Need 4/3 romex wire

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  #1  
Old 08-18-05, 07:57 AM
bobbason
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Need 4/3 romex wire

Hello, I am adding a subpanel to my basement, it is rated at 100Amps, I have a 100 Amp breaker that I plan to connect to my main panel ( rated 200Amps). Here is my problems. I found that Romex #4 is rated at 100 Amps, my problem is that my local Home Depot, Lowes, and all local electric suppliers do not sell this cable cut to order. I only need 25 - 30 feet at the most. One local electrical supplier has it but in 125 ft rolls. I have serached the net and even this site electrical supply page. My question were can I order just 30 or 50 feet at the most of romex, nm 4 /3 for hooking up my subpanel. Also if it matters I am in metro Atlanta , Georgia area. Thanks....
 
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Old 08-18-05, 08:04 AM
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The amperage rating of #4 copper is not just one number. The 100-amps you quoted is for ideal conditions that never exist in practice. Furthermore, when using cable assemblies, other factors come into play.

Without going into all the gory details, the bottom line is that you need #3 for 100 amps if using individual conductors, or #2 if using NM cable.
 
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Old 08-18-05, 08:50 AM
bobbason
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Point taken, OK then where can I get 2/3 romex cables ? I know that Home Depot, Lowes carries 2-2-2-3 AL cable for service entrance. Can this be used instead?
 
  #4  
Old 08-18-05, 09:17 AM
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I would suggest your look into Copper SER cable to feed your sub-panel.
http://appprod.southwire.com/Product...prodcatsheet11
We call it sub-feeder in my area. The only way you can use #4 Copper SER at 100 amp rating is if you get approval from your local inspector. In my area we are allowed to use a table in NEC article 310 that lets us treat it as a 100 amp rated cable, but only with local authority approval. Otherwise you would do as John has mentioned.
My other question is do you really need 100 amps for the basement? In most cases a 60 amp feed is more than you will ever need. So you might consider feeding the panel 60 amps with 6/3G. I realize this poses a problem since you already have the 100 amp breaker but maybe you can take it back if purchased new.
 

Last edited by Roger; 08-18-05 at 02:21 PM.
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Old 08-18-05, 09:17 AM
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#2 aluminum cable is not allowed for a subpanel feed by the NEC (okay, some people think it is depending on how you interpret a few controversial key words). Nevertheless, many inspectors do in fact allow #2 aluminum cable to serve as a 100-amp subpanel feeder. Best check with your inspector before proceeding. And be sure to let us know what he says.
 
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Old 08-18-05, 09:21 AM
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To add to Roger's comment, 100 amps is a whole heck of a lot for a basement (unless you're doing pottery firing or very serious welding down there). Note that just because you are using a panel rated for 100 amps does not require that you use a 100-amp feeder. A 100-amp-rated panel can be used for anything up to and including 100 amps. The job will be a lot easier and cheaper if you decide that 60 amps and 6/3 cable (which provides up to 14.4 kilowatts) is enough.
 
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Old 08-18-05, 11:06 AM
bobbason
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Well no plans for pottery firing but I did want to make sure I don't need to redo this. It is possible that I would need to connect a stove, heat pump, dryer, 15 amp bedroom, 20 bathroom, connected to the panel. If the money is right , one day even a Jacuzzi. So for right now I could get by with the 60 Amp circuit but I would rather take the time and cover all the bases now. As for using 4, 3, or even 2 for the matter my original question still holds, where can I purchase just 30 feet of 2/3 NM? I can see Southwire makes the cable but they sell in rolls of 250, 500, etc. Thanks again...
 
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Old 08-18-05, 12:04 PM
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Is 1-1/4" PVC conduit with individual conductors not an option? Might end up being cheaper than special ordering cable.
 
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Old 08-18-05, 12:48 PM
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IMHO you will be far better off running THHN conductors in conduit. #2 wire is thick...and #2-3 with ground cable is a bear.

If you use cable, you are required to use the 60C ampacity, but if you use individual THHN conductors, you can probably use the 75C ampacity (this depends upon the terminations); at 100A, this means the difference between #2 and #3 wire, so you can save simply on the amount of copper used.

Something to keep in mind is that the use of larger cables varies considerably by location; one time of wire will be very common in one place, and unheard of someplace else. Rather than fixating on NM cable, you should call the local electrical supply houses, and find out what is common for your application. Some possible materials:
1) You can use SER cable. Note that most SER is aluminium; if you use aluminium conductors than you need #0 gage.
2) You can use THHN or XHHW conductors in conduit as above.
3) You can use MC cable. Probably expensive and not viable, but it may be something that is very common in your area, and thus available and cheaper.
4) You can use aluminium THHN or XHHW conductors in conduit, but you will need to use thicker wire, eg #1 or even #0.

But if you want to buy 2-3 NM, you can try dale electric http://www.dale-electric.com/detail....3%20NMB%2DREEL They are in New York state, since shipping will be as expensive as the wire.

Note on wire sizing: NEC table 310.16 is what is IMHO the correct wire sizing table to use for subpanels. From this you will learn that for a 100A feed you could use #3 THHN copper single conductors in conduit, #2 NM-B copper cable, #1 THHN aluminium single conductors in conduit, or #0 aluminium conductors in cable. Given that Lowes has 2-2-2-3 Al cable, they may have 0-0-0-X Al cable or 0-0-2-X Al cable, which would be sufficient for this 100A feeder.

NEC also has table 310.15(B)(6) which is used to size the _main_ feeders for houses. _Some_ inspectors permit its use for subpanels in houses. At issue is that table 310.15(B)(6) gives some leeway for the fact that in homes the circuit will not generally be used at full capacity, so it permits the use of smaller wires. If you are permitted to use this table you can use #4 THHN copper single conductors in conduit, or #4 copper conductor is _specific_ cable types (eg SER cable, but _not_ NM cable), or #2 aluminium (eg the 2-2-2-3 Al service entrance cable that you mention above) You should check with your inspector to see if using this cable is sufficient for a 100A feed to a subpanel, because if it is, then this is probably your best bet.

-Jon
 
  #10  
Old 08-18-05, 07:53 PM
JBRacing
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Try to see if the industrial suppliers have 4/4 "cab tire" wire. Not sure if there is such a thing,I know there is 6/4 though.(the ground is shielded) Big money but might be more readily available in the length you need.
 
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Old 08-19-05, 05:12 AM
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Actually, this is one of the few wire types that would be stocked at an electrical supplier that he _couldn't_ use.

Cabtire is one of the names used for 'hard service flexible cord', and flexible cord is explicitly prohibited for use in the permanent wiring of a structure, except is a very few listed circumstances. It is not appropriate for this installation.

http://www.wirecableandcords.com/Cabtire.html

-Jon
 
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Old 08-19-05, 08:55 AM
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Bob I'm surprised that a local electrical contractor supply wont sell this to you by the foot. Most of our suppliers in my area sell sub-feeder by the foot and will cut it to your needs. The suppier I use though does not mail order.
As Winnie says things are different from one area of the country to the other.
You try just giving an electical contractor a call or talk to one of the local electrical services they might work something out with you.

Occassionally I order from these guys and have had no complaints, they will sell wire by the foot. However, you arent going to find NM-B larger than #6 awg it is very rare. Try to get Copper SER. You may have to give them a call about SER in copper. Here is the link.....
http://www.electricsupplyonline.com/prod/wire.php
 
  #13  
Old 08-19-05, 12:55 PM
bobbason
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Thanks for all the advise, I am headed to Lowes today to see if they have the 0-0-0-X AL. I will also check if running single cables will be cost effective ( probably not). The link for Dale electrical supply does sell the cable I originally was looking for but at 3.00 a ft comes out to $90 bucks, so agagin as mentioned above just getting what is used locally will prbably be the best option. thanks again Bob.......
 
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