emt conduit installation

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sunshine

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the installation of 40 feet EMT conduit with 3 each -2 AWG THHN, 4 each-6 AWG THHN and 3 each -10AWG THHN conductors . what is the minimum conduit size. Thanks Bill
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Re: emt conduit installation

Bill, just for fun, go to chapter 9 and try to figure it yourself.

Might this be an exam question? :)

Roger
 
Re: emt conduit installation

Bill, after rereading my reply, it doesn't come across the way I meant it. :(

Do the calculations and post your conclusion here for a verification or correction.

Roger

[ January 21, 2005, 10:41 PM: Message edited by: roger ]
 
Re: emt conduit installation

I hope I don?t step on any toes. I thought I would give a stab at this. It has been a while since I have done this. This is for my own edification.

Table 5, Chapter 9

3-- # 2 THHN @ .1158 = .3474 in2
4-- # 6 THHN @ .0507 = .2028 in2
3-- # 10 THHN @ .0211 = .0633 in2

I come up with .6135 in2

Table 4, Chapter 9
Over 2 @ 40% -- 1 1/2 EMT @ .814 in2

I would like to take this one step further, what about ?derating? (adjustment factor, Table 310.15(B)(2)(a)) for this situation? I would think without knowing the # of Current Carrying Conductors we could not get a good answer. Is this correct?

Norb
 
Re: emt conduit installation

Originally posted by 1793:
I would think without knowing the # of Current Carrying Conductors we could not get a good answer. Is this correct?

Norb
Click to expand...
yes, but why would anyone run conductors that big if they carried no current?
 
Re: emt conduit installation

Originally posted by petersonra:
yes, but why would anyone run conductors that big if they carried no current?
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Bob many times the NEC does not count the neutral as a current carrying conductor for the purposes of derating.

We do not know from the opening post if all the conductors are current carrying or not.

Check out 310.15(B)(4)(a),(b) & (c).
 
Re: emt conduit installation

I guess if I looked closer and figured on only one of the # 10's was a neutral, not counted per 310.15(B)(4)(a), we would use a count of 7-9 @ 70%. What might I be missing?

Norb

[ January 23, 2005, 10:01 AM: Message edited by: 1793 ]
 
Re: emt conduit installation

Norb, you are correct, and as far as an exam, the question couldn't be answered for derating of conductors, only conduit fill.

Roger
 
Re: emt conduit installation

to the conduit fill question 3#2thhn ,4#6thhn and3#10thhn copper conductors,supplied from a braker having 75degree C,termination #6 thhn=0.0507x3=0.1521 . #2thhn=0.01158x2=0.2316 #10thhn=0.0211x3=0.0633 The total=0.447sqinch table 4 chapter 9 EMT conduit at40% fill=0.447=0.598sq inch Table 4 shows 1.25 EMT CONDUIT. Did i miss anything? thanks Bill
 
Re: emt conduit installation

You only counted (2) #2's. Why not (3)??

If this is a test question, and that was the only given info, I would count All of them for the answer.
 
Re: emt conduit installation

to the question of the conduit fill:3#6 thhn=0.2028, 3#2thhn=0.3474. and 3#10thhn=0.0633.the total of 0.6135 with 40%fill table 4 EMT conduit =1.5 size,is this correct? thanks Bill
 
Re: emt conduit installation

For THHN insulated wire (3)#10 , (4)#6, (3)#2 in EMT conduit I would recommend using 1-1/2" size.

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David ;)
 
Re: emt conduit installation

Originally posted by sunshine:
to the question of the conduit fill:3#6 thhn=0.2028, 3#2thhn=0.3474. and 3#10thhn=0.0633.the total of 0.6135 with 40%fill table 4 EMT conduit =1.5 size,is this correct? thanks Bill
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Bill, you are correct for the tubing size, but you need to look at the #6 again. .

Roger

[ January 24, 2005, 02:38 PM: Message edited by: roger ]
 
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