wsamuelson
New member
- Location
- Colorado
My boss has asked me if I can put 4-#12 and 3-#10 THHN in 1/2" EMT. My response was NO, I need some confirmation.
Thanks, Willie Samuelson
Thanks, Willie Samuelson
number of cond. in 1/2" EMT
- Thread starter wsamuelson
- Start date
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lectrishun
Member
- Location
- Missouri
Re: number of cond. in 1/2" EMT
See NEC Chapter 9.
See NEC Chapter 9.
- Location
- Lockport, IL
- Occupation
- Retired Electrical Engineer
Re: number of cond. in 1/2" EMT
I think you can do as your boss has requested. From Chapter 9, Table 4, a 1/2 inch EMT has an available area (at 40% fill) of 0.122 square inches. From Table 8, a #12 has an overall area of 0.006 square inches, and a #10 has an overall area of 0.011 square inches. Therefore, 4 #12 and 3 #10 would have a total area of 0.057 square inches. This is less than the 40% fill number (.057 < .122), and is therefore acceptable. I don?t believe that this type of ?calculation? would require ?engineering supervision.?
I think you can do as your boss has requested. From Chapter 9, Table 4, a 1/2 inch EMT has an available area (at 40% fill) of 0.122 square inches. From Table 8, a #12 has an overall area of 0.006 square inches, and a #10 has an overall area of 0.011 square inches. Therefore, 4 #12 and 3 #10 would have a total area of 0.057 square inches. This is less than the 40% fill number (.057 < .122), and is therefore acceptable. I don?t believe that this type of ?calculation? would require ?engineering supervision.?
- Location
- Lockport, IL
- Occupation
- Retired Electrical Engineer
Re: number of cond. in 1/2" EMT
Let me add two observations.
First, Table C1 says you can pull 5 #10 THHN into a 1/2 inch EMT. It is clear that if you pull only 3 #10, there will be ?some room? left. But is it enough room to pull 4 #12? You cannot get that type of information from a single table. You have to go through the process shown above.
Secondly, if you do pull the conductors as your boss has requested, you will have to de-rate per Table 310.15(B)(2)(a) to 70%, presuming that all 7 conductors are ?current-carrying.?
Let me add two observations.
First, Table C1 says you can pull 5 #10 THHN into a 1/2 inch EMT. It is clear that if you pull only 3 #10, there will be ?some room? left. But is it enough room to pull 4 #12? You cannot get that type of information from a single table. You have to go through the process shown above.
Secondly, if you do pull the conductors as your boss has requested, you will have to de-rate per Table 310.15(B)(2)(a) to 70%, presuming that all 7 conductors are ?current-carrying.?
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