a customer with an open vent s-plan system. One of the 2 port valves is on the flow and the other on the return!!! whats that about? Never seen this before, both Heating & HW seem to be working. The boiler needs replacing & I really want to understand how the system works before doing any work. Can anyone shed any light on this? Thanks.

 

[Chuck]

I have a customer with an open vent s-plan system. One of the 2 port valves is on the flow and the other on the return!!! whats that about? Never seen this before, both Heating & HW seem to be working. The boiler needs replacing & I really want to understand how the system works before doing any work. Can anyone shed any light on this? Thanks.

Are you saying one zone valve is on the flow of the HW and the other is return of the radiators zone?

Does the system obey the '3-Tees' rule? If not, the zone valve may be in an unconventional position to stop reverse circulation when the HW is on but the radiators aren't.

A bit more detail about the arrangement would be useful here.

 

[Savva]

Are you saying one zone valve is on the flow of the HW and the other is return of the radiators zone?

Does the system obey the '3-Tees' rule? If not, the zone valve may be in an unconventional position to stop reverse circulation when the HW is on but the radiators aren't.

A bit more detail about the arrangement would be useful here.

Hi Chuck, thanks for the response. Have a look at the pics it's a conventional boiler & I'm saying the one valve is on the primary flow & the other the primary return...both valves are right next to the boiler. One of the valves is after the pump.... I've taken the valve actuators off...they need replacing

 

[Chuck]

Hi Chuck, thanks for the response. Have a look at the pics it's a conventional boiler & I'm saying the one valve is on the primary flow & the other the primary return...both valves are right next to the boiler. One of the valves is after the pump.. I've taken the valve actuators off...they need replacing
View attachment 30238 View attachment 30239

So, is the left-hand valve the HW flow and the right-hand valve the CH return?

 

[Savva]

The valve on the left does the hw & the other does the ch. if you follow the valves up to the next picture you'll see the pump on the left which goes straight back to the boiler on the flow side and the ch valve /22mm also goes directly back to the boiler on the return side! I don't understand it

 

[Gasmk1]

probably because the original didnt have enough room to fit both valves and a bypas on the flow

 

[Chuck]

The valve on the left does the hw & the other does the ch. if you follow the valves up to the next picture you'll see the pump on the left which goes straight back to the boiler on the flow side and the ch valve /22mm also goes directly back to the boiler on the return side! I don't understand it

My guess is that the original system was not S-plan and was then converted to the current arrangement with a couple of corners cut. For example, I think most people would install with the HW return as the last Tee before the boiler. If what we're looking is not just a couple of minor mistakes that someone got away with, I suspect that the explanation will be that there is a bypass hidden away in a location that is awkward to move.

 

[ShaunCorbs]

I would re pipe it correctly

 

[Savva]

Cheers guys much appreciated. I hope they opt for a combi!!! Still niggles me as to how it still works with the ch 2port on the primary return.

 

[ShaunCorbs]

Cheers guys much appreciated. I hope they opt for a combi!!! Still niggles me as to how it still works with the ch 2port on the primary return.

Just the return mate

Primary return is the return to the boiler after any t's (e.g. Main flow and return are know as primary flow and return)

And sometimes commercially pump on flow 2 port on return to stop reverse circulation

 

[deg]

You are a bit like me mate, In this case i think you are over thinking things.
Just a valve to stop the circulation.

 

[Starky]

To me it looks like there are two returns In the picture with the pump, the two port is there to stop any heat going back down to the heating.