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eddiebrown424

Hi

Installing a new central heating system in a three storey house. I am going to zone the 2 upstairs floors from the ground floor. Question is do i have a common return or do I have to have two seperate systems per se.

thanks

Eddie
 
Hi Eddie, the return is the same as if it was just one system. Three separate flows from your zone valves to each floor.
 
Non return valves will solve the reverse circulation, however I would run independant returns from each zoned system back to the boiler and tee in just before boiler.
 
Hi All thanks for the debate.....

I was wondering if I keep all my flows and TRVs on the left how reverse flow would occur.....

Excuse my niavety..

its a pressurised cylinder could I not connect the returns here as it would save a lot of pipework.

thanks:smiley2:
 
Hi All thanks for the debate.....

I was wondering if I keep all my flows and TRVs on the left how reverse flow would occur.....

Excuse my niavety..

its a pressurised cylinder could I not connect the returns here as it would save a lot of pipework.

thanks:smiley2:
left of what ?
 
Hi Dancinplumber

Left of what ???? sorry I dont understand.

also is there a difference Teeing the seperate returns in close to the boiler as oppossed to near the cylinder is it just a temperature thing?

Thanks

Eddie
 
sorry I forgot would the returns T-into the primary pipe just once or would it have to be three T's. also could I T-in the top floor return close to the boiler (its in the loft) and the lower and middle floor into the primary at the cylinder?

Cheers:dizzy2:
 
Hi All thanks for the debate.....

I was wondering if I keep all my flows and TRVs on the left how reverse flow would occur.....

Excuse my niavety..

its a pressurised cylinder could I not connect the returns here as it would save a lot of pipework.

thanks:smiley2:
???? left of what ? :)
 
Hi Dancinplumber

Left of what ???? sorry I dont understand.

also is there a difference Teeing the seperate returns in close to the boiler as oppossed to near the cylinder is it just a temperature thing?

Thanks

Eddie
last tee always cylinder :)
 
ahh I get it now...." Left of what"... I meant on the left of the rad so water would only travel one way (i thought??).

With regards to the cylinder can the return not connect before the two port valve and form part of the by-pass?

Appreciate your advice

Eddie
 
I always take my zone returns back to the boiler, flow and trv on right hand side of radiator.
 
thanks Simon. As three connections or can I couple them close to the boiler or would this make it a common return?
 
i would run them to the position your zone valves are fitted, either the boiler or Air cub. if the a/c then run your 28/35mm primarys to there and common in correctly under floor or inside the cub.

dont fit non returns, especially under a floor.
 
Running independant return from each zone does mean more pipework yes.
When you say TRV's to the left that makes no sense, TRV's should be positioned accordingly to the flow of air in the room, for example a TRV on the left of a rad and a window on the right of the rad means the section of room with the TRV could be slightly hotter due to drafts from window, putting a TRV on the right in this case should mean equal teperatures.
Reverse circulation will occur when water is pumped through the coil of the cylinder, the water still carries enough charge from the pump and works it way though the returns of the heating circuit/circuits. If you were to tee the returns in in the cylinder cupboard and use non return valves it would stop reverse circulation, however should one of those non eturn valves ever fail then you would get reverse ciculation, this will cause boiler inefficiency (how much depends on the system/systems) and you probably wont know until your next fuel bill. If you run independant returns you should never get reverse circulation and in turn boiler inefficiency, even if the water returning still carried some pump charge the pump will then be sucking that water through the boiler and pumping back round the circuit/circuits.

P.S unvented hot water cylinders makes no difference to potential reverse circulation.
 
thanks sjb6..... Was someone winding me up many years ago when i was told rads go under the windows, has it changed coz I always put them there. The plumber I worked with always put the flow on the left and at the top to prevent crossovers i guess is it the right now and is there a reason?
 
No he's not winding you up, the common place for rads is under the window but heat loss has to be considered ie. non double or tripple glazed windows, heat running up behind curtains etc, ultimately they can go were ever the person or customer wants.
Rads often have flow left top and return right bottom.
And when you say cross overs i take it you mean flows and returns running to rad, in which case bare in mind most TRV's these days are reversable, meaning they can be fitted either end of the rad.
 
so finally the best way would be to bring three returns back close to the boiler and join them independently i.e three t's.

And thnks all again for the advise:shades_smile:
 
I agree, with this configuration no gain in joining returns.
If the boiler and cylinder were together on the same level (top or ground floor) would it hurt to join the returns for the two furthest heating zones?
The floor the cylinder is on wouldn't matter as it would be separate any way.
I have always done it like this with no problems but don't want any in the future.
 
so finally the best way would be to bring three returns back close to the boiler and join them independently i.e three t's.

And thnks all again for the advise:shades_smile:
Hot water return should be the last on the system.
i would only have one return,
 
I normally have the flow on the left of the rad and the return on the right but I don't think it makes any difference.
 
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