How far to run 22mm for radiators

[OldKettle]

Hi,
I need to run flow and return pipes roughly 10 metres horizontally, to feed three radiators.

I am going to run 22mm from the boiler, up to the ceiling, across a corridor, into the target room and then down to skirting level. I then need to run 10 metres along the wall, teeing off to the rads as I go.

Should I go the whole 10 metres with 22mm and then tee off with 15mm, or can I get away with 15mm for some of the run?

Any advice would be much appreciated.

EDIT: Each of the rads is approx 3kW

 

[oldbutnotdead]

Check this thread https://www.diynot.com/diy/threads/how-much-heat-42mm-35mm-28mm-22mm-copper-pipe-carry.110733/ - much to my surprise, 15mm COPPER should do it

 

[D_Hailsham]

The normally recommended velocity is 1 m per sec. Given this, the carrying capacity of a pipe depends on the temperature differential across the radiator as this determines the flow rate and, consequently, the velocity.

If it's an old system, the differential is normally about 10C or 11C. In this case, 15mm can carry 6.67kW and 22mm can carry 14.75kW. So you would need 22mm up to the first rad and 15mm for the other two.

If it's a modern system with a condensing boiler designed assuming a 20C differential, 15mm can carry 12kW. So all three could possibly be fed in 15mm from the boiler.

However this all depends on the length of the pipe from/to the boiler as this determines the pressure loss in the run, which has to be within the capabilities of the existing pump.

 

[Hot&Cold]

Is the 22mm mentioned plastic or proper heating pipe ?

Better having good flow rates and then balancing the radiators to provide individual heating requirements,ever property is different

 

[durhamplumber]

Do main runs in 22mm.tee off with 15mm when you reach each radiator..No need for all that delta T,flow /return temperature differential (kelvin of course),water velocity,resistance,pipe diameter squared 4th root of planc's constant bolox.

 

[D_Hailsham]

Do main runs in 22mm.tee off with 15mm when you reach each radiator..No need for all that delta T,flow /return temperature differential (kelvin of course),water velocity,resistance,pipe diameter squared 4th root of planc's constant bolox.

I guess you graduated many years ago from the "watch how Bert does it" school for heating engineers.

 

[OldKettle]

Is the 22mm mentioned plastic or proper heating pipe ?

Better having good flow rates and then balancing the radiators to provide individual heating requirements,ever property is different

I'll be using copper for all the pipework. I wanted to use as much 15mm as I can, partly because of price but mainly because of aesthetics. But performance remains the main concern, of course.

I might eventually chase the pipes, but for now will have them surface mounted.

I have a look through the above, thanks to all. Might possibly do 22mm to the first rad and then 15mm the rest of way (as suggested above) and see how it goes. If it's not good, I have plenty of jobs where I can reuse the 15mm.

 

[durhamplumber]

I guess you graduated many years ago from the "watch how Bert does it" school for heating engineers.

As opposed to the phd in plumbing and electronic control paraphanalia approach now.

 

[bernardgreen]

As opposed to the phd in plumbing and electronic control paraphanalia approach now.

Phds from establishments where the lecturers gained most of their knowledge by research into and analysis of the methods and skills they obtained

from the "watch how Bert does it" school for heating engineers.

 

[Dan Robinson]

You'd be surprised at how effective Bert's rules of thumb can be. It's handy to know all the maths behind for when you have some consultant who thinks he knows everything rinsing the client for ridiculous specs.

Muggins here has a not her meeting for a new project where we have just that. Wonder if this one will throw Ltd at me like the last one, when mass Flow is all that's needed. .

Anyway - not much to add to the posts above in terms of what to do.