500 kcmil landing

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iaov

iaov

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Location
Rhinelander WI
Getting ready to land four , three conductor 500 kcmil cables in an mcc. It is only a 35 foot run from main to mcc. The boss is concerned that these conductors must be the exact same length (within inches ) or bad things will happen. I don't believe a few inches will make a bit of difference. Anyone have an opinion on this??
 
iwire

iwire

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Location
Massachusetts
iaov said:
Getting ready to land four , three conductor 500 kcmil cables in an mcc. It is only a 35 foot run from main to mcc. The boss is concerned that these conductors must be the exact same length (within inches ) or bad things will happen. I don't believe a few inches will make a bit of difference. Anyone have an opinion on this??
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The code requires the conductors be the same length, the code does not give any tolerance. The shorter the run the more critical it is that the conductors are the same length. The lengths change the impedance and how the current will divide.

That said, a 'few inches' on a 35' run should not cause any other problem then a possible code fail.
 
infinity

infinity

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New Jersey
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Journeyman Electrician
If these are parallel conductors then I agree with your boss. They should be nearly the exact same length. This is a code requirement {310.4} and also a practical requirement to keep the current in each parallel conductor the same.
 
V

Volta

Senior Member
Location
Columbus, Ohio
Assuming no derating, your 4 500s per phase are good for 1520 amps. If your OCPD / load are say 1200 amps, much less of an issue than if you're looking at a 1500 amp load.

Like a full 400 amps on dual 3/0 wires. Any deviation will overload one half of a phase.
 
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