One vs two manifolds?

[oranjeboom]

After a number of UFH quotes I have ended up with 2 that I need to choose from for my 150sqm floor area.

 

One provider (Provider “W”)has quoted from 2 manifolds (7 ports) due to the long pipe runs. The other has provided just the one 12 port manifold (Outside bedroom 4) and some of their pipe runs are just over 100m (think the allow for 105m). They have not elaborated on how they achieve this.

 

I have attached a floor plan showing locations of manifolds (“Man 1”, “Man 2” in red ). Green areas are those depicting locations which will be offlimits to UFH (Kitchen units, toilets, built ins etc), and those in red, are further areas that won’t accept pipework (structural additions mostly). Biggest issue is the long pipe runs to sitting room/garden room if I am just using one manifold in location outside bedroom 4. That’s why provider “W” had added another manifold in entrance hallway. The additional manifold means they are  £400 dearer that the other quote. Single manifold means that most of the hallway will just be feeds going off to control the kitchen/garden/sitting/dining rooms, so reducing temps in those areas will ultimately impact temps in the entrance hallway area.

 

I don’t mind paying the additional £400 if it means a more efficient system. However, having 2 manifolds, also means two pumps to power and more parts to go wrong. “W” will have 4 loops in the garden/sitting/dining room. I suspect that the other provider may simply have put in 5 loops to keep the lengths down. “W” has essentially said this is the best they can do.

 

I have had a play with loopcad but that’s not really helped me with any decision making. So seeing whether the experts have any real life experience here / opinions that may sway me to go for 1 vs 2 manifolds. Efficiency is what I am after, but I also don’t want to be shelling out for a new pump every few years if it’s being overworked.

 

FYI:

·         150mm pipe spacing

·         Pipework tied to mesh in concrete (no screed)

·         Boiler location in loft above dining room on rightermost wall

·         EWI, 3G glazing, 300mmEPS (or PIR equivalent) in most floors

[ragg987]

I can offer my experience - we have 1 pump driving 160m2 worth of UFH at 150mm centres, though in our case this is aplit across 2 manifolds in basement and ground floor. This still reprsent over 1,000m of UFH pipe.

 

That single pump is running at lowest speed setting, the manifolds are essentially wide open (bit of throttling to prevent overheating in basement). There is no issue distributing the heat with this arrangement. I do not need the pump to be running any harder as the capacity of our ASHP is only 7kW though in most cases they are probably carrying 2 to 3 kW.

 

It seems a single manifold shoule be fine.

 

Our UFH design assumed that a much higher flow of heat would be required in the UFH as they base it on regs rather than passiv levels. In that case speed and hence pressure would increase, so a 2-manifold scenario could come into play.

[ProDave]

MAN1 looks pretty central. 12 zones seems a lot? 1 per bedroom, one for bathroom and wc, one for kitchen and 3 for living sopace would probably be plenty.Even saying 2 for kitchen and 3 for living space, that's only 10 zones.

 

I would not have a zone for the hall. We have and it never comes on. There's so little outside wall to loose heat and so much internal wall to gain heat, plus you will have incidental heat from pipes running under it.

 

If you can find a way to route pipes under the wall from the study to the lounge it would make pipe runs easier.

 

200mm pipe spacing works well for us on a house with ordinary levels of insulation so I would say 150mm is too close.

[oranjeboom]

56 minutes ago, ragg987 said:

I can offer my experience - we have 1 pump driving 160m2 worth of UFH at 150mm centres, though in our case this is aplit across 2 manifolds in basement and ground floor. This still reprsent over 1,000m of UFH pipe.

 

Our UFH design assumed that a much higher flow of heat would be required in the UFH as they base it on regs rather than passiv levels. In that case speed and hence pressure would increase, so a 2-manifold scenario could come into play.

1 pump with 2 manifolds? Didn't realise that could work with just 1 pump. Could be an option for me maybe with the pump in loft feedind both the manifolds downstairs.

I have been quoted between 1000-1100m of pipe. 

Not passiv levels here, but should be a lot better than BRs!

 

46 minutes ago, ProDave said:

MAN1 looks pretty central. 12 zones seems a lot? 1 per bedroom, one for bathroom and wc, one for kitchen and 3 for living sopace would probably be plenty.Even saying 2 for kitchen and 3 for living space, that's only 10 zones.

 

I would not have a zone for the hall. We have and it never comes on. There's so little outside wall to loose heat and so much internal wall to gain heat, plus you will have incidental heat from pipes running under it.

 

If you can find a way to route pipes under the wall from the study to the lounge it would make pipe runs easier.

 

200mm pipe spacing works well for us on a house with ordinary levels of insulation so I would say 150mm is too close.

I don't have 12 zones. That 12-port manifold will be feeding multiple loops in a room (like the lounge/garden/dining room) but that will end up being one zone. Looks like I have 8 room stats in both quotes.

 

Want to got for 150mm centres to be 'safe' rather than 200mm. One of them said "why not go for 100mm if it's efficiency you are after...".

 

Can't go through the study wall, but could go through entrance hall/lounge wall to save a few metres.

 

I did wonder whether to have a hall zone or not. The living area is a lot of glazing, so potentially needs less heat being fed there with solar gain. So on some days the hall may still feel cold in comparison to those areas, hence the need for its own zone.

[RandAbuild]

Our GF UFH has just been installed - 6 circuits amounting to about 600m of pipe @ 200mm centres, the longest being 103.4m.

A single manifold should be fine, as long as the manifold is fairly central in the layout

[PeterW]

I've done 400m off one 5 port manifold and the issue you have is that the manufacturers like to quote at low deltaT so they don't get caught out with not enough heat being available. 

 

Persevere with LoopCad and it's excellent - mine were accurate to within 10m overall and I used the Wunda trays. Zip tying to mesh will be pretty easy if you can space to the mesh size. 

 

Is it ASHP or gas boiler ..?

[Nickfromwales]

I bolted two manifolds together ( 7 + 5 ), one pump one TMV / blender set with no issues, in a draughty poorly insulated house with 2.9m ceiling height. Didn't have enough space to put one long manifold in so just joint them with bent irons so the manifold went around the corner of the cupboard under the stairs. ?

At least 5 loops were just short of 100m and one was around 130m. Worked like a dream. 

[ragg987]

In our case the pump and circuit valve are controlled by the ASHP and the manifolds are completely passive and have no blender either. One manifold is in the same room as the ASHP and the other is in the basement with approx 10m of copper pipe between.

 

Water temperature modulation is also controlled by the ASHP, based on set-point, internal and external temperatures.

 

https://www.theunderfloorsuperstore.co.uk/wet-underfloor-heating/manifolds/emmeti-underfloor-heating-manifolds/emmeti-underfloor-heating-manifold

 

 

[ragg987]

On the pipe spacing, it is a balance you need to strike.

 

With 200mm spacing you need the flow to be hotter than with 150mm to emit the same amount of heat. Of course 100mm will allow you to run cooler. With an ASHP, cooler is more efficient.

 

Why not 100mm? A bit like asking why not target U-value of 0.05 instead of 0.1 - diminishing returns at some point. Also, the pipe loop-back with 100mm spacing would bell out, with 150mm spacing it is more comfortable.

[oranjeboom]

On 3/20/2017 at 14:40, PeterW said:

Persevere with LoopCad and it's excellent - mine were accurate to within 10m overall and I used the Wunda trays. Zip tying to mesh will be pretty easy if you can space to the mesh size. 

 

Is it ASHP or gas boiler ..?

Had another attempt last night. Just managed to lose the flamin' background floor plan somehow.....grrrrr! Not pretty, but I can see at least see where the metrage is going. Longest loop appears to be the living room areas as expected, but the dining room circuit could extend into the lounge area. Or potentially add an extra circuit in the lounge/garden room areas.

 

Changed my mind from ASHP to gas boiler. Potentially do that later when the house has convinced me it's good enough for an ASHP!

On 3/20/2017 at 14:54, Nickfromwales said:

I bolted two manifolds together ( 7 + 5 ), one pump one TMV / blender set with no issues, in a draughty poorly insulated house with 2.9m ceiling height. Didn't have enough space to put one long manifold in so just joint them with bent irons so the manifold went around the corner of the cupboard under the stairs. ?

At least 5 loops were just short of 100m and one was around 130m. Worked like a dream. 

130m? That sounds somewhat reassuring then with my longest around 117m, unless I can get Wunda to re-look at their design.

 

On 3/20/2017 at 16:37, ragg987 said:

On the pipe spacing, it is a balance you need to strike.

 

With 200mm spacing you need the flow to be hotter than with 150mm to emit the same amount of heat. Of course 100mm will allow you to run cooler. With an ASHP, cooler is more efficient.

 

Why not 100mm? A bit like asking why not target U-value of 0.05 instead of 0.1 - diminishing returns at some point. Also, the pipe loop-back with 100mm spacing would bell out, with 150mm spacing it is more comfortable.

 

Yeah, hoping 150mm should suffice, especially with a boiler at this stage, maybe an ASHP in future.

[Nickfromwales]

2 hours ago, oranjeboom said:

Changed my mind from ASHP to gas boiler. Potentially do that later when the house has convinced me it's good enough for an ASHP!

Have you included a buffer or TS to compliment the boiler setup? Quite essential if the heat requirement is low as the boiler may never end up condensing ( if feeding th Ufh directly ). 

[ragg987]

If I had mains gas I would have used that and ASHP would not be a consideration. Running costs are pretty similar, but capital costs on gas are much lower.

[oranjeboom]

6 minutes ago, ragg987 said:

If I had mains gas I would have used that and ASHP would not be a consideration. Running costs are pretty similar, but capital costs on gas are much lower.

Yes, to start off with I looked at a GSHP and cried at the cost and relative marginal improvement on an ASHP. Piled foundations then meant I had to rein in my costs so the ASHP had to go too. Wife prefers cooking with gas too. She asked me how she was going to cook with an ASHP.

 

Same applies to my manifold situation now - I see no real benefit in having 2 rather than 1. About £400 extra to have an additional one in another location including all the extras (pump, wiring box, actuators, valves...). With one manifold, there may be more 'usage' in that solitary pump and a bit more metrage in pipework but less capital cost. I may have to replace a single pump sooner rather than having 2 pumps, but that replacement pump isn't going to cost me £400.

[oranjeboom]

On 3/21/2017 at 23:01, Nickfromwales said:

Have you included a buffer or TS to compliment the boiler setup? Quite essential if the heat requirement is low as the boiler may never end up condensing ( if feeding th Ufh directly ). 

HI Nick, 

 

This was going to be my next headache, trying to understand what I would need in terms of a TS. Probably should have that decided really before I go for my final choice of UFH setup, but reckon I can delay my TS choice until later. Will need to have a family meeting to decide how many showers people intend to take when living in 'normal' conditions again to determine heat and water demands. I may come knocking on your door later!

[Nickfromwales]

How many bathrooms / occupants? Could you get away with a hi-flow combi?

[oranjeboom]

On 3/23/2017 at 07:01, Nickfromwales said:

How many bathrooms / occupants? Could you get away with a hi-flow combi?

Hi @Nickfromwales - just seen your question now. 2 bathrooms and 4 human occupants. One's soon to be a teenager so maybe that either counts as 2 humans depending which way they sway on the cleanliness front. Not looked at boiler options for a while and I was going to tackle that once I approach a decent plumber, but would need some ideas before they just fit whatever suits them!

 

I've finally got my manifolds down to one instead of two. But now the flamin' designers have realised that my existing hallway cupboard is not long enough to fit the 12 port manifold (905mm). I'm about 100mm short. It's going to be unsightly to have a cabinet elsewhere in the hallway and my other positions are very limited. Can I rotate the manifold 90 degrees? I have seen one like this, but I'm sure there are reasons not to go down that route! I'll probably end up knocking down a wall in order to extend the cupboard size.

 

[PeterW]

Two manifolds can be joined with a couple of brass elbows. You can go round a corner then ....

[oranjeboom]

Just now, PeterW said:

Two manifolds can be joined with a couple of brass elbows. You can go round a corner then ....

The problem I had was they they were charging approx £350 more for having two manifolds in the first place. But that was for having two of them in different locations in the house (see plan at very top). Cupboard is about 800 x 350 (internal dims) so can't go 'round a corner', but potentially could have one above another. Would that still require 2 pumps, or could I have 1 operating both in this configuration?

[PeterW]

Ask @Nickfromwales as I think he did one like this. Only need one pump. 

[Nickfromwales]

33 minutes ago, oranjeboom said:

But now the flamin' designers have realised that my existing hallway cupboard is not long enough to fit the 12 port manifold (905mm). I'm about 100mm short.

 

Designers, eh? ?

So, can we assume they have already suggested separating the pump and blender from the rails?

 

[oranjeboom]

4 hours ago, Nickfromwales said:

 

Designers, eh? ?

So, can we assume they have already suggested separating the pump and blender from the rails?

 

 

900mm is just for the manifolds I think, and does not even include the pump and blender!! Will confirm that tomorrow though.

[Triassic]

On 23/03/2017 at 07:01, Nickfromwales said:

How many bathrooms / occupants? Could you get away with a hi-flow combi?

Only one bathroom! If the teenager is female you'll never get in to use the shower!

[PeterW]

An 8 port and a 4 port in tandem will fit with elbow on the corner - that shouldn't need much engineering to fit it and will be simpler than trying to cross over multiple pipes if they are above each other. 

[oranjeboom]

3 hours ago, PeterW said:

An 8 port and a 4 port in tandem will fit with elbow on the corner - that shouldn't need much engineering to fit it and will be simpler than trying to cross over multiple pipes if they are above each other. 

 

Not even sure that would fit. At the moment I have approx 800mm x 400 in the cupboard. Need to ring them and see.

 

Another thought I had was to use the manifold that I will have upstairs (for 2rooms and a hallway) and increase that from a 3port to say a 7 port to feed some of the downstairs rooms. Means I would only need an 8 port manifold downstairs. Main concern would be the extra pressure on the upstairs manifold pump if it's feeding some of the loops downstairs.

[Nickfromwales]

Ok. Thinking cap on ?

Have the pump and blender then a 5 port manifold. Take irons ( brass fittings ) out the ends of both tails, perform a 180 turn and fire back into a 7 port manifold directly in front of the 5. That should stop the second manifold short of the pump bleed screw and leave you enough room to dismount the pump for replacement. 

Get your plumber to use all compression fittings on the flow and return pipework, gate valves as soon as the F&R enters the  cupboard and a drain off cock so you can easily remove the lot in minutes with just a spanner and screwdriver. ?

Sorted.