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Old 01-24-2015, 03:07 PM   #1
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Default Parallel feeders

Can I have some one help me be a little less ignorant? I need to use 4 750kcmil copper conductors to run 225 amps 1000' to a 480v panel 3 phase 4 wire. I want to reduce the cost by using smaller wires in parallel. What formula can I use to calc the wire size. Or does anyone know this off of the top of their head?
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Old 01-24-2015, 03:41 PM   #2
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Chapter 9 table 8 in 2011 nec.
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Old 01-24-2015, 03:50 PM   #3
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Using parallel conductors to reduce voltage drop does not reduce the amount of copper you need. If the voltage drop calc shows you need 750kcmil, then you will need parallel conductors that total at least 750 kcmil, for example three sets of 250 kcmil.
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Old 01-24-2015, 04:00 PM   #4
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That is a good point what Don stated. You don't use the ampacity chart to calculate the parallel size in this case because we are dealing with voltage drop.

If, for instance, you needed a conductor that carried 475 amps as 750 kcm does then if amp. was all we were looking for then we could use parallel 250 kcm (2 sets not 3) but because of the voltage drop the cm must be equal so as Don stated 3 sets of 250 KCM would equal the 750 KCM
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Old 01-24-2015, 04:36 PM   #5
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VD calculator


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Old 01-24-2015, 09:25 PM   #6
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That will be a fortune, all our long runs like that are done in aluminum.
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Old 01-25-2015, 12:57 AM   #7
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That will be a fortune, all our long runs like that are done in aluminum.
I couldn't agree more. Heck, I use aluminum for anything over 50'. I couldn't imagine using copper for a 1000' feeder.
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Old 01-25-2015, 07:28 AM   #8
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Iirc, there's an engineered pull pressure one should not exceed, or damage may occur


I would imagine the weight of it alone would require multiple pull points, lest it defeat a tugger.


Weight is probably the best reason to parallel...


just my wimp opinion

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Old 01-25-2015, 09:27 AM   #9
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I couldn't agree more. Heck, I use aluminum for anything over 50'. I couldn't imagine using copper for a 1000' feeder.
We did 3 runs of 3C500 5kv teck on a job that was 285 meters (935').. I think for the one half we had 16 guys on it... There was 2 runs on one reel and when we pulled the first one in, it was 7 meters short... Fortunately it was a quick fix and became long enough, but we had quite a bit of excess on the second one...

We had another one on that site that was a 4C2/0 that was close to 500 meters (1,640') if I remember right.. It was feeding a light and a heat trace circuit on a well...
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Old 01-25-2015, 09:40 AM   #10
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We did 3 runs of 3C500 5kv teck on a job that was 285 meters (935').. I think for the one half we had 16 guys on it... There was 2 runs on one reel and when we pulled the first one in, it was 7 meters short... Fortunately it was a quick fix and became long enough, but we had quite a bit of excess on the second one...

We had another one on that site that was a 4C2/0 that was close to 500 meters (1,640') if I remember right.. It was feeding a light and a heat trace circuit on a well...


Quick fix ??
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Old 01-25-2015, 10:15 AM   #11
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16 man stretcher?



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Old 01-25-2015, 10:45 AM   #12
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I would offer the owner a big deduct to use Alum.....then pocket half the savings
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Old 01-25-2015, 10:59 AM   #13
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I would step the voltage up on the feed end and reduce it down on the other end. Two small transformers will save you alot of copper.

Last edited by mcclary's electrical; 01-25-2015 at 12:06 PM.
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Old 01-25-2015, 11:23 AM   #14
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Quick fix ??
The cables came from the west and went along the full width of the north side of the building, then went south for about 30' then turned back to the west and inside for about 20'... We added two lengths of tray from the north wall straight inside above the gear and cut our distance down by quite a bit.. Sold it to the engineers on cable tray loading and got the fix ok'd... The boss wasn't ok initially with the scrap tails, but after he heard the reason why, or fix for it and that otherwise we'd have had a 275 meter scrap piece, he was ok with it..
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Old 01-25-2015, 11:32 AM   #15
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I would step the voltage up on the feed on and reduce it down on the other end. Two small transformers will save you alot of copper.
It was a 4,160 volt feeder off the generator to a 4,160 volt distribution panel in another MCC building. Adding 4 transformers wasn't an option, mainly for real estate at each building, and I'm guessing the cost would have been close...
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Old 01-25-2015, 12:02 PM   #16
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It was a 4,160 volt feeder off the generator to a 4,160 volt distribution panel in another MCC building. Adding 4 transformers wasn't an option, mainly for real estate at each building, and I'm guessing the cost would have been close...
He's talking to the OP
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Old 01-25-2015, 12:28 PM   #17
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I would step the voltage up on the feed end and reduce it down on the other end. Two small transformers will save you alot of copper.
I don't see the advantage of bumping a 480v feeder to what, 600v? That isn't much gain. Installing transformers that burn Kw's all day long as well as extra disconnects/OCPD's make this less than ideal in the long run.

I'd pull aluminum and be done with it.
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Old 01-25-2015, 02:40 PM   #18
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Quote:
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I don't see the advantage of bumping a 480v feeder to what, 600v? That isn't much gain. Installing transformers that burn Kw's all day long as well as extra disconnects/OCPD's make this less than ideal in the long run.

I'd pull aluminum and be done with it.
Not to mention the additional terminations and installation time of 2 more transformers...
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Old 01-25-2015, 07:30 PM   #19
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Quote:
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I would step the voltage up on the feed end and reduce it down on the other end. Two small transformers will save you alot of copper.
Agree.
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Old 01-25-2015, 07:56 PM   #20
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Quote:
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Not to mention the additional terminations and installation time of 2 more transformers...
Aluminum is worse for v.d. Plan on running twice the conduit, and pull twice the runs.
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