DHW Secondary return configuration.

[Jonnyjambo]

Hi

Anyone help and advise on the best option for a DHW secondary circulation (SC) layout.

Scenario 1

I need to install SC in a large new build. The unvented cylinder will be in the middle of the house and so I would like to have two SC ‘loops’ i.e. T off the hot from the cylinder and go to each end of the house. Then install 2 return legs and common them before a single pump as it returns into the cylinder. In this approach I anticipate having to add valve to balance each of the loops so the pump is pulling both legs equally and not favouring any particular loop.



Scenario 2

Can I have some outlets off the secondary return loops and some low use hot taps not? So, I would again T off the top of the cylinder and create a SC loop with one of the branches of that T and take the other branch take straight to a HW tap(s) without a return?

If this is possible, would I have to have a one way valve to the none SC leg to prevent the true SC loop pulling on it?



General question.

Is it still best practice to have the SC return leg a pipe size small than the supply leg?

If reducing the return pipe is the correct way, in scenario 1, would I do both returns in size lower or once they are commoned before the pump drop a size. I.e. say the out let pipework from the cylinder is in 22mm from the furthest point back drop to 15mm or stay in 22mm for the return legs and drop to 15 before the pump once commoned

Can spur off the SC loop and then spur off that spur again. I.e. T off the SC loop to feed the shower and the basin with only one pipe.




Many thanks.

 

[Scott_D]

Both could work. Best t keep it simple though.
Are you G3?
It needs to be copper or mlcp, insulated, check valve, bronze or SS pump.

 

[Jonnyjambo]

Thanks Scot_d

Yes I’m G3.

Any thoughts on spurring off a spur from the loop? Personally can’t see any reason why not, the SC is still supply HW close to the draw off points so minimal wastage.


Also thoughts on dropping a size for return leg(s) back to the pump in a size lower e.g from 22 back to 15?

 

[Scott_D]

15 is fine for the return.
Sometimes 10mm is enough, it only needs to circulate.
Spur off a spur would depend on pipe size and demand.