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Old 10-19-2012, 10:15 PM   #1
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Default Welding cable for Genset Power

I worked for a guy today, who was running 12 sets of Welding Cable paralleled to get 1200A from a Generator to the ATS.

The cable seemed small to me to get 300A + out of , but it read 4/0. I'm Trying to figure out in the NEC 310.15 where is the rating for that wire ? You would need to get about 300A minimum plus extra size for VD. What column would you use, and what kind of cable are Generator rental places providing ?

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Old 10-19-2012, 10:21 PM   #2
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Was it single conductors? I believe what you have is called Exane...It is used widely in the locomotive industry and the free air rating is higher than regular wire..

http://www.electrowire.com/spec-sheet-test-2/

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Old 10-19-2012, 10:28 PM   #3
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You can only use welding cable or DLO cable in NEC applications if it dual rated RHH-RHW.
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Old 10-19-2012, 11:05 PM   #4
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@ Glen, yeah I looked that stuff up online. I don't know how many conductors, I'll check it out if I work again with this guy. Looked like SO cord.

JLarsen, So look for dual rated, You would think the rental yards would have to supply the right stuff.
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Old 10-19-2012, 11:11 PM   #5
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Quote:
Originally Posted by dronai
I worked for a guy today, who was running 12 sets of Welding Cable paralleled to get 1200A from a Generator to the ATS.

The cable seemed small to me to get 300A + out of , but it read 4/0. I'm Trying to figure out in the NEC 310.15 where is the rating for that wire ? You would need to get about 300A minimum plus extra size for VD. What column would you use, and what kind of cable are Generator rental places providing ?
I believe the proper cable is s.c. or type w. We use stage cable which I think is s.c. but we did and still sometimes use 600 volt rated welding cable, I know Sunbelt rents it and im sure Hawthorne power does as well , the amperage ratings are a bit diff as well
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Old 10-19-2012, 11:51 PM   #6
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Just FWIW, Stage Cable is considered a portable cable (Article 400) so you can't use it in conduit, say to like a big motor to make termination easy like you could dual rated DLO.
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Old 10-20-2012, 12:29 AM   #7
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Just FWIW, Stage Cable is considered a portable cable (Article 400) so you can't use it in conduit, say to like a big motor to make termination easy like you could dual rated DLO.
True true I assumed since he was talk tying a portable gen into a transfer switch he was not using a raceway
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Old 10-20-2012, 09:15 AM   #8
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4/0 gen cables are rate 400a each! Spend alot of time working temp pwr feeds....
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Old 10-20-2012, 09:19 AM   #9
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4/0 gen cables are rate 400a each! Spend alot of time working temp pwr feeds....
Yes and no.

They are rated by the manufacturer for 400 amps, they are not rated 400 amps by the NEC.

That said, when we use them (and we do a lot of this) we consider them 400 amp, but let me explain.

If we had to supply a 2000 amp main, we would run five sets, but the actual load will be well under 2000 amps. So we don't really run the cables at 400 amps of load each.
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Old 10-20-2012, 09:27 AM   #10
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Yes and no.

They are rated by the manufacturer for 400 amps, they are not rated 400 amps by the NEC.

That said, when we use them (and we do a lot of this) we consider them 400 amp, but let me explain.

If we had to supply a 2000 amp main, we would run five sets, but the actual load will be well under 2000 amps. So we don't really run the cables at 400 amps of load each.
WHAT BOB SAID.

Though we do testing on a job where the load bank vendor assumed this and they installed 2000 amp worth of cable (5 sets)and the engineers doing the commissioning put 2000 amps on it. The cable was sticky to the touch after the test the cable cooled down but was stiffer than pre-test.

We lost the load bank portion of the job as we calculated the cable at 7 sets.
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Old 10-20-2012, 09:35 AM   #11
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The cable was sticky to the touch after the test the cable cooled down but was stiffer than pre-test.
A large EC was doing high voltage distribution work and had screwed up killing power to an entire mall and one of our customers supermarkets. It was up to this contractor to supply a genset and temp feed the supermarket at 480 volt. before they lost product.

Our customer requested two of us to observe the work being done to make sure their equipment was not damaged. We told the EC they needed to run three sets o cables to do it. They looked at us like we were stupid and set it up with two sets. within a very few minutes the cables where more than warm so they had to shut down and add the third set.

I can't miss the opportunity to point out this other contractors crew were highly trained members of IBEW 99. They were so happy to be watched over by merit shop workers.
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Old 10-20-2012, 09:48 AM   #12
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We know that NEC is very conservative, so I'm really surprised that pushing the cables beyond the NEC limit to design rating by the manufacturer screws up the insulation.

Seems kinda hard to claim it will pass that current if passing that current would eventually cause it to fail.

-John
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Old 10-20-2012, 10:36 AM   #13
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Quote:
Originally Posted by BBQ

Yes and no.

They are rated by the manufacturer for 400 amps, they are not rated 400 amps by the NEC.

That said, when we use them (and we do a lot of this) we consider them 400 amp, but let me explain.

If we had to supply a 2000 amp main, we would run five sets, but the actual load will be well under 2000 amps. So we don't really run the cables at 400 amps of load each.
I agree with what u said and do the same!
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Old 10-20-2012, 11:03 AM   #14
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Don't tell anyone but I have been in a bind before and stuffed thhn in greenfield and left it sitting on the ground to get tied in before,
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Old 10-20-2012, 11:06 AM   #15
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We know that NEC is very conservative, so I'm really surprised that pushing the cables beyond the NEC limit to design rating by the manufacturer screws up the insulation.

Seems kinda hard to claim it will pass that current if passing that current would eventually cause it to fail.

-John
400 amps on 4/0 especially if they are laying on top of each other, oh yeah
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Old 10-20-2012, 12:09 PM   #16
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I'm not surprised they get hot I'm just surprised the insulation starts to fail.

-John
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Old 10-20-2012, 12:33 PM   #17
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Originally Posted by Big John
I'm not surprised they get hot I'm just surprised the insulation starts to fail.

-John
Once a conductor is heated beyond the temperature rating of its insulation , the insulation will start to break down . Especially if these cables are always being overloaded . Once that temperature rating is exceeded the breakdown process starts . It may take a good long while before they start shorting out and become unusable, but it will happen eventually .
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Old 10-20-2012, 12:34 PM   #18
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Esp cuz tye insulation 1st layer is a silicone insulation (usually white) followed by a black rubber layer.
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Old 10-20-2012, 12:54 PM   #19
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Once a conductor is heated beyond the temperature rating of its insulation , the insulation will start to break down . Especially if these cables are always being overloaded....
Without seeing the cutsheets for these cables it doesn't sound like they were being overloaded, that's what I'm getting at.

Now how much of the heat was due to bundling or ambient, I have no idea, but if I a manufacturer sells me cable and claims a cable is designed for 400A I would not expect 400A to cause the insulation to get gluey.

-John
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Old 10-20-2012, 12:59 PM   #20
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Quote:
Originally Posted by Big John
Without seeing the cutsheets for these cables it doesn't sound like they were being overloaded, that's what I'm getting at.

Now how much of the heat was due to bundling or ambient, I have no idea, but if I a manufacturer sells me cable and claims a cable is designed for 400A I would not expect 400A to cause the insulation to get gluey.

-John
No , I agree with you , but without seeing cable specs it's all speculation . Bundling with Ty wraps sure wont help this situation , lol !

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