1. Senior Member
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Feb 2004
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Originally Posted by ramsy
Taps are not eligible for next-size up rule. As Kwired notes, 3/0 cu @75c is minimum size for 200A fuse.

35ft inside industrial building, only in industrial occupancies, where conditions of maintenance
and supervision ensure that only qualified persons service the equipment.
Please explain next-size up rule. thanks

2. Originally Posted by hardworker
Please explain next-size up rule. thanks
240.4(B).

3. Senior Member
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Originally Posted by hardworker
Please explain next-size up rule. thanks
NFPA-70 240.21(B)
"..provision of 240.4(B) shal NOT be permitted for tap conductors"

4. Senior Member
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Originally Posted by infinity
You could use #2/0 (minimum size is 400/3=133 amps) you would just need to use 175 amp fuses in the disconnect.
If I go with 175 amp fuses and 2/0 how many feet for the tap?

5. Originally Posted by hardworker
If I go with 175 amp fuses and 2/0 how many feet for the tap?
Same as the aforementioned #3/0.

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Originally Posted by ramsy
Taps are not eligible for next-size up rule. As Kwired notes, 3/0 cu @75c is minimum size for 200A fuse.

35ft inside industrial building, only in industrial occupancies, where conditions of maintenance
and supervision ensure that only qualified persons service the equipment.
Would you give example of the next-size up rule?

7. Say you're installing a 200 amp feeder to a 200 amp panel using #4/0 XHHW with an ampacity of 180 amps. Calculated load on the panel is 150 amps so you can go up to the next standard size OCPD (200 amps, 180 is not a standard size) from 240.6(A) to protect the feeder.

So you have 200 amp panel> 150 amp load> 180 amp conductor> 200 amp OCPD, all code compliant.

8. Originally Posted by hardworker
Would you give example of the next-size up rule?
Say you have a conductor that has an ampacity of 185A. Since 185A is not a standard size breaker or Fuse you are allowed to use the next largest breaker/fuse which would be 200A. However the load would be limited to 185A.

ETA: Sorry Rob, I was posting (slowly) while you were!

9. Senior Member
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Originally Posted by hardworker
Would you give example of the next-size up rule?
I hope you are not attempting this yourself, without a code book, or a clue?

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I am getting old and my memory is not as good as it use to be. I have a young electrician doing most of the work, but I like to check what he is doing. You guys have a lot of knowledge at your fingertips. Many thanks.

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