Parallel Conductor sizing.

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SurfSide EC

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I could use some help parallel sizing a 600 3-phase amp service. I have only done a couple of services over 400 amp and that was several years ago. My biggest question is how to size the parallel into 3 conductors as opposed to 2 if I decide to go that route (which I never have, but it seems I read about it here somewhere.) I am checking now but figured I would post in case I run into questions, which is highly likely :rolleyes: . Thanks for the help.
 
OK, I'll take a stab at this of course at the scrutiny of my fellow cyber comrades.
I'm assuming CU conductors and a linear load situation where harmonics are not a factor therefore not requiring the neutral to count as a CCC. Also assuming a 30 degree C ambient not requiring any derating for temp.

I'd say you could run 3 sets of 4/0's with an OCPD of 600A with each group of service entrance conductors in separate conduits.
 
Yes, you are right with the specs I left out. I do those details standard so much I forget to include the details. It drives the supply house guys crazy sometimes, too. Sorry.

Thanks for the info. Is there a formula for this (I'm sure here is, duh)? I've gotten a little to attatched to the online calculators. It's kinda like speed dial on the cell phone. I know about 5% of my phone numbers and everything else is #28, etc. :grin:

Edit: We are adding a 600amp 3-phase 480volt MTS and plug for a portable generator to an existing service at a bank. The switch is mounting right next to meter cabinet.
 
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110.3(B) & 110.14(A) - the last sentence.

Paralleling with 2 sets of conductors may not be an issue, but 3 sets for this size overcurrent device may be an issue. There are generally 2 sets of lugs or 1 set of lugs listed for 2 conductors.
Having 3 sets of lugs is a different story and may require some adjustment to the enclosure/existing lugs, that will be field adjustment. Therefore it may need a field inspection or at least approval (in writing) from the manufacturer.
 
Personally I would use two sets of 350 Cu conductors. If your connected load is 570 amps or less you can get away with two sets of 300's. And if you can use a nipple less than 24" you can get away with only one raceway.
 
infinity said:
And if you can use a nipple less than 24" you can get away with only one raceway.
Click to expand...

Interesting....I always thought that paralleled conductors had to always be separated ABCN/ABCN. Didn't know about the 24" rule. Is there a reference?
 
m73214 said:
Interesting....I always thought that paralleled conductors had to always be separated ABCN/ABCN. Didn't know about the 24" rule. Is there a reference?
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I was saying that you can put them all in one raceway if the raceway is 24" or less. By doing that, derating wouldn't apply. 310.15(B)(2) Ex 3.
 
m73214 said:
Got it Trevor. I was typing before I was thinking again......
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No problem. He said that the two pieces of equipment were right next to each other so maybe a single raceway 24" or less will work.
 
Pierre C Belarge said:
110.3(B) & 110.14(A) - the last sentence.

Paralleling with 2 sets of conductors may not be an issue, but 3 sets for this size overcurrent device may be an issue. There are generally 2 sets of lugs or 1 set of lugs listed for 2 conductors.
Having 3 sets of lugs is a different story and may require some adjustment to the enclosure/existing lugs, that will be field adjustment. Therefore it may need a field inspection or at least approval (in writing) from the manufacturer.
Click to expand...

I can vouch for this. Just had a project where I had specced 3 sets of 300's from a 600A breaker. Got informed by the electrician that the breaker only had 2 conductor lugs. Ended up with 2 sets of 500. Feeder is to a 800A Main in an MCC that may be added to.
 
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