Copper vs Plastic for ASHP flow/return

[doyled]

Wondered on views on copper vs plastic for the following situation.

 

I'm wanting to put in some pipework to prepare the house ready for a future ASHP installation. The ASHP and cylinder would be placed at the front of the property in the lower ground floor with a run of 7 metres or so back to the water riser at the back. I believe there would thus be 3 pipes required - 1 x DHW, 1 x heating flow and 1 x heating return.

 

The pipework would be in the lower ground floor kitchen, running front-back in the ceiling void. Putting in the pipework now is useful as the ceiling plasterboard is down due to refurbishment. Makes great sense to run the pipework now so it's hidden away later.

 

My ASHP engineer said to put in 22mm copper for all 3 pipes, insulated with 19mm Armaflex. My builder has issues with that, saying that as copper is only in 3m lengths there would be several joins and he has concerns for future servicing with it being in the ceiling. He also says that as there are other obstructions in the void (the ceiling is suspended from battens attached to the joists but there are some obstructions) that having "PVC barrier pipe" instead would make more sense and enable him to negotiate around potential obstacles in the void if needed. He's said 22mm plastic is the same as 22mm copper but having looked online (https://heatpumps.co.uk/pressure+flow/simulator.html) I know that the internal bore would be reduced with plastic, plus with smoothness issues.

 

I'm feeling rather piggy in the middle - my view is that if the ASHP engineer says we should run 22mm copper then that is what we should run. If not then I think we'd need to run 28/32mm plastic instead to make up for the reduced bore. I'm not convinced that plastic is the right choice.

 

Unfortunately the only contact I have at the ASHP provider is the sales person who is difficult to get in contact with. The engineer came to site but my builder was not there at the same time. I don't want to have to keep trying to go between the two. If copper is the best option then I'll direct that to be used.

 

Thanks,

 

David.

 

 

[TonyT]

28mm hep20 for me, less joins less likely to create a future problem.

 

 

[jack]

We have 28mm Hep2O connecting our ASHP to our plant room over a ~9 metre distance. All done without a single join, which in our case would have been a massive pain given a lot of it is in a channel cut through our underfloor EPS. 

 

Hep2O barrier pipe includes an oxygen barrier and is specifically designed for this sort of application, so I can't what the objection would be to its use - from https://blog.wavin.co.uk/all-you-need-to-know-about-hep2o-push-fit-plastic-plumbing-pipe/:

 

[SuperPav]

I will most likely be installing a UVC with buffer tank, running off a gas boiler in the short term, but with the intention of at some point in the future switching over to ASHP.

 

I'm going to pre-run the pipes to the cylinder from the location where the ASHP eventually would go, in 28mm Hep2o. 

[JohnMo]

You can run all your pipes in plastic barrier pipe, except within 1m of the boiler or hot water cylinder.

 

You could also leave the gas boiler there, as a fall back if you have maintenance ongoing on the ASHP, or in very cold weather when the cop is less than ideal.  A hybrid system.

[Roger440]

I admire all you chaps faith in plastic.

 

Its not shared.

[JohnMo]

4 minutes ago, Roger440 said:

I admire all you chaps faith in plastic.

 

Its not shared.

Any reasons?

 

Assume you don't have UFH

[Roger440]

Well, ive just installed some. But i was referring to above ground. But the UFH has an aluminium liner.

 

Why. Degredation and pipes popping apart. Been the victim of the latter. Never had a soldered joint "pop apart".

 

I simply dont believe plastic pipes subject to heat cycling will last like copper does. Which is essentially a lifetime.

Edited February 4, 2022 by Roger440

[Dan F]

We used a single length of pre-insulated Rehau Rauthermex duo for this.  It was 8-10m and we took it down thorugh the slab, under EPS and then up in the ASHP install location.

Edited February 4, 2022 by Dan F