UFH - bunching flow and returns?

[Bramco]

Hi, We're about to get the slab laid and have the UFH layout from the timber frame contractor.

 

As you can see the plant room is to one edge of the layout and therefore almost all the UFH loops have to go through the hall and the doorway into the living space (off to the right of the diagram below). The proposed layout has the flow and returns for about 7 or 8 loops all bundled together as you can see from the diagram.

 

I'm concerned that this will cause that area to warm up very quickly and therefore warm the returns before the slab at the ends of the loops are actually up to temperature. So measurements of the flow and return temperatures wouldn't give a true indication of the temperature of the slab.

 

Would it be better to have the flow and returns more evenly spread across the hall area. They would of course heat this area as they are heating the rest of the zones.

 

Edited August 7, 2021 by Bramco

[joe90]

I didn’t like the idea of multiple pipes through doorways so (with the consensus on here) ran some pipes under walls (with a pipe sleeve of overflow pipe). This reduced pipe bunching and also reduced loop length a little.

[Russell griffiths]

I had a design like yours so I spaced flow and return at 150 like the rest of the house so if you shorten the pink purple loop and space them evenly across that area. 

Lose all runs in hall and just cover with flow return. 

[Bramco]

Thanks for the good ideas.

 

I'm still wondering though whether I'm worried about nothing.   Would be interesting to hear from anyone that followed a plan like the one we have as to whether it was OK or whether it caused problems.

 

Simon

[Bramco]

@joe90 and @Russell griffiths

 

 

Just been looking at this again and wonder actually whether it wouldn't be better to have 2 manifolds, one in the utility to feed that area and the living space a total of 6 loops which could actually be reduced maybe to 5 as the long runs would be a lot shorter.

 

That would leave a manifold in the plant room itself to handle the remaining 7 loops.  

 

Would require a feed and return from the buffer tank across to the utility which could run through the ceiling.   And 2 separate pumps the living space would be one zone, so that would be good - I think...

 

Simon

[joe90]

  On 07/08/2021 at 15:20, Bramco said:

as the long runs would be a lot shorter.

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If I remember correctly the loops should not be too short as they will be too short to loose their heat to surrounding flooring. I think optimum length is 100m (please correct me if I am wrong!.

[Bramco]

  On 07/08/2021 at 16:02, joe90 said:

If I remember correctly the loops should not be too short as they will be too short to loose their heat to surrounding flooring. I think optimum length is 100m (please correct me if I am wrong!.

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Sorry if I didn't write that well. I meant that I could do fewer loops but keep them about 100m or a bit less. So 6 loops of 80 to 100m could become 5 loops of around 100m.  We'd be losing the runs from the living space through to the plant room - so 6x2x say 6m  is about 70 odd metres less.

 

Hope I've explained that better this time.

 

Simon

[Nickfromwales]

  On 07/08/2021 at 16:22, Bramco said:

 

Sorry if I didn't write that well. I meant that I could do fewer loops but keep them about 100m or a bit less. So 6 loops of 80 to 100m could become 5 loops of around 100m.  We'd be losing the runs from the living space through to the plant room - so 6x2x say 6m  is about 70 odd metres less.

 

Hope I've explained that better this time.

 

Simon

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Is this in screed or a passive raft / slab?

[Bramco]

@Nickfromwales

 

 

passive raft/slab

 

Simon

[Bramco]

  On 07/08/2021 at 15:20, Bramco said:

Just been looking at this again and wonder actually whether it wouldn't be better to have 2 manifolds, one in the utility to feed that area and the living space

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Talking to myself here but I think it's normal in a 2 storey house to have a manifold for each storey - this may not be true of course...

 

But if it is, then having a 2nd manifold in our utility room for the living space zone would be analogous to what is done for a traditional 2 storey house.

 

Simon

[andy]

  On 08/08/2021 at 14:00, Bramco said:

@Nickfromwales

 

 

passive raft/slab

 

Simon

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Hi  Simon

 

I had a similar desgin, I sleeved the majority of the pipes (and all flows) where they bunched to minimise heat transfer in areas I didn't want to overheat.  I used this suff (red for flow, blue for return):

https://pswtradesuppliers.co.uk/ufh-foil-pipe-edge-insulation/136-16-18mm6mm-pipe-insulation-lagging-blue.html

 

This has worked fine with no excess heat in areas I didn't want it.

 

And I have a split floor on my slab with a manifold on each floor.

 

Hope that helps!

[Bramco]

  On 09/08/2021 at 09:19, andy said:

Hi  Simon

 

I had a similar desgin, I sleeved the majority of the pipes (and all flows) where they bunched to minimise heat transfer in areas I didn't want to overheat.  I used this suff (red for flow, blue for return):

https://pswtradesuppliers.co.uk/ufh-foil-pipe-edge-insulation/136-16-18mm6mm-pipe-insulation-lagging-blue.html

 

This has worked fine with no excess heat in areas I didn't want it.

 

And I have a split floor on my slab with a manifold on each floor.

 

Hope that helps!

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Great help - thanks

 

Simon

[Nickfromwales]

  On 08/08/2021 at 14:00, Bramco said:

@Nickfromwales

 

 

passive raft/slab

 

Simon

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Hi.

With such low flow temps ( as associated with these types of emitter ) I really doubt that you’ll get any issues whatsoever. I would run the pipes under the stairs though, instead of dog-legging through the plant corridor. Come up into the manifold from behind, or even relocate the manifold under the stairs to free up some more space there if there’s nothing else under the stairs.

  On 09/08/2021 at 09:19, andy said:

I used this suff (red for flow, blue for return):

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That would be better than nothing, but again I think probably unnecessary with such very low flow temps.  

[Bramco]

@Nickfromwales

 

Thanks Nick.

 

One last question, should we get them to lay the pipes in a snail shape or as them have them, serpentine?    (If those are the correct terms of course)

 

Simon

[Nickfromwales]

I’ve never laid serpentine in any of my installations. Reverse / inverted is the best layout afaic and allows for much better heat dispersion and almost zero 180o ‘U’-turns, which are not great for enhancing flow rates.

Also, if installing on anything less than 200mm centres, inverted is the only layout that allows for tightly packing in the pipes. 
On my current project, an MBC TF passive raft, the pipes are going in at 100mm centres to maximise water volume in the system ( to aid the operation of the ASHP + cooling ) and that can only go in via inverted at that distance apart.

If going DIY then serpentine may look simpler, but inverted really is a doddle to lay, me imho easier than serpentine as you’ve not got to perform so many ‘U’-turns ( which are difficult / easier to kink the pipe with when performing scores of them with each loop ? ). 

[Nick Laslett]

This might be useful to some people, the “Reverse / inverted” pattern is also know as “counterflow” serpentine in software like LoopCad. 

[Bramco]

  On 09/08/2021 at 18:31, Nickfromwales said:

On my current project, an MBC TF passive raft, the pipes are going in at 100mm centres to maximise water volume in the system ( to aid the operation of the ASHP + cooling ) and that can only go in via inverted at that distance apart.

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Interesting - ours is MBC and they're coming to put in the slab from the middle of next week.

Not sure I understand about maximising the water volume - won't this also increase the number of loops?

 

Simon

[Nickfromwales]

  On 10/08/2021 at 11:52, Bramco said:

Interesting - ours is MBC and they're coming to put in the slab from the middle of next week.

Not sure I understand about maximising the water volume - won't this also increase the number of loops?

 

Simon

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Yes, exactly why I’m doing it !!

[Nickfromwales]

  On 10/08/2021 at 11:52, Bramco said:

Not sure I understand about maximising the water volume - won't this also increase the number of loops?

 

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How are you heating yours? ASHP?

[Bramco]

  On 10/08/2021 at 13:06, Nickfromwales said:

How are you heating yours? ASHP?

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ASHP - the heat loss analysis indicates we'll only need a small one of course.  Did you simply tell the timber frame folks to do the loops the way you wanted them?

 

Simon

[Nickfromwales]

  On 10/08/2021 at 13:16, Bramco said:

 

ASHP - the heat loss analysis indicates we'll only need a small one of course.  Did you simply tell the timber frame folks to do the loops the way you wanted them?

 

Simon

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I am the principal M&E coordinator on that project, so the system is being installed to my spec / guidance. 
MBC have many of these under their belts, and they work fine for heating / cooling etc ‘out of the box’, and typically go in at 200mm centres in a serpentine layout unless someone specified differently ( for a reason ). Deviation of course causes uplift in prices  
For this project I am using very particular equipment, and also integrating cooling via slab + MVHR, so have done calcs which are unique to this sizeable ( 400m2 ) dwelling. 
One size does not fit all, so please do not focus too much on this detail for your build as it may not be relevant.

[Bramco]

  On 10/08/2021 at 13:35, Nickfromwales said:

Deviation of course causes uplift in prices  

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You can say that again !!!

 

But more on topic, what you are saying is that serpentine is fine with their slabs..   so 'Don't panic!'  as the famous H2G2 quote has it.

 

Simon

 

Simon

[Nickfromwales]

  On 10/08/2021 at 13:49, Bramco said:

 

You can say that again !!!

 

But more on topic, what you are saying is that serpentine is fine with their slabs..   so 'Don't panic!'  as the famous H2G2 quote has it.

 

Simon

 

Simon

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Yup. They’ve done more like that than I’ve had ‘lamb dinners’   

[Bramco]

Thx.

 

Simon

[RHayes]

  On 07/08/2021 at 15:20, Bramco said:

@joe90 and @Russell griffiths

 

 

Just been looking at this again and wonder actually whether it wouldn't be better to have 2 manifolds, one in the utility ...

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Agree with Simon, when designing our systems we always seek to put the manifold in a central location for that reason.  If its not too late and if supply pipework runs supported it I'd recomend putting the manifold in the utility and send some pipes under walls, that way you minimise any pipie bunching and reduce transit pipework lengths.  However coming back to the design, we have done many like that over our 18 years and don't typically have a problem.  Insulating the flow pipework is a good idea where they are going through a narrow hallway as you have here.