View Single Post
  #5   Report Post  
Posted to uk.d-i-y
John Rumm John Rumm is offline
external usenet poster
 
Posts: 25,191
Default How do I calculate gas pipe size?

Toby wrote:

From memory, an elbow counts as an equivalent length of 0.5m of pipe,
and a bend as 0.3m equivalent. So if you have five meters of pipe with
two bends, then that is an effective length of 5.6m.


Okay, thanks for that, on reading the link, you are quite correct, an
elbow is 0.5m and a bend is 0.3m.

The boiler is a Vaillant EcoTEC 837, which is 37Kw. According to the
manual needs up to 4M3/hour


Well if you take a m^3 of gas as 38.2MJ, then 37kW will require 133 MJ/h
or 3.5 m^3 ish. So 4 sounds like a generous top limit to work to.


If I am understanding this correctly, a 6m run of 22mm will give me 5.8
m3/h at 20mbar, so that's going to be fine. Even if the length was 9m,
the delivery would be 4.6M3/h at 20mbar, so I am well within tolerance
here.


Yup, that sounds plausible. When I did my boiler it was 35kW and IIRC
the max run of 22mm I calculated I could use was 12m. In reality I only
needed 6, which I did in mostly 22 and only dropped to 15 at the union
on the boiler. Dynamic pressure was fine.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/