ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Shout Box
Recent Posts
IRC M1307.3
by gfretwell. 08/18/18 09:08 AM
Light Pole Grounding
by Mosfet74. 08/18/18 08:42 AM
Calling all Non-US members!! (Non-US only)
by Bill Addiss. 08/13/18 05:52 PM
Upgrade the old panel
by gfretwell. 08/13/18 12:20 AM
depth of duckbank
by ghost307. 08/12/18 09:26 PM
New in the Gallery:
Plug terminals
Housebilding DIY wiring
Who's Online Now
0 registered members (), 5 guests, and 25 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Ch9 table 1 #193048
03/17/10 02:24 AM
03/17/10 02:24 AM
Niko  Offline OP
Member
Joined: Aug 2006
Posts: 356
Campbell, CA
Table one of Ch 9 says if we have one conductor we can fill the conduit to 53%, 2 conductor to 31% and more than 2 conductors the conduit can be filled to 40%.
My question is why 31% for 2 conductors and 40% for more than 2 conductors? what is rational behind it.

An IAEI instructor once told me it is because of the heat dissipation. But he did not explain in details why?

Thanks.


Be kind to your neighbor, he knows where you live

2017 / 2014 NEC & Related Books and Study Guides
Re: Ch9 table 1 [Re: Niko] #193049
03/17/10 02:41 AM
03/17/10 02:41 AM
G
gfretwell  Online Content

Member
Joined: Jul 2004
Posts: 9,252
Estero,Fl,usa
It just has to do with how they pack into the pipe. Three takes up less room than 150% of 2 and it is volume we are speaking of.
Heat really doesn't enter into it. You derate "x" number of conductors the same no matter what size pipe it is in.


Greg Fretwell
Re: Ch9 table 1 [Re: gfretwell] #193053
03/17/10 10:14 AM
03/17/10 10:14 AM
R
Rewire  Offline
Member
Joined: Feb 2008
Posts: 165
Missouri
ask your instructor to elabroate.Then come tell us.

Re: Ch9 table 1 [Re: Rewire] #193057
03/17/10 04:44 PM
03/17/10 04:44 PM
Niko  Offline OP
Member
Joined: Aug 2006
Posts: 356
Campbell, CA
Rewire,
the instructor was at a seminar. so i don't have access to him anymore.

I have posted the same question at Mike's site http://forums.mikeholt.com/showthread.php?t=123904
but i am still not 100% confident on my understanding.


Be kind to your neighbor, he knows where you live

Re: Ch9 table 1 [Re: Niko] #193059
03/17/10 08:23 PM
03/17/10 08:23 PM
T
Tesla  Offline
Member
Joined: Jun 2004
Posts: 1,273
Sacramento, CA
It's the radius of the conductors...

Do the math.

It boils down to the straight geometry of circles.

The conduit/EMT is the big circle...

Now how many circles can you fit inside leaving enough room to pull in without excessive force/ruining the insulation.

That's all that's involved.


Tesla
Re: Ch9 table 1 [Re: Tesla] #193061
03/17/10 09:26 PM
03/17/10 09:26 PM
R
Rewire  Offline
Member
Joined: Feb 2008
Posts: 165
Missouri

Last edited by Rewire; 03/17/10 09:27 PM.
Re: Ch9 table 1 [Re: Rewire] #193076
03/18/10 01:44 PM
03/18/10 01:44 PM
S
sabrown  Offline
Member
Joined: Dec 2002
Posts: 302
Ogden, Utah, USA
Expounding on Tesla, 3 conductors can line up in a straight line so all the diameters add up. 4 or more and bundle collapses (the conductors don't ever twist up to line out in a row. Thus the binding issue for 3 conductors.

Re: Ch9 table 1 [Re: sabrown] #193122
03/19/10 09:32 AM
03/19/10 09:32 AM
R
Rewire  Offline
Member
Joined: Feb 2008
Posts: 165
Missouri
just when it all makes sense they bring in nipples


Featured:

2017 Master Electrician Exam Preparation Combos
2017 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Member Spotlight
Samurai
Samurai
Fl.
Posts: 46
Joined: May 2007
Show All Member Profiles 
Top Posters(30 Days)
BigB 3
Popular Topics(Views)
248,605 Are you busy
186,342 Re: Forum
175,802 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.6.1
(Release build 20180101)
Page Time: 0.020s Queries: 15 (0.004s) Memory: 0.9933 MB (Peak: 1.1547 MB) Zlib enabled. Server Time: 2018-08-18 16:24:36 UTC