ASHP - flow/return

[Kelvin]

Is it ok to run this through the perimeter blockwork then under/within the 75mm screed? 

[MR10]

A question for the ASHP installer maybe? Been told we can install 6" ducting with sweeping bends for the flow/return lines and power cable.

[Kelvin]

Is that within the screed? 

 

They’re a bit slow with the info. We’ve started digging in the ground so a few weeks away from needing to decide how to do it if we go under the slab. 
 

 

[MR10]

Yes, through the blockwork and up/through to the plant room before the 65mm screed is laid 

[MR10]

All theory at this point I should add as we've not started groundworks yet. It'll be interesting to see how you get on with this.

[nod]

If you are using block and beam floors 

You can run any amount of ductings under there and up through the floor 

Last time I ran a couple of 150 ductings But missed one area This time I’ve run four ductings the full length of the house 

[Kelvin]

Strip foundation concrete slab insulation screed. 

[Nickfromwales]

3 hours ago, Kelvin said:

Strip foundation concrete slab insulation screed. 

All the ducts need to be subterranean, and brought up through the slab. I hope you've allowed for at least 150mm of insulation? 200mm is optimum.

Do not run these through such a thin screed, as you'll end up with hot spots and very little residual cover over them ( by the time you fit at least 9mm of Armaflex over them. They'll get significantly warmer when servicing DHW don't forget!

 

Install some pre-insulated pipe for the ASHP, such as...

 

https://pipetek.co.uk/products/32mm-microflex-duo-heating-pipe-kit?variant=29979663466614

 

...which is what I use on almost every ASHP installation we do.

 

You can install this yourself prior to contractors coming in, so you can save some labour here, plus it will be a better job. Bury this at least 400mm deep in the ground if possible. Run 2x 50mm ducts alongside it for 230v power and low voltage signal cables.

[Kelvin]

Yes 200mm

 

So i need one of these 32mm insulated duo microplex pipes and two 50mm ducts. 
 

 

Edited February 19, 2023 by Kelvin

[Nickfromwales]

1 hour ago, Kelvin said:

Yes 200mm

 

So i need one of these 32mm insulated duo microplex pipes and two 50mm ducts. 
 

 

Yup. 

With 200mm you could go in the top face of the lower 100mm layer, with 28mm Hep2o pipe ( run point to point with zero joints in the slab ) and insulate it with 13mm wall Armaflex insulation.

Simple choice is to go under and rise up where required with the Duo. Depends on your multi-tasking skills / sequencing etc, but can be done either way ( just DEFO NOT in the screed ! ). 

[Kelvin]

I’ll go under with the Duo. Thanks for the guidance. 

[Nickfromwales]

1 minute ago, Kelvin said:

I’ll go under with the Duo. Thanks for the guidance. 

👍

[ReedRichards]

6 hours ago, Nickfromwales said:

Install some pre-insulated pipe for the ASHP, such as...

 

https://pipetek.co.uk/products/32mm-microflex-duo-heating-pipe-kit?variant=29979663466614

 

...which is what I use on almost every ASHP installation we do.

 

 

What's the minimum bend radius?

[Nickfromwales]

1 minute ago, ReedRichards said:

 

What's the minimum bend radius?

a good 700mm or more.

[Kelvin]

Just to close this off. The ASHP installer recommended this company to source the insulated dual pipe. Much cheaper than the alternatives at £500 ex VAT for 12m with dust caps and fittings. They deliver UK wide but sort of on my door step so went and collected it. 
 

https://www.flexenergy.co.uk/wp-content/uploads/2022/01/Heat-Pump-Pipe-Kit-10_1_22-_WEB.pdf

 

 

[JohnMo]

I just built my own.

 

2x lengths 110mm convoluted underground duct, left over from build, one length for supply the other for return.  Closed cell 25mm thick pipe insulation, Hep2O barrier pipe inside and aluminium foiled on outside of insulation.  End of duct sealed at both ends at ground level, with stainless steel mesh with closed cell expanding foam (to keep any rodents out).

[Kelvin]

The ASHP installer said to make it up myself but I wasn’t organised enough and groundswork guys wanted it on-site this week. They’ve caught me out a bit on how fast their going! 

[JohnMo]

15 minutes ago, Kelvin said:

They’ve caught me out a bit on how fast their going! 

That's a good compliant to have.

[markocosic]

That duo pipe is terrible; insulation wise. 

 

You want the pir foam stuff rather than the mickey mouse foam. Bending it is even more of a fag though.

 

The ends need to be above ground to keep the insulation dry enough to have value in all versions.

 

I'd do a short length of pipe horizontally through a wall for new builds where the units are right next to the house. (best place for them)

[CalvinHobbes]

What is the best way to make the pipe ourselves? We won't need that much of it. I cannot get over the price!  How do you get PIR down a pipe?

Edited June 18, 2023 by CalvinHobbes

[JohnMo]

18 minutes ago, CalvinHobbes said:

How do you get PIR down a pipe?

You don't, you use a closed cell pipe insulation, such as armacell. 25mm wall thickness will give as good or better than pre made expensive stuff. Then use underground rated pipe or duct to keep it safe.

 

Take you chosen pipe, I used Hep2O 28mm for my 6kW ASHP, add insulation, then insert through duct, I used twin wall 110mm black flexible duct. I made 2 assemblies one supply the other a return rack about 4m long each. 

 

I left a tail of Hep2O pipe out of each end to take up the wall and used a Tectite 90 deg coupler to transition to copper pipe through wall.

 

Seal the end of the underground assembly with stainless mesh or aluminium scouring pads and closed cell spray foam to keep wildlife out.

 

I spent about an hour or so making the 2 pipes.

[markocosic]

The pukka stuff (e.g. series 2 insulated rehau) will last longer with lower heat loss. Pig to work with though.

 

Armacell on 28 mm Hep2o is adequate if you can be sure of the duct remaining dry (not below water line with a slight nick to duct or "U" shaped with exposed ends etc - heat loss from pipe will tend to dry residual moisture for most setups)

Edited June 18, 2023 by markocosic

[haythorn_1]

If doing strip foundations would the pre-insulated pipe need to go below the footing? If so how far below? Must need a deep trench! 

[JohnMo]

3 minutes ago, haythorn_1 said:

If doing strip foundations would the pre-insulated pipe need to go below the footing? If so how far below? Must need a deep trench! 

Really depends on location of heat pump and plant room or cylinder location. If you just can go through the wall two holes in wall - done.

[haythorn_1]

Plant room is about 5m from ASHP location. So could run pipes in the ceiling joists to the exterior wall or below the foundations. 

 

Through the foundations seems much more expensive but I guess it removes the need for a wall penetration.