ASHP pipework

[yoclick]

Hello all, 

 

Firstly nice to join the forum. 

 

Im doing a fair bit of renovation now in prep for a rear double story extension I'd like to do in a year or 2. I would like to install an ASHP eventually after extending so just want to future proof myself now while I have the chance. 

 

I estimate the house need is 8kw currently and c. 15kw post extension. 

 

Im looking to install 28mm pipe from boiler to hot water cylinder, and then 28mm from there to centre of house, then teeing to 2x 22mm feeding each side of the existing house and then 15mm at rads. All in copper. The reason for not running 28mm all the way is a steel RSJ getting in the way. 

 

When the extension is done, I fully suspect BC will request it to be a seperate zone. I was planning to run 28mm from water cylinder teeing to 22mm for upstairs and 22mm downstairs. 

 

Any thoughts, concerns or advice? 

 

Edited October 19, 2023 by yoclick

[marshian]

9 minutes ago, yoclick said:

Hello all, 

 

Firstly nice to join the forum. 

 

Im doing a fair bit of renovation now in prep for a rear double story extension I'd like to do in a year or 2. I would like to install an ASHP eventually after extending so just want to future proof myself now while I have the chance. 

 

I estimate the house need is 8kw currently and c. 15kw post extension. 

 

Im looking to install 28mm pipe from boiler to hot water cylinder, and then 28mm from there to centre of house, then teeing to 2x 22mm feeding each side of the existing house and then 15mm at rads. All in copper. The reason for not running 28mm all the way is a steel RSJ getting in the way. 

 

When the extension is done, I fully suspect BC will request it to be a seperate zone. I was planning to run 28mm from water cylinder teeing to 22mm for upstairs and 22mm downstairs. 

 

Any thoughts, concerns or advice? 

 

How big is the extension to double the heat loss and yet comply with current building regs as far as build structure and insulation is concerned!!!!

[yoclick]

Just over doubling the size of the original house

Edited October 19, 2023 by yoclick

[nod]

Don’t forget to insulate all the 28 mil

[ReedRichards]

7 hours ago, yoclick said:

Just over doubling the size of the original house

 

Even so, can you not ensure that the insulation standard is good enough that you don't double the heating requirement of the house?  

[JohnMo]

If you really need a 15kW, which I very much doubt, unless you are doing a very poor quality build that doesn't comply with any regs. Then 28mm is way too small for a heat pump primary piping.

 

Go on the heat geek site, they have section on heat pump pipe sizing, which should give a good steer.

 

[Marvin]

Hi @yoclick

 

Plus one on all the advice above.

 

I would do some research to confirm the location of the future ASHP. Its not just the water pipes to be considered; will your electricity supply and cabling handle the load to the same destination?

 

In principle it is best to have the ASHP unit as close as possible to the hot water tank/heat sump/buffer tank (length of pipe wise), you should have any hot water storage all within the thermal envelope of the building, all external pipework needs to be insulated to within an inch of its life. Yes the system will work if you don't do these, but the system will run less efficiently until its replaced or improved.

 

Good luck

 

M

[yoclick]

Thanks all. Some additional information so you can have some comfort I havent plucked figures out of thin air:

 

1) House is 130sqm, 1950 but renovated so using 60w/sqm (higher end of heat geeks cheat sheet) gives circ 8kw.

 

2) Extension will be ab additional 160sqm at 40w/sqm (again, higher end) gives 6.5kw.

 

3) Total is 14.5kw rounded to 15kw. Again I recognise I've added a rounding buffer to already other buffers.

 

4) 28mm pipe using heat geek cheat sheet is slightly worse than dt7 at 15kw. Not ideal but with the buffers above I reckon it will be around or better than dt7 in reality. 

 

5) Obviously 22mm is therefore not sufficient but as stated in my OP, my plan is to T the 28mm after the water cylinder. 

 

6) Water cylinder and ASHP will be within 4m of eachother, with the pump 1m within the external wall.

 

So key for me in my understanding of point 5 as I'm doing some 22mm piping now and want to ensure I'm going to cause a problem later on. 

 

Thanks! 

[yoclick]

Hi all, 

 

Any thoughts before I proceed? 

 

Thanks 

[TonyT]

Seek structural Engineer to get permission to drill steels to utilise larger pipes and not compromise design

[yoclick]

Thanks, but does splitting the 28mm to 2x 22mm create an issue? Per heatgeeks guidance, permitted load is spread evenly it seems it could be fine but not understanding the hesitation from the forum? 

 

I'd rather that then drill the steels especially since it would mean deeper notches on floor joists either side (most likely outside of regs compliance) as you won't be allowed to drill above central line.