Conductor Derating Question

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Eurbin Electric

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Lancaster, CA Los Angeles county
When installing more than 3 current carrying THHN conductors in a conduit they must be de-rated. Can you use the ampacity from the 90 degree column of table 310.16 as a starting point for the calculation if the breaker you are landing on has a termination value of only 75 degrees?
 
Eurbin Electric said:
When installing more than 3 current carrying THHN conductors in a conduit they must be de-rated. Can you use the ampacity from the 90 degree column of table 310.16 as a starting point for the calculation if the breaker you are landing on has a termination value of only 75 degrees?
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Just out of curiosity, why would you want to use insulation rated @ 90 degrees as opposed to 75 degrees IF the reason is other than shortage of material on hand?
 
No, I haven't heard of it....Enlighten me.


Looking at the question now I understand.....I was tied up around the breaker termination being rated for 75 degrees.....
 
The phrase "full boat" is a common "trade slang," and is specifically intended to apply to a multi-wire branch. It refers to a set of five wires: Phases A, B, and C, the neutral, and the equipment ground (although if you use the conduit to serve as an EGC, you don't need the fifth wire). If you look at all the relevant NEC articles (I think that three come into play here), you will see that you can put three "full boats" into the same conduit, if you use THHN or another conductor type that is rated for 90C, and still use #12 wire and 20 amp 3-pole circuit breakers. If you try to put four full boats into the same conduit, and want to use 20 amp breakers, you need to upsize to at least #10 wire.
 
John120/240 said:
Full Boat, Full House, Round House... I'm sure there are other acroymons for a full boat
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Hmm... not acronyms... just slang [trade] terminology.

One electrician I used to work with used the terms "edisons". A three-wire or partial edison would be two hots and a neutral (usually w/grd) on a wye system.
 
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