Reducing Conductors in Parallel

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moonlite

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We have a project where there are 2 parallel sets of 500kcmil aluminum XHHW phase conductors on a circuit with 320A of operating load and a calculated load of 400A for continuous duty. These 500kcmil conductors were selected due to voltage drop. However, terminating these conductors on a 400A frame breaker or heavy duty switch is not simple. The terminals at the breaker are limited to (1) 500 or (2) 250 kcmil. The terminal limits on the disconnect are (1) 750 or (2) 300 kcmil.

Can we use a listed reducing compression splice per phase conductor that would reduce the conductor from 500 to 250 kcmil at the terminal? Then there would be only 4? of 250 kcmil conductor in the circuit. This would basically make a custom sized compression pin adapter. Code references to support your answer is appreciated.
 
moonlite said:
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Can we use a listed reducing compression splice per phase conductor that would reduce the conductor from 500 to 250 kcmil at the terminal? Then there would be only 4? of 250 kcmil conductor in the circuit. This would basically make a custom sized compression pin adapter. Code references to support your answer is appreciated.
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IMO yes... as long as the reducing compression splice is listed for that combination. No code references, as there are none explicitly for this application. Compliance with relevant others is all that matters.
 
Since the parallel 250's will still have an ampacity greater than the OCPD ahead of the feeder then you propose is fine given, as Smart said, that you use the correct listed splicing method.
 
moonlite said:
We have a project where there are 2 parallel sets of 500kcmil aluminum XHHW phase conductors on a circuit with 320A of operating load and a calculated load of 400A for continuous duty. These 500kcmil conductors were selected due to voltage drop. However, terminating these conductors on a 400A frame breaker or heavy duty switch is not simple. The terminals at the breaker are limited to (1) 500 or (2) 250 kcmil. The terminal limits on the disconnect are (1) 750 or (2) 300 kcmil.

Can we use a listed reducing compression splice per phase conductor that would reduce the conductor from 500 to 250 kcmil at the terminal? Then there would be only 4” of 250 kcmil conductor in the circuit. This would basically make a custom sized compression pin adapter. Code references to support your answer is appreciated.
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I don't have a problem with this at all. Seems like the best deal.

You could also splice a 600 to the two 500s and connect that to your DS.

Another possibility is just to replace the lugs on the breaker.
 
petersonra said:
I don't have a problem with this at all. Seems like the best deal.

You could also splice a 600 to the two 500s and connect that to your DS.

Another possibility is just to replace the lugs on the breaker.
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I'm surprised that a 400 amp breaker only allows a 500kcmil conductor as the 75?c rating of a 500kcmil aluminum is only 310 amps? unless the breaker terminals are for copper only? I know we can use the next size up but this surprises me as most breakers will allow one or two sizes up from the rating of the breaker, but if the single 500 is the true limit then the 600 wont help, but a 500 copper could be used using the next size up rule if the calculated load is 400 amps or less.

This breaker and disconnect both seem to disallow aluminum as for 400 amps the smallest aluminum conductor allowed even using the next size up would be an 800kcmil with a rating at 395 amp at 75?c

Not sure about a crimp on that will allow three conductors to be put together as a Polaris type of connection would also work that would accept two 500's to one copper 500 to land in the breaker/disconnect?

To the OP:
Since you are running the parallel conductors for voltage drop keep in mind that the EGC also has to be upsized 250.122(B) so instead of a #1awg aluminum EGC you will need a 3/0 aluminum EGC Of course if this is in metallic conduit then this point is mute.
 
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I often have to get other than the std lugs that breakers come with. as often as not I end up having to order them with non-std lugs. sometimes it is faster or less expensive to order the breaker with standard lugs and replace them over ordering them without lugs or with non-std one.

I ended up with 84 lugs sitting on a shelf that way from a recent job.
 
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