Is it 500 kcmils or 600 kcmills with 400 amp OCPD?

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cppoly

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Is the only difference that 500 kcmils allows you to go up to a 380 amp load and 600 kcmils gives you that extra 20 amps from 380 – 400 amps if you happen to be in that range?
 
Yes that's about it. Depending on length less voltage drop with the 600's. If you're feeding a 400 amp panel/OCPD from a transformer then you must use the 600's as the next size up rule is not permitted for 500's.
 
500 kcmils are good for 380
600 kcmils are good for 420

I agree with transformer secondary conductors since next size up isn't allowed.

But for a feeder on a 400 amp OCPD, if the load falls in between 381 and 400 amps, then are 600 kcmils required? And if the load is under 381 amps then 500 kcmils are good.
 
I haven't used a lot of 600mcm.

Most times at those amperages we are paralleling, but, I was told that the stranding on 600 mcm actually makes it easier to work with than 500mcm.


Is that true?


JAP>
 
cppoly said:
But for a feeder on a 400 amp OCPD, if the load falls in between 381 and 400 amps, then are 600 kcmils required? And if the load is under 381 amps then 500 kcmils are good.
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I agree with this statement.

 
jap said:
I haven't used a lot of 600mcm.

Most times at those amperages we are paralleling, but, I was told that the stranding on 600 mcm actually makes it easier to work with than 500mcm.


Is that true?


JAP>
Click to expand...

No!
 
infinity said:
Yes that's about it. Depending on length less voltage drop with the 600's. If you're feeding a 400 amp panel/OCPD from a transformer then you must use the 600's as the next size up rule is not permitted for 500's.
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More specifically, a customer-owned transformer. If the utility owns the transformer the conductors would classify as service conductors instead of transformer secondary conductors where 240.21(C) applies.

500 kcmil Cu is 380A, which "rounds up" to 400A, and qualifies as "protected" per 240.4(B). You can take credit for this as long as the calculated load does not exceed 380A, and as long as it is a circuit where 240.4(B) is allowed to apply. Feeders, branch circuits, service conductors.

600 kcmil Cu is what you'd need for 400A, if calculated load is between 380A and 400A. Or if 240.4(B) cannot be applied. Such as when 240.21(B) or (C) applies instead.

Note that when you scale it up beyond 800A, such as 1200A, it is no longer 3 sets of 500 kcmil. You now need as much amps of conductors as you have of OCPD, in all applications.
 
sameguy said:
Hell No!
It is almost like 100mcm bigger! and bends like it too. Put your big boy pants on and have fun keeping stress off the breaker.
Do you have experience bending large wire?
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Almost ????? :)


JAP>
 
sameguy said:
Hell No!
It is almost like 100mcm bigger! and bends like it too. Put your big boy pants on and have fun keeping stress off the breaker.
Do you have experience bending large wire?
Click to expand...

Yes, plenty. We routinely use up to 750 kcmil copper. I generally avoid the 750's like the plague, we have some younger guys to wrestle with that stuff. I do frequently work with 600's. Recently I had to deal with this disaster, 600 kcmil copper in an installation that they call "field conditions". Oh forgot to mention that the wire was pulled before the wireway was installed. :slaphead:
.

20190507_110528.jpg
 
infinity said:
Yes, plenty. We routinely use up to 750 kcmil copper. I generally avoid the 750's like the plague, we have some younger guys to wrestle with that stuff. I do frequently work with 600's. Recently I had to deal with this disaster, 600 kcmil copper in an installation that they call "field conditions". Oh forgot to mention that the wire was pulled before the wireway was installed. :slaphead:
.

View attachment 23272
Click to expand...



I see some of those bondless bonding bushings being used.


JAP>
 
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jap said:
I haven't used a lot of 600mcm.

Most times at those amperages we are paralleling, but, I was told that the stranding on 600 mcm actually makes it easier to work with than 500mcm.


Is that true?


JAP>
Click to expand...
If they increase the number of strands, maybe. Still large enough that it bends hard.

I know that jumping from 4/0 aluminum to 250 aluminum number of strands increases and that 250 can be easier to bend than 4/0. But that is not as big a jump in CSA as 500 to 600 either.
 
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