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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.
 

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

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Derating is overrated

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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