# Is it wrong or right



## JohnJ0906 (Jan 22, 2007)

Well, yes, you are supposed to derate, but not all conductors count towards derating. All conductors *do* count towards fill. 

For instance, 3 "full boats" and a conductor EGC. (3 phase MWBCs)

13 conductors counted towards conduit fill.
9 conductors counted for derating. (EGC and neutrals wouldn't count.)
310.15 (B)(2)(a), (B)(4), and (B)(5)


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## alvarez4563 (Jul 13, 2008)

thanks! johnjo906,alvarez4563


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## brian john (Mar 11, 2007)

Or you are feeding dedicated equipment that might only draw 3 amps each. NO derating necessary. BUT IMO I would avoid max fill just from a feeding standpoint.


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## MikeD (Jul 7, 2008)

i thought the neutrals count towards de-rating....


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## Bkessler (Feb 14, 2007)

If it's a balanced load then then you do not have to count the neutral.


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## randomkiller (Sep 28, 2007)

brian john said:


> Or you are feeding dedicated equipment that might only draw 3 amps each. NO derating necessary. BUT IMO I would avoid max fill just from a feeding standpoint.


 
And that is the best reason. I also tend to go up a size in conduit (or greenfield on control wiring) sometimes for future use, when possible.


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## JohnJ0906 (Jan 22, 2007)

MikeD said:


> i thought the neutrals count towards de-rating....


Yes and no. It depends on whether or no it is carrying the unbalanced current, as in a MWBC, or the full load - a 2 wire circuit. 

If you have (3) 2 wire circuits, hot and grounded each, that would be 6 CCCs. If you pulled that as (1) MWBC, as in (3) hots, (1) grounded [neutral], than you would have 3 CCCs.


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## [email protected] (Jan 19, 2009)

The CEC's max is 11 for number 12awg for 21mm/3/4" EMT and I don't see anything about de-rating


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## cdnelectrician (Mar 14, 2008)

Are you talking T-90 or RW-90?


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## [email protected] (Jan 19, 2009)

R90 600V without jacket yea T90 is good for 16 of number 12awg in 21mm EMT


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## zappy (Mar 6, 2009)

*Derating is overrated*



alvarez4563 said:


> can anyone help me understand why in the code book it says you can put 16 #12awg in a 3/4" emt conduit.I try to keep my wires at 9 for 3/4" and 5 for 1/2".I see alot of guys stuffing 16,15,14 wires in a 3/4" conduit.What ever happen to derating?I personaly dont do it,but when i work with another forman and alot of other guys,i see it all the time. Is it wrong to do this or what?Ive worked with alot of other companiesand if i recall B.C.E. was the only one that derated.


Just kidding.But seriously i see electricians violate this code alot.


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