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#193048 - 03/17/10 02:24 AM Ch9 table 1  
Niko  Offline
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


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#193049 - 03/17/10 02:41 AM Re: Ch9 table 1 [Re: Niko]  
gfretwell  Offline


Member
Joined: Jul 2004
Posts: 9,060
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

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


#193057 - 03/17/10 04:44 PM Re: Ch9 table 1 [Re: Rewire]  
Niko  Offline
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


#193059 - 03/17/10 08:23 PM Re: Ch9 table 1 [Re: Niko]  
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

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

Last edited by Rewire; 03/17/10 09:27 PM.

#193076 - 03/18/10 01:44 PM Re: Ch9 table 1 [Re: Rewire]  
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.


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



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