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ShaunCorbs

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What’s your thoughts on this I’m thinking it’s going to gravity circ maybe

down blue arrow upstairs rads return
Up blue arrow cylinder return
Tee below up blue arrow left heating return right cylinder return

even if I install another tee to the right just for the boiler return so that the cylinder is the last I think it’s going to be very close and could gravity anyway but open to your thoughts
 

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I'm struggling to get my head round your beautifully precise schematic 😄. You worried about cylinder return backfeeding through upstairs rads?
If so don't think it will gravity circ through cylinder coil because of Coil orientation.
If it does are anti gravity valves still a thing?
 
I'm struggling to get my head round your beautifully precise schematic 😄. You worried about cylinder return backfeeding through upstairs rads?
If so don't think it will gravity circ through cylinder coil because of Coil orientation.
If it does are anti gravity valves still a thing?

close the blue line is the boiler return back to the boiler so from the cylinder it has to rise then goes into the boiler so I think there s a chance of it going into the upstairs rads
 
If the return from cylinder is lower than flow then I'd think you'll be ok, if they're level then I'd want either a long horizontal run from cylinder or a little anti gravity loop
 
What’s your thoughts on this I’m thinking it’s going to gravity circ maybe
Unless I've missed something, I think you must mean 'reverse circulation' rather than 'gravity circulation'?

If so, I assume you are worried that a proportion of return flow from the cylinder is going to reverse-flow back up the ground-floor-radiators return then mix with the flow to the upper floor radiators and then back to the boiler via the upper floor radiator return?

So, if I've understood what you're saying correctly, I think you're right, there's a potential issue. If the upper and lower rads each have their own zone valve I can't see that your going to get reverse circulation in the 'Why are my radiators hot in the middle of summer?' sense but there'll be some starvation of heat to the radiators when the DHW is heating and both rad zones are supposed to be on.

Following the 3-tee rule would prevent reverse circulation if a single zone valve controlled both GF and UF radiators, which doesn't look like it's the case here. It won't do much to mitigate this 'starvation', which is present any system that doesn't have an independent pump on each zone. Even non-return valves don't fix it because it's a reduction in flow not reversal. It's just what happens when you put heating loops in parallel.

On the one hand people accept that 'when the cylinder starts heating the radiators get cooler'. On the other hand if you don't follow the 3-tee rule, the next guy who looks at the system will point out the fact to the owner and allege, rightly or wrongly, that the system is below par as a result.

Or I may have misunderstood what you were saying. :)
 
did a drawing with a picture @Knappers @Chuck and your correct there is a possibility of the upstairs rads warming when the cylinder is only on via reverse circulation as the cylinder tee isnt the last tee technically the upstairs rads are

yes the ground and upstairs rads are one zone

horizontal pipes from top to bottom

rad flow up and down
ufh flow
rad return
hot 3.5 bar
cold balanced 3.5 bar
cold main 8 bar

would option 2 eg the separate pipe be better as the tees are close i cant see much benefit as there close
 

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Yea 2nd is better but putting 150mm gap between tees would be best, can you kick out to right at bottom?
 
Yea 2nd is better but putting 150mm gap between tees would be best, can you kick out to right at bottom?

not really would have to see how much I could squeeze as the boiler is left hand return
 
Personally, from experience I'd of said you've got more chance of the down Rads heating up than the upstairs.

Tee the Cylinder return up at the bottom (To the right of your current T), and bring the upstairs Rads straight down without a tee out. Hope that makes sense?
 
Actually will be fine, if you get any heat in pipe then it still won't induce a flow
 
@EvilDrPorkChop Down stairs rads won’t heat due to them pipes to the left going around 20m before a tee off / rad
 
Might try it worse case add a scv to the return up as I’ve got to flush the system etc
 
A loop on bottom of upstairs return would do too but looks like you've made that already
 
A loop on bottom of upstairs return would do too but looks like you've made that already

that’s with the sep boiler return as the existing combined it wouldn’t do anything
 
This is what it actually looks like upto date
 

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Tbh I haven’t decided yet I’m going to get the boiler in there tomorrow and depending on space if it’s less than 4” I’m risking well having an experiment if I can get 6-8” I will change it
 
If I've understood what you're saying correctly, I think you're right, there's a potential issue. If the upper and lower rads each have their own zone valve I can't see that your going to get reverse circulation in the 'Why are my radiators hot in the middle of summer?' sense but there'll be some starvation of heat to the radiators when the DHW is heating and both rad zones are supposed to be on.
I don't follow you. You suggest elsewhere that the cylinder return could run back along the rad return. If the rad circuits are on, then how can the return from the cylinder possibly flow back against the current? Pumped water flow cannot in run two directions through the same pipe simultaneously, can it?

Obviously I get that having multiple circuits in use at the same time may reduce head and thus flow.
 
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I don't follow you. You suggest elsewhere that the cylinder return could run back along the rad return. If the rad circuits are on, then how can the return from the cylinder possibly flow back against the current? Pumped water flow cannot in run two directions through the same pipe simultaneously, can it?

Obviously I get that having multiple circuits in use at the same time may reduce head and thus flow.
At the time I wrote my answer, I was assuming that the upper floor and ground floor radiators had their own separate zone valves (there were several shown in the picture) but @ShaunCorbs said in later that they were on a singe zone.

In the actual system, I think that literal 'reverse circulation' can occur when the (single) zone valve to the radiators is closed and the DHW is heating. When the radiator-zone valve is open the 'reverse circulation' will be superimposed on, and hence reduce, the forward flow in part of the radiator circuit and might impair performance to a greater or lesser extent.

Take a minute to sketch a diagram of the pipework it'll make my thinking much easier to understand.
 
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They are 3 zones total ufh, rads, cylinder
 
At the time I wrote my answer, I was assuming that the upper floor and ground floor radiators had their own separate zone valves (there were several shown in the picture) but @ShaunCorbs said in later that they were on a singe zone.

In the actual system, I think that literal 'reverse circulation' can occur when the (single) zone valve to the radiators is closed and the DHW is heating. When the radiator-zone valve is open the 'reverse circulation' will be superimposed on, and hence reduce, the forward flow in part of the radiator circuit and might impair performance to a greater or lesser extent.

Take a minute to sketch a diagram of the pipework it'll make my thinking much easier to understand.
Okay, kind of got you now. Ta.
 
Up the upstairs return and back via downstairs return via splitting tee on flow, induced by convection like on 1pipe system with cylinder return acting as a header.
Is the issue as I see it?...

@ShaunCorbs how did it go?
 
Haven’t filled up but the distance between was less than 5” so opted for a nrv
 
Nrv
 

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110dc temp rated and 11 bar
 

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