Any use in using 22mm pipe?

[Roz]

I'm sorry because I know this has been asked in various forms before but it's difficult to apply the answers if your situation is a bit different to the original question! So I'll try to be quick

We've got incoming 25mm MDPE from 80m distance down to the mains. 

We're going to be using a Telford Heat Pump cylinder pre heated by the ASHP

ASHP will heat UFH directly

Pretty small house

 

I'm about to start running the general bits of the plumbing, leaving the tank and the ASHP and UFH manifold for a plumber.

 

Should I use 15mm everywhere, or have the main backbone of the plumbing in 22mm and tee off in 10mm or 15mm for everything except the shower and bath? 

 

Thanks!

 

 

Edited May 28, 2020 by Roz

[ProDave]

I used 15mm for everything including the showers and the bath, to minimise volume of water until hot reaches the tap.  No problems with flow rates.  What is your mainspressure and flow like? that is what will drive it.

 

But do make sure heating loops from ASHP to manifolds and HW tank are large and short.  ASHP's in general seem to like high flow rates and I had to fit a second pump to get a high enough flow rate through the 22mm pipework.  28mm would haqve been better.

[Roz]

5 minutes ago, ProDave said:

I used 15mm for everything including the showers and the bath, to minimise volume of water until hot reaches the tap.  No problems with flow rates.  What is your mainspressure and flow like? that is what will drive it.

 

But do make sure heating loops from ASHP to manifolds and HW tank are large and short.  ASHP's in general seem to like high flow rates and I had to fit a second pump to get a high enough flow rate through the 22mm pipework.  28mm would haqve been better.

I haven't really looked into the ASHP yet so sorry if none of this makes sense but... so I should fit a 28mm hep2o pipe from the incoming 25mm MDPE to the ASHP, and then from there to the manifold and to the tank? I'm not going to do the actual plumbing for the ASHP or manifold but I will put the long pipe runs in place. The runs will be between 4-8m between tank and ASHP, and cold mains and ASHP

I am not really sure what the mains pressure is like, I will check it from the outside tap we've got fitted... although that is reduced down to 15mm so not sure how that affects it. What is a good flow rate anyway? I will try to measure it tomorrow.

[Roz]

Also the plan is to use a DAIKIN EDLQ05CV3 5KW SMALL MONOBLOC

[PeterW]

22 to the UVC. 22 from UVC to manifold. 15mm to shower / bath from manifold. 10mm elsewhere. 
 

22 or 28 for the ASHP depending on MIs

[Roz]

11 hours ago, PeterW said:

22 to the UVC. 22 from UVC to manifold. 15mm to shower / bath from manifold. 10mm elsewhere. 
 

22 or 28 for the ASHP depending on MIs

Thanks Peter. What is MIs? I've tried looking at online manuals for the ashp but can't see the pipe size.

[DavidFrancis]

Pretty sure he means "Manufacturer's Instructions".

[PeterW]

MIs is the Manufacturers Instructions. How far from the tank to the ASHP..? TBH if it is only 5kw then 22mm should be fine anyway.

[Roz]

16 hours ago, PeterW said:

MIs is the Manufacturers Instructions. How far from the tank to the ASHP..? TBH if it is only 5kw then 22mm should be fine anyway.

I can't seem to find the information online when searching things available to download. It's 3.5m horizontally and say 3 metres vertically between the two! So roughly a 6.5m run

[ProDave]

I

37 minutes ago, Roz said:

I can't seem to find the information online when searching things available to download. It's 3.5m horizontally and say 3 metres vertically between the two! So roughly a 6.5m run

I have roughly 25M in total of 22mm pipe in the ASHP circuit and I could not achieve the required flow rate just with the pump built into the ASHP. I had to fit a second external pump to get the flow rate high enough for the ASHP.