Wire Type

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  #1  
Old 11-07-05, 03:42 AM
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Wire Type

What wire specification should I look for if I need 4/3 cable in direct bury aluminum? I am looking to run a sub panel out to a shed that's 150 feet away from the service panel. The voltage drop requires at least 4 AWG if I use AL and AL is the cheapest way to go, 6/3 UF copper is 2.30 a foot. Any recommendations?

Thanks

Leslie
 
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  #2  
Old 11-07-05, 08:59 AM
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We use some stuff that we have been calling "cablecon." This is pretty neat stuff. It is prescoped Al wire in poly conduit. If you have any sort of critters that dig in the ground this is good stuff. We put miles of it in the ground every year. Contact a local Valley Center Pivot dealer, other center pivot dealer, or electric wholesaler they might just have the amount you need left over on a long reel.

We used to put a lot Al in the ground without conduit but got sick of making emergency splices all the time. Those darn gophers just tear the stuff up.

You might expect to pay $1.69/ft from your local Valley Irrigation Dealer.
 

Last edited by rshackleford; 11-07-05 at 01:23 PM.
  #3  
Old 11-07-05, 12:17 PM
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Most manufacturers do not make UF-B cables in larger than #6. You should be looking for USE (Underground Service Entrance) cable in #4 aluminum. I see a price online of $0.30/ft per conductor without shipping. Your cable should be at least 24" deep, and make sure there aren't any rocks in the trench fill.
 

Last edited by ibpooks; 11-07-05 at 12:28 PM.
  #4  
Old 11-08-05, 04:06 AM
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Is USE like a standard UF type */3 cable in that it has three conductors and a EGC wrapped with the outer cable cover? Or will I need to run a seperate EGC? If I use #4 AL can I use a #8 EGC?

Leslie
 
  #5  
Old 11-08-05, 05:13 AM
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1) I strongly advise you to _not_ direct bury aluminium conductors. Either bury a conduit or use copper. If there is the slightest break in the insulation with an aluminium conductor, water will get in, the conductor will corrode around the break, and then you have to pull the conductor out. Having to dig the trench a second time will eat up any savings between aluminium and copper, but IMHO conduit is the best approach (conduit and copper is the absolute best, but there is such a thing as going too far, and you have to make that choice)

2) Conductors to a subpanel are generally sized using table 310.16, although some inspectors will permit cable sizing using table 310.15 Make sure that you are using the appropriate table to select conductor size

3) The equipment grounding conductor is generally sized using table 250.122, with the proviso that if you _increase_ the size of the circuit conductors for _any_ reason (specifically voltage drop), then you must proportionally increase the size of the equipment grounding conductor.

4) Since you've said that you are increasing the size of the conductors, then you must also increase the size of your EGC, so you will need to be very careful about selecting cable assemblies . You've never specified the breaker trip rating, calculated load current, desired voltage drop, etc. so we can't tell you if your conductor sized are reasonable.

5) 'Type USE' cable is available as cable assemblies or as individual direct bury conductors.

-Jon
 
  #6  
Old 11-08-05, 06:40 AM
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We bury alum all the time and most of the worlds power is run on it, its what the power company uses. I bought 2-2-2-4 at HD the other day, they were cheaper than the house. For long runs I like this on a 60A, the number 4 is too small. If there ever would be a problem it can be dug up, trenches are dug every day too, ask my men,, ha BTW, I paid $ 1.10 ft. I have several thou ft of it, never had a gopher problem, do they dig much at legal burial depth?
 
  #7  
Old 11-08-05, 07:08 AM
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Conduit is a bit like preventative maintenance. We install conduit because our busiest time of the year is when our customers are using their systems. We donít have time to go and dig up line bread after line break. So we make our service department look good by not needing to send them out. If you donít mind sweating youíre a** off in a trench because you didnít want to spring for some conduit, then donít lay pipe. Al wire will get nicks in the insulation and these will cause it to fail. The Al wire that power companies install today has a much different insulation then USE wire. I just canít express how frustrating it is to have continual line breaks. Splices arenít cheap either. The materials alone for a good, waterproof splice could be as much $30-$50.
 
  #8  
Old 11-08-05, 07:46 PM
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I am running a 150 foot line from the service panel to a 100 amp breaker type sub panel. At the main panel I will be using a 60 amp breaker for circuit protection. The voltage drop needs to be suitable to run basic electric tools, battery chargers, as well as the lighting circuits. As far as a demand load goes it will be basically two 15 amp general purpose circuits, two 15 amp lighting circuits, and the future capability to have a 240 circuit (no more than 20 amps). There will be no heaters, welders, kilns etc.. Just a basic storgae shed for yard equipment with the capability of working in it at night. The voltage drop calculator showed a workable voltage drop with 4 AWG AL, 60 amps, 240 volts at 150 feet. Again, I want to do it right the first time but I want to do it right and save as much money as possible.
 
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