Pipe sizing - Replacing a one pipe system with flow and return

[Fwds2andback]

Hi,
I'm a first time poster with a skill set akin to that of a competent DIY'er I guess. I'm planning on replacing a old in efficient one pipe system with a flow and return. This will be done on our recently purchased bungalow which has an oil fired boiler. Whilst I'm confident a 22mm flow and return with 15mm T's for the 15 radiators will be sufficient in terms of heat carrying capacity, I'm concerned that the flow resistance posed by the long pipe runs will be excessive. I was therefore wondering if the entire flow and return down the centre of the house should be run in 28mm? The boiler is approximately 8m 50 from the spine of the house where a 14m flow and 14m return will run. Hopefully the plan below shows the layout in sufficient detail.

I'd be grateful of any advice this forum could offer, thanks!

 

[tamzbackforalook]

How far would you like me to go in-depth most of the time it’s lost on a diyer so tend not to confuse them

Fill your boots. I'd be interested to see if you are learning

 

[ShaunCorbs]

Well 22mm can carry 0.29lps which works out to around 24kw at dt20 with a 0.9mps flow rate

28mm will carry 0.49lps which works out to around 40kw at dt20 with a 0.9mps flow rate

Now with England recommending you start sizing your Emitters for a flow of 50dc eg dt20 rads eg ready for heat pumps your pipework needs to be sized the same

For example

22mm will carry 6kw with a dt 5 on water and 5.4 on gycol
28mm will carry 10kw with a dt 5 on water and 9.2 on gycol

 

[tamzbackforalook]

Well 22mm can carry 0.29lps which works out to around 24kw at dt20 with a 0.9mps flow rate

28mm will carry 0.49lps which works out to around 40kw at dt20 with a 0.9mps flow rate

Now with England recommending you start sizing your Emitters for a flow of 50dc eg dt20 rads eg ready for heat pumps your pipework needs to be sized the same

For example

22mm will carry 6kw with a dt 5 on water and 5.4 on gycol
28mm will carry 10kw with a dt 5 on water and 9.2 on gycol

Keep going

 

[ShaunCorbs]

Keep going

For that I would need pipework lengths / runs and emitter loadings which op doesn’t state and tbh not worth it on a free forum your more than welcome to spend your time on it though and send a full report to the op eg emitter sizing and pipe pressure losses/ pump head required etc 👍

 

[tamzbackforalook]

Can't be bothered but you should change your numbers on your calculating base.
But what do i know. I'm retired😉

 

[tamzbackforalook]

How many boilers come with 28mm F&R these days and water is not compressable?

 

[ShaunCorbs]

How many boilers come with 28mm F&R these days and water is not compressable?

Same as why most heat only come with 15mm gas doesn’t mean I can run it straight from the meter in 15mm 20m etc (at 15kw)