We designed one set of 750KCMIl feeder cable for a compressor. But the starter for the compressor has two sets of 3/0-500KCMIL lugs. And the set of 750KCMIL cable has been installed. Do you guys know what is the cheapest way to make the transition from 750KCMIL cable to two sets of 300KCMIL cables? Thanks.
one 750KCMIL cable to two smaller calbes
- Thread starter dahualin
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Cold Fusion
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But the right lugs for the starter? Mfgf should show them, if available.
cf
cf
kingpb
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ILSCO Brand; CPM-750 700 kcmil, 750 kcmil
It's a compression connector with a 500KCMIL pin on the end, so it will go into the lug.
It's a compression connector with a 500KCMIL pin on the end, so it will go into the lug.
Great if the wire is oversized for voltage drop. But are you sure the lug cna handle the current that the 750KCM might be sized for?
kingpb
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How many amps you need? 750KCMIL is good for 475A @ 75 deg C. but you were going to use 2 x 300KCMIL which is 570A @ 75 deg C.
Is the cable (750 KCMIL) oversized for voltage drop?
Need more specifics.
kingpb
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They are rated for the full ampacity of the incoming conductor. That's the beauty of them.
Cold Fusion
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kingpb
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Why would you go to that expense instead of using the Ilsco pins as suggested?
But what about the lug on the compressor?
kingpb
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Well it's just a guess, but I would imagine the lugs on the compressor are rated for the full load current of the compressor,:roll:,
Typically, 750KCMIL isn't used very much, due to it's difficult to work with, and 3/0-500KCMIL is pretty standard size lug.
3/0 is good for 200A, parallel would be 400A, a single 500KCMIL is good for 380A. So, suffice it to say that the compressor is probably needing no more than 380A, probably less. The fact 750KCMIL was used, if not for voltage drop, doesn't really matter, it isn't going to carry more than 400A.
I checked their website. Are they talking about the incoming AL conductor? If the incoming conductor is copper, how can 500KCMIL pin is rated for 750KCMIL copper cable?
kingpb
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They are dual rated for copper or aluminum. I'm just going by what they have listed, if you have further questions you need to call the ILSCO rep., but probably due to the fact it's compressed and compact lay design.
Yes, that does seem odd at first. But after you think about it, there are a lot of differences between a wire and a termination pin. Kingpb mentioned a few, and I can think of a few more - like they can have different temp. limits.
And I agree with kingpb that the lug ratings probably wouldn't be a problem. But I would suggest calling the starter manufacturer just to get their take on it before using the reducing pins. Hopefully, they would tell you no problem.
Steve
LarryFine
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And lengths.
kingpin,
You can't say that the compressor won't need more than 380amps, the starter has dual
lugs and could take 2 500KCMIL conductors for 760amps, the question is will one lug with
a crimp type connector be overloaded at 475amps, the rating of the 750KCMIL ?
kingpb
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Valid point, except the designer only ran one set of 750KCMIL, so the total FLA of the compressor can't be more than 380A (475 x .8) = 380A, assuming the 750KCMIL were sized properly.
Just shootin from the hip with very little info.
Yes, that has to be the most obvious difference :grin:
I was also thinking that lugs aren't bundled with 3 inside a conduit. When they determined the ampacity rating of different conductors, they obviously had to take into account the mutual heating inside a conduit.
I assumed that if the wire has to be sized for 125% of the FLA, the terminations had to have the same capacity.
Edit: I can't cite a code reference: It just never occured to me the lugs might be allowed to be less than the conductor ampacity.
Steve
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