ASHP pipework

[Triassic]

I’m going to install an ASHP, no idea which one, but around 6kw in size. What size pipe work do I need 15 or 22mm?

[ProDave]

22mm minimum.  Most are VERY sensitive to flow rate and require quite a high flow rate, I had to fit a second pump to mine to satisfy it. So there is an argument if a long run for going up to 28mm.

[PeterW]

Always go 22mm to a heat source - 28mm is even better for long runs however you may need to check the heat pump connections. I know the last couple I’ve seen have 1” or G1 connections so 1” to 28mm is possible but looking inside the units the pipework to the heat exchangers are only 15mm. 
 

 

[Triassic]

It’s about 15m run out to the ASHP and 15m return.

[Dreadnaught]

Following with interest as I am thinking of a similar long run. Pre-insulated pipes?

[Triassic]

My pipes run inside the house, do they need insulation?

[ProDave]

Yes, otherwise it will add unwanted heating in the house when just trying to do DHW in the summer.

[Conor]

The installation manual will specify... From what I've seen from Mitsubishi etc, all seem to have 22mm connections. Yes, fully insulate the full pipe runs.

[ADLIan]

Requirement for pipe insulation is covered in Appr Doc L1A and the Domestic Building Services Compliance Guide

[tommyt]

Also interested in this thread as we have just moved plant room location on our plans to the front of the attached garage but need to keep heat pump in same location at back and will run pipes through. 

[Dan F]

Just had this discussion with M&E consultant yesterday.  He has suggested using 3 seperate ducts rather any more innovative Uponor products just to ensure as much flexibility as possible. Unsure exactly what duct is proposed though, currently allowing 3x75mm ducts.

 

In our case ASHP will be about 6m away.  I've seen some people take duct through EPS, but thinking we'll probably just use a pre-insulated pipe and take it under EPS.

[Dan F]

These are our pre-insulated pipes put in below the sub-base.  3 x REHAU RAUTHERMEX 25mm+25mm/111mm DUO PIPE

 

[Nick Laslett]

Hello Gents,

 

Need some help, what size pipe do you think I need?
 

ASHP manual spec

Water supply/return Ø R 1 1⁄4”

Use Rp 1 1⁄4" nut for both water inlet and water outlet connection

 

There are two insulated pipes in the Uponor catalogue 

Uponor Ecoflex Thermo Twin

External diameter 32mm, internal diameter 25mm

or

External diameter 40mm, internal diameter 32mm

 

https://www.underfloorstore.co.uk/product/uponor-ecoflex-thermo-twin-pre-insulated-pipe

 

I need about 8m of pipe

 

Edited April 8, 2021 by Nick Laslett

[Dreadnaught]

(@Nick Laslett, I might have about 8m of the 32mm insulated twin pipe spare on my site if you're interested. I'll measure the off-cut next time I'm there.)

[Trw144]

I would recommend using the fully bonded closed cell type of pipe (Calpex from Brugge or Rehau Rauthermex rather than the "onion" layer types such as Uponor (in the event of the latter, any damage to the outer casing can lead to water ingress along the pipe).

Edited April 8, 2021 by Trw144

[Meabh]

On 29/06/2020 at 17:18, Dan F said:

These are our pre-insulated pipes put in below the sub-base.  3 x REHAU RAUTHERMEX 25mm+25mm/111mm DUO PIPE

 

Hi - how deep did you have to go (and across what distance) to get the pipes like this? Thanks

 

[Dan F]

2 hours ago, Meabh said:

Hi - how deep did you have to go (and across what distance) to get the pipes like this? Thanks

 

This is directly related to the min bend radius of the product you are using.   Rauthermex Duo is 0.6m, which means that if you want the pipe to be vertical up through the concrete slab you need to go 0.6m below this. 

[gavztheouch]

Hi I am planning on using arotherm plus 5kw Ashp. Thinking about using Rauthermex Duo or similar to pipe water into building. Not sure what size I should use or how to even figure it out. What I've done so far is look at the connection size of the 5kw model, which is 1 1/4, so 32mm, but the 12kw model with a higher flow rate also uses the 32mm connection so its possible the 5kw does not need a 32mm connection and the 25mm will be fine. The 25mm is slightly cheaper and has a better heat lose value. There would also be less water sitting inside the pipe getting cold between cycles which in a low energy house where it might cycle a lot on and off throughout the day this could be significant. 

[JohnMo]

If you back to basics, you need to get the circulation pump duty point, and know what the acceptable pressure drop is. You work back from that, so you need to know distances and what bends you will have and the pressure drop per metre and per bend and also any pressure drops through valves.