Pipe sizeing

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nathan1

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I am trying to add a panel using a portion of existing 1 1-4 emt. I want to pull 4 #1 plus a #6 ground. I went to tableC.1 and found that 4 #1 can then to add the ground then did the calc. using Table 5 finding a #1 Thhn is .1562 x 4=.6248. Then going back to Table 4 article 358 I find the over 2 wires 40% cat. is only .598!!! Which contradicts table c.1!!! I must be missing something any help would be app. thanks in advance!!
 
Re: Pipe sizeing

This happens quite often for many different calculations. Annex C always seems to allow a slightly higher fill verses the Table 4 and 5 method. Considering you are installing more than one size conductor in the same raceway, you cannot use Annex C anyway. So just go off the Table 4 and 5 calculation. See note 1 to Chapter 9 Tables.
 
Re: Pipe sizeing

Look at Notes to table 1 Chapter 9 , note # 1. Its says if conductors are the same size you can use Table C1. If conductors are different, you must calculate using Note #6
 
Re: Pipe sizeing

I appreciate the help thanks!!! Can anyone double check my calc. that 1 1-4 will NOT work for 4 #1 thhn plus one #6 thhn for ground. There is someone at my shop that is saying it is possible. Thanks again.
 
Re: Pipe sizeing

Can you use the 1 1/4" emt in place of the #6?
As I understand your post, the #1's would fit; it is the #6 that is putting you over.
 
Re: Pipe sizeing

That is a possibility I will bring up to my boss. Right now I want to make sure my calculations are right. C.1 states that 4 #1 thhn cond.can fit in 1 1-4 emt. Where as Chap.9 table 4 states that a #1 thhn cond. has an area of .1562x4=.6248 the area of a 1 1-4 emt at 40% for more than two cond. is only .598. This tells me with my calc. out of table 4 is saying the I can only put in 3 conductors. This is contradicting the table C.1. My fear is that I am doing my calculations wrong but I can seem to find out where. I was hoping someone could verify my findings before I present them to my boss. Thanks for all the responses so far.
 
Re: Pipe sizeing

Evidently you are using your #1s for a 100 Amp load. In developing my super chart, I noticed an anomoly. If you use a 110 amp breaker, it will be rated for 75? so you can use #2 cables. however a 100 amp breaker is rated for only 60? conductors -- thus forcing you to use #1s.
~Peter
 
Re: Pipe sizeing

peter,
however a 100 amp breaker is rated for only 60? conductors -- thus forcing you to use #1s.
Click to expand...
Most all of the breakers on the market now are rated for 75?C conductors.
Don
 
Re: Pipe sizeing

Dang! Why did they have to go and do that? I am using the California 1999 Code and there is something in there that said breakers 100 amps and under were rated at 60?.
Don't these manufacturers realize that by increasing the temperature limits, they are sabotaging my great chart?
In any case, if the breaker is now rated at 75? and the original poster is supplying a 100 amp panel, then why can'the use #2 wires?
~Peter
 
Re: Pipe sizeing

Peter,
Dang! Why did they have to go and do that? I am using the California 1999 Code and there is something in there that said breakers 100 amps and under were rated at 60?.
Click to expand...
The code wording is still the same in the 2005 code, but the listing and marking of the breakers is not.
Don
 
Re: Pipe sizeing

Originally posted by don_resqcapt19:
Peter,
Dang! Why did they have to go and do that? I am using the California 1999 Code and there is something in there that said breakers 100 amps and under were rated at 60?.
Click to expand...
The code wording is still the same in the 2005 code, but the listing and marking of the breakers is not.
Don
Click to expand...
As stated most CB's are listed for 75 degrees. Using the 75 degree conductor rating would be permitted according to #3 from 110.14(C)(1)(a)(3):

(1) Equipment Provisions. The determination of termination provisions of equipment shall be based on 110.14(C)(1)(a) or (C)(1)(b). Unless the equipment is listed and marked otherwise, conductor ampacities used in determining equipment termination provisions shall be based on Table 310.16 as appropriately modified by 310.15(B)(6).
(a) Termination provisions of equipment for circuits rated 100 amperes or less, or marked for 14 AWG through 1 AWG conductors, shall be used only for one of the following:
(1) Conductors rated 60?C (140?F).
(2) Conductors with higher temperature ratings, provided the ampacity of such conductors is determined based on the 60?C (140?F) ampacity of the conductor size used.
(3) Conductors with higher temperature ratings if the equipment is listed and identified for use with such conductors.
(4) For motors marked with design letters B, C, or D, conductors having an insulation rating of 75?C (167?F) or higher shall be permitted to be used, provided the ampacity of such conductors does not exceed the 75?C (167?F) ampacity.
Click to expand...
 
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