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#193048 - 03/16/10 11:24 PM Ch9 table 1
Niko Offline
Member

Registered: 08/17/06
Posts: 358
Loc: 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.
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#193049 - 03/16/10 11:41 PM Re: Ch9 table 1 [Re: Niko]
gfretwell Offline


Member

Registered: 07/20/04
Posts: 9062
Loc: 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.
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#193053 - 03/17/10 07:14 AM Re: Ch9 table 1 [Re: gfretwell]
Rewire Offline
Member

Registered: 02/23/08
Posts: 167
Loc: Missouri
ask your instructor to elabroate.Then come tell us.

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#193057 - 03/17/10 01:44 PM Re: Ch9 table 1 [Re: Rewire]
Niko Offline
Member

Registered: 08/17/06
Posts: 358
Loc: 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.
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#193059 - 03/17/10 05:23 PM Re: Ch9 table 1 [Re: Niko]
Tesla Offline
Member

Registered: 06/16/04
Posts: 1280
Loc: 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.
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#193061 - 03/17/10 06:26 PM Re: Ch9 table 1 [Re: Tesla]
Rewire Offline
Member

Registered: 02/23/08
Posts: 167
Loc: Missouri


Edited by Rewire (03/17/10 06:27 PM)

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#193076 - 03/18/10 10:44 AM Re: Ch9 table 1 [Re: Rewire]
sabrown Offline
Member

Registered: 12/12/02
Posts: 298
Loc: 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.

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#193122 - 03/19/10 06:32 AM Re: Ch9 table 1 [Re: sabrown]
Rewire Offline
Member

Registered: 02/23/08
Posts: 167
Loc: Missouri
just when it all makes sense they bring in nipples

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