# How many wires in a pipe?

• posted on February 27, 2004, 8:06 pm
I like to do things right and if I don't know something I like to find the answer in writeing but, I can find in writing that over 3 conductors in a conduit must be derated in current capacity. I also have a reference that says you can put, for one example, up to 12 #14 conductors in 1/2" EMT. So in residential single family house wireing, how many #14 and #12 THHN wires can I pull in 1/2" and 3/4" EMT and meet NEC code? Assuming half the wires are hot and half are white neutrals.
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• posted on February 27, 2004, 8:54 pm
John D wrote:

When using different wire sizes, you have to do a calculation. There are also considerations of whether the neutrals are to be counted or not. Complicated question and no single, easy answer.
Do this GOOGLE: http://www.google.com/search?hl=en&ie=ISO-8859-1&q=conduit+fill I got 146,000 hits!
Jim
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• posted on February 27, 2004, 9:08 pm

For simplicity, let's just say all neutrals are counted and all wires are same size. John
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• posted on February 27, 2004, 9:48 pm
John D wrote:

http://www.westernextralite.com/resources/fill.htm (This assumes you're using THHN (or similar) wire)
When applying the ampacity reduction for more than 3 conductors, note that you are allowed to use the 90C ratings in the table for THHN.
Jim
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• posted on February 27, 2004, 9:17 pm
Speedy Jim wrote:

The easiest would be to look up how many #12's you can use and pretend the #14 wires are #12. Otherwise you have to calculate the area of the wires and the area of the conduit and not exceed whatever percentage fill you're allowed.
BTW, as you approach the maximum allowed fill, it gets *very* difficult to maneuver an ELB fitting or inside-corner elbow.
Best regards, Bob
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• posted on February 27, 2004, 10:51 pm
Thank you guys. Good info at that web site. John

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