UFH - Supply and Return pipes...

[JohnMo]

2 hours ago, Mulberry View said:

I've raised concern about heat striping

Depends on the depth of pipes, ours are in 100mm screed and there is zero.  So thats should not be a concern.  Even when I used the boiler at 34 degs there were none. 

 

300mm is generally fine, one thing it does bring is a fall off of heat transfer at very low flow temps, so to counter that on 7 to 10 deg days I just flow at 29 and in Cosy periods and the runs are good.  Have a WC curve that runs 29 to 32 (10 degs to -5 degs).  Running 29 degs gives a very stable run time of over 3 hours and also excellent CoP, just finished a run I did as I was getting free electricity, ran in manual for 3 hours and got a CoP average of 6.6 at one point it was doing over 7.

 

2 hours ago, Mulberry View said:

but I am minded to want closer pipe spacing as I'd prefer some headroom

At 300mm spacing you can very easily hit very high room temps, just flow too high for too long and you go into melt down.  Just use the chart I posted on 30 Aug to work out how little flow temp increase you need to add to increase output hugely.

 

If you are concerned just drop the spacing to 200-250mm, but tighter in bathrooms due to the limited floor area

 

[Mike]

5 hours ago, Mulberry View said:

The designer has gone for 300mm pipe centres

FWIW, French regulations specify a maximum of 250mm between pipes - more here:

 

 

Edited Friday at 18:10 by Mike

[Andeh]

300mm pipe spacing does seem big, on tile flooring you'll notice the heat spacing unless you have really thick screed.

 

Id opt for smaller and dial back the temp.

[Mulberry View]

So, back to the original point, Supply and Return pipes to/from the manifolds. What type of pipe is best to use here? I'm installing 25mm (26mm?) that will be within the PIR, with 150mm PIR under it. There is about 30m of linear length to reach both manifolds, so I'll need 60m of pipe in total, which I understand needs to be insulated despite it being installed into PIR? Is it just 25mm Pre-insulated MLCP?

 

As for the design, the designer was certain that 300mm spacing would meet the heating requirements, but I've had him do 200m spacing to be on the safe side (150mm in the Bathroom). I don't really ever want to do this again and certainly don't want to have to use plug-in heaters if it gets chilly!

 

There are 2 manifolds as this simplified the routing. The M3 manifold is at the lowest ground floor level, the M1 manifold is 1m higher in terms of ground floor FFL. The bundle of pipes running along the hallway to the WC and Utility will be in conduit as they are just transit pipes and the heat they emit is not required before the rooms.

 

This design saves 400m of pipe compared to the earlier designs. The ASHP will be against the wall in the top-right of this drawing, so the manifold connections are the hardest part here really.

 

[JohnMo]

I would do it in 28mm hep2o, zero issues with noise or pressure drop. You maybe would be ok with 22mm but for the cost difference just cover all basis. 

 

16 minutes ago, Mulberry View said:

The bundle of pipes running along the hallway to the WC and Utility will be in conduit as they are just transit pipes and the heat they emit is not required before the rooms.

 

You can do it that way, and that's the way you would do it if you are running every area on its own thermostat, but are you? Sounds like a waste of pipe and conduit to me.

 

19 minutes ago, Mulberry View said:

which I understand needs to be insulated despite it being installed into PIR?

 

Insulation on pipes when run inside PIR - what is the insulation doing that the PIR isn't doing already? no idea why you need the additional insulation.

[Mulberry View]

19 minutes ago, JohnMo said:

I would do it in 28mm hep2o, zero issues with noise or pressure drop. You maybe would be ok with 22mm but for the cost difference just cover all basis. 

 

 

You can do it that way, and that's the way you would do it if you are running every area on its own thermostat, but are you? Sounds like a waste of pipe and conduit to me.

 

 

Insulation on pipes when run inside PIR - what is the insulation doing that the PIR isn't doing already? no idea why you need the additional insulation.

 

The insulation thing intrigued me too. I asked AI, which told me that PIR is great at stopping heat from travelling downwards, but isn't so good at preventing it travelling sideways through the PIR boards and that the sleeving on the MLCP pipes somehow performs differently! Who knows. Not me that's for sure.

 

I do know that I have to be able to create 90° bends halfway along the pipes, to transition as needed without fittings.

 

[saveasteading]

It's not as difficult as you seem to think, and AI seems to be telling rubbish.

 

No 90°corners: it easily curves 90 or 180.

Fitting with insulation above it is just wrong. You can set it on top then screed it, or put it in special floorboards. Or painstakingly depress it into the pir. Or use eps as a top layer as I think you could tread it in. What floor finish will you have?

Ducts are not only unnecessary but counterproductive. The 'highways' as they seem to be called are both flow and return, so it is not all at peak temperature.

 

Norwich is too far, but anyone in SSE is welcome to some of the huge amount of oversupply of pipes we were specified, I think 40 to 60m long. Not insulated, as they should not be except your short run from heat pump to manifolds.

 

 

[JohnMo]

Where are your flow and return pipes running to and from - do you have a route planned?

[Mulberry View]

1 hour ago, JohnMo said:

Where are your flow and return pipes running to and from - do you have a route planned?

 

This is them sketched by me on an earlier layout plan. Ignore the pipe layout and manifold positions on that plan, this was an overlay to show my proposed position of the M1 manifold and the omission of the M2 manifold in the middle, along with routing of the supply/returns.

 

Where the omitted manifold is shown there, the supply/returns need to turn up out of the lower floor, ascend by 600mm then turn back into the Kitchen floor. The 600mm vertical section will need to be contained in a battened out wall.

 

Edited 4 hours ago by Mulberry View
Added the attachment. Duh.

[JohnMo]

So question, instead of through the house, why not around the house, buried in trench then though wall to manifold.  Would certainly do the manifold in room M1.2 in 28mm.

 

Are you intending to run as a single or 2 zone system?

[Mulberry View]

1 hour ago, JohnMo said:

So question, instead of through the house, why not around the house, buried in trench then though wall to manifold.  Would certainly do the manifold in room M1.2 in 28mm.

 

Are you intending to run as a single or 2 zone system?

 

How would running these pipes around the house benefit? I can't see how it would shorten or simplify the routes unless I've missed something obvious?

[saveasteading]

1 hour ago, JohnMo said:

why not around the house, buried in trench 

Heat loss would be greater unless using  the horrendously expensive pipes made for the purpose. Even then, indoors would be less wasteful of the heat.

We used 2 layers of insulation and cut them into the lower one.

 

 

[JohnMo]

2 hours ago, Mulberry View said:

 

How would running these pipes around the house benefit? I can't see how it would shorten or simplify the routes unless I've missed something obvious?

I thought you had elevation changes to contend within the house, thought it maybe easier routing overall outside Or just route them beside the UFH pipes, why bother insulating at all inside the heated environment, any heat loss is going into the house.  In cooling mode atmospheric air is excluded, so no condensation to make either. Assume your hot water cylinder is in room M3.4? If so why are you bothering with an UFH loop in that room? It's always going to be warm, ours sits in an unheated loft space room is 6m x 4m it's always the warmest place in the house.

[Mulberry View]

21 minutes ago, JohnMo said:

I thought you had elevation changes to contend within the house, thought it maybe easier routing overall outside Or just route them beside the UFH pipes, why bother insulating at all inside the heated environment, any heat loss is going into the house.  In cooling mode atmospheric air is excluded, so no condensation to make either. Assume your hot water cylinder is in room M3.4? If so why are you bothering with an UFH loop in that room? It's always going to be warm, ours sits in an unheated loft space room is 6m x 4m it's always the warmest place in the house.

 

You didn't read what I wrote alongside that pic! LOL.

 

Regarding the internal level changes, they are also outside, we have a tricky plot and an even trickier shaped building. They need to be inside really.

[Mulberry View]

1 hour ago, saveasteading said:

Heat loss would be greater unless using  the horrendously expensive pipes made for the purpose. Even then, indoors would be less wasteful of the heat.

We used 2 layers of insulation and cut them into the lower one.

 

 

 

How did you go about cutting them into the lower one?

 

I have 150mm PIR already laid. My plan was to lay the supply/returns, then add the top layer of PIR around and over the pipes. It felt like it'd be easier than trying to carve channels in the already laid layer?