Running ASHP feeds to outbuilding

[d438a1]

Hi there, 

 

I'm looking at getting a heat pump installed this year and as part of it I'm provisioning to run feeds to a new outdoor workshop which will have underfloor heating in slabs. Based on my house and this, seems like consensus is a 16kw ASHP. 1 or 2 that have quoted so far just said to run 28mm insulated pipe from house plant room to new workshop (circa 15m).

 

I've already got a trench dug for other reasons so want to lay it now in readiness. Is something like this ok in either 25 or 32mm?

 

https://www.plumb2u.com/32mm-pre-insulated-mlcp-pipe-25m-coil-red-palpex-32025r-c2x41327360

 

Thanks

[d438a1]

I should add the trench will be circa 700mm deep as also running cold mains water. 

[JohnMo]

The insulation thickness looks pretty poor. I would be looking for 25mm insulation minimum.

 

You need to do pipe sizing based on pressure drop. So you need to know the kW required for the workshop. Then the flow rate can be calculated and pressure drops.

 

But some comments on your proposed scheme I do something similar with a summer house.

 

We did 28mm Hep2O, 25mm closed cell insulation, wrapped in foil tape (mice don't like it) then inserted in 110mm flex drainage pipe. Sealed ends as it came out of the ground with stainless mesh and spray foam. Cheap easy enough, everything available locally, so no transport costs.

 

 

[d438a1]

Thanks for reply. When you say 25mm close cell insulation, what do you mean?

[JohnMo]

12 minutes ago, d438a1 said:

Thanks for reply. When you say 25mm close cell insulation, what do you mean?

Something like this

https://www.wolseley.co.uk/product/armaflex-evo-tube-selfseal-armaflex-evo-tube-selfseal-1-1-8-od-x-1-wt/

[Nickfromwales]

7 hours ago, d438a1 said:

Is something like this ok in either 25 or 32mm?

Have you seen this type of product?

 

https://www.advancedwater.co.uk/product/20m-microflex-25-2-3mm-insulated-underground-pipe-pack-md12525cpack20

[Dreadnaught]

Beware the bending radius's of fat python-like insulated double pipes! If I had my time again, I'd probably go with a pair of insulated single pipes because of it.

[Kelvin]

10 minutes ago, Dreadnaught said:

Beware the bending radius's of fat python-like insulated double pipes! If I had my time again, I'd probably go with a pair of insulated single pipes because of it.

A good point. We had to go quite deep with our pipe to get a suitable bend radius. 
 

Why not fit an Air2Air heat pump instead? Far simpler than extending your house ASHP and will likely work better for an occasionally used outbuilding. 

[d438a1]

Thanks for replies. The outbuilding will be around 8m x 5m. And was planning on doing underfloor heating in slab. I was also future proofing a little incase someone in future uses building for any other purpose than a workshop