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Thread: Getting #250 Al onto 1/0 Lugs

  1. #1
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    Getting #250 Al onto 1/0 Lugs

    We have a large multi-family mixed use building we are just now bringing out of the ground. We're trying to figure out a solution to the over-sized conductors on too-small lugs. All of our residential units require only a 100Amp loadcenter. We've solved the connection at that end of the feeder by buying 150A rated MLO loadcenters which have lugs good for up to 300KcMIL. However, it's the other end that has me concerned. The meter/main meter packs we're using are Eaton (Cutler-Hammer) and the 2-pole mains will be BR2100 circuit breakers. Submittal sheets say the maximum wire size on their lugs is 1/0. However, due to distances, we have about half the building requiring #2/0 feeders, plus a small handful of them at both #4/0 and #250KcMIL. I've been researching ways to reduce the conductor size to fit on the 1/0 lugs but not finding anything conclusive. Am curious to know what others have done as inevitably, there are others who have run into this before us. I can't find any manufacturers who make a compression reducer that will go from 250 to 1/0. Mechanical lugs are plentiful for this. I'm hoping I can find out from others what they've done in the past. Also curious about code quotation to back us up with the inspector for having 10' of 1/0 AL at the beginning of a #250 AL feeder in case they have a problem with it.

  2. #2
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    There is no code quotation to back up your plan because the code is permissive. It does not list exhaustively all the things that are allowed.

    You are using larger conductors to limit voltage drop. Do the voltage drop calculation adding 10' of smaller, but code approved, wire at the end and notice that the difference is negligible.
    Doing what you suggest is a separate junction box will also avoid any bending space problems with the larger wire.

  3. #3
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    Quote Originally Posted by GoldDigger View Post
    There is no code quotation to back up your plan because the code is permissive. It does not list exhaustively all the things that are allowed.

    You are using larger conductors to limit voltage drop. Do the voltage drop calculation adding 10' of smaller, but code approved, wire at the end and notice that the difference is negligible.
    Doing what you suggest is a separate junction box will also avoid any bending space problems with the larger wire.
    Thank you! My thinking was inline with what you suggested... the voltage drop difference will be negligible and easily demonstrated for the inspector (a former employee!!). Was hoping I wasn't missing anything and appreciate the comment. We had already determined to have an oversized wireway above the meter paks and will most likely do the reducing splices there.

    Thank you.

  4. #4
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    Quote Originally Posted by StevenLeuck View Post
    We have a large multi-family mixed use building we are just now bringing out of the ground. We're trying to figure out a solution to the over-sized conductors on too-small lugs. All of our residential units require only a 100Amp loadcenter. We've solved the connection at that end of the feeder by buying 150A rated MLO loadcenters which have lugs good for up to 300KcMIL. However, it's the other end that has me concerned. The meter/main meter packs we're using are Eaton (Cutler-Hammer) and the 2-pole mains will be BR2100 circuit breakers. Submittal sheets say the maximum wire size on their lugs is 1/0. However, due to distances, we have about half the building requiring #2/0 feeders, plus a small handful of them at both #4/0 and #250KcMIL. I've been researching ways to reduce the conductor size to fit on the 1/0 lugs but not finding anything conclusive. Am curious to know what others have done as inevitably, there are others who have run into this before us. I can't find any manufacturers who make a compression reducer that will go from 250 to 1/0. Mechanical lugs are plentiful for this. I'm hoping I can find out from others what they've done in the past. Also curious about code quotation to back us up with the inspector for having 10' of 1/0 AL at the beginning of a #250 AL feeder in case they have a problem with it.
    Use a Polaris connector that goes from the 4/0-250MCM to a smaller jumper wire that will fit the 1/0 lugs:

    http://www.polarisconnectors.com/pdfs/nsi/it_series.pdf

    Using a few feet of 1/0 from that connector in a gutter below/above the meter will not affect voltage drop but a fraction of a %.

    eta: as far as code issues, as long as the 1/0 is suitable for the calculated ampacity and OCPD, you will be fine. A few might want torque values or % fill of your gutter/panel/can housing.

    seta: If you're on a 150A breaker, you'll have to use 1/0 in copper only; AL is good for just 120A.
    Last edited by JFletcher; 08-11-17 at 07:07 PM.
    Electricians do it until it Hertz!

  5. #5
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    Also, you realize that if you use Polaris connectors on both ends and 90*C wire, you are permitted to use the 90*C table for ampacity for the wire between the 2 (but 75*C for the wire from connector to meter and breaker). I know you oversized for VD reasons, just throwing that out there.
    Electricians do it until it Hertz!

  6. #6
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    Quote Originally Posted by StevenLeuck View Post
    We have a large multi-family mixed use building we are just now bringing out of the ground. We're trying to figure out a solution to the over-sized conductors on too-small lugs. All of our residential units require only a 100Amp loadcenter. We've solved the connection at that end of the feeder by buying 150A rated MLO loadcenters which have lugs good for up to 300KcMIL. However, it's the other end that has me concerned. The meter/main meter packs we're using are Eaton (Cutler-Hammer) and the 2-pole mains will be BR2100 circuit breakers. Submittal sheets say the maximum wire size on their lugs is 1/0. However, due to distances, we have about half the building requiring #2/0 feeders, plus a small handful of them at both #4/0 and #250KcMIL. I've been researching ways to reduce the conductor size to fit on the 1/0 lugs but not finding anything conclusive. Am curious to know what others have done as inevitably, there are others who have run into this before us. I can't find any manufacturers who make a compression reducer that will go from 250 to 1/0. Mechanical lugs are plentiful for this. I'm hoping I can find out from others what they've done in the past. Also curious about code quotation to back us up with the inspector for having 10' of 1/0 AL at the beginning of a #250 AL feeder in case they have a problem with it.
    you can buy finger lugs that hypress onto aluminum wire, and have a smaller extrusion to fit under the lug. the good thing is that they provide a permanant connection for aluminum that does not deteriorate over time, nor loosen. they are the only way i will land aluminum conductors onto a breaker. it leads to a connection as good as copper.

    in severely corrosive situations, you can use panduit heat shrink that will give you a permanant waterproof connection. works in a salt air environment.
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  7. #7
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    Reducing wire size is common when you're using much larger conductors for voltage drop. Here's several hundred feet of parallel conductors for a 200 amp ATS.

    Name:  20130206_100136.jpg
Views: 272
Size:  137.9 KB
    Rob

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    All responses based on the 2014 NEC unless otherwise noted

  8. #8
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    Quote Originally Posted by Fulthrotl View Post
    you can buy finger lugs that hypress onto aluminum wire, and have a smaller extrusion to fit under the lug. the good thing is that they provide a permanant connection for aluminum that does not deteriorate over time, nor loosen. they are the only way i will land aluminum conductors onto a breaker. it leads to a connection as good as copper.

    in severely corrosive situations, you can use panduit heat shrink that will give you a permanant waterproof connection. works in a salt air environment.
    One problem he likely runs into though is that there is not enough bending space for a 250 conductor in a meter center compartment that is only rated for 100-125 amps.

  9. #9
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    Quote Originally Posted by JFletcher View Post
    seta: If you're on a 150A breaker, you'll have to use 1/0 in copper only; AL is good for just 120A.
    My understanding is there is 150 amp main lug panel (which will accept his 250 conductors), but the feeder breaker is only a 100 amp breaker and only accepts up to 2/0 conductor. The conductor is larger for voltage drop reasons and not ampacity reasons. Is also likely there isn't appropriate bending space on the supply end even with a reducing device that attaches directly to the conductor.

  10. #10
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    Quote Originally Posted by infinity View Post
    Reducing wire size is common when you're using much larger conductors for voltage drop. Here's several hundred feet of parallel conductors for a 200 amp ATS.

    Name:  20130206_100136.jpg
Views: 272
Size:  137.9 KB
    That picture is extremely deceiving to say the least.

    JAP>

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