Is this cable ok???

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  #1  
Old 03-31-06, 05:27 PM
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Is this cable ok???

Hi everyone,

I will soon be installing a subpanel in my garage, after the pros here told me how/what to do I spoke with the county inspector and he said that aluminum cable is fine as long as I use a rust inhibitor on the connections. I called The HD and they have "2-2-4-6" (that is what the person called it). I understand this to be 2 conductors 2awg (hots), 1 conductor 4awg (neutral), 1 6awg (ground), am I correct on this? Once again thanks to all, your help is much appreciated,

Oz
 
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  #2  
Old 03-31-06, 05:49 PM
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Sounds like 100 amp direct burial mobile home feeder
 
  #3  
Old 03-31-06, 07:22 PM
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Are you wanting a direct burial method or conduit run?
 
  #4  
Old 03-31-06, 08:38 PM
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I presume that 2-2-4-6 is SER cable? Is this an attached garage?

What size breaker do you plan to feed the subpanel with?

The 2-2-4-6 would be BLACK-RED-WHITE-BARE for Hot-Hot-Neutral-Ground. In the SER cable I fed a subpanel with, the red and white were actually black with a red stripe and black with a white stripe.

Definately use No-Lox on the wire. Get a wire brush (it doesn't need to be coarse at all) and brush it on until it penetrates into the gaps between the strands. You can get a small tube which will be plenty for the eight connections you will need to make. I see no reason not to be generous in applying it.

A week or so after you have installed everything, shut the power off and go back and re-torque all the connections. After that, check them yearly.


For my use, I found that a hack saw does a neat job cutting this thick wire...leaves a neater edge than bolt cutters. Besides, I don't have any bolt cutters.
 
  #5  
Old 04-01-06, 04:25 AM
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Hi,

I presume that 2-2-4-6 is SER cable? Is this an attached garage?
Yes it is an attached garage.

What size breaker do you plan to feed the subpanel with?
100A.

"A week or so after you have installed everything, shut the power off and go back and re-torque all the connections. After that, check them yearly" This sounds like a GOOD advise.

Are you wanting a direct burial method or conduit run? None.
It is going thru a crawspace then up to the middle of the wall to the subpanel box.

Thanks again

Oz
 
  #6  
Old 04-01-06, 11:53 AM
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Full size neutral

This constitutes a subfeed, full size neutral 2-2-2-4
allowable ampacity of #2 aluminum SER cable is 75 amps, as you are required to utilized 60 degree temp rating
Article 310-16
You can only use #2 SEU for 100 amps at the Service Entrance
If you want a true 100 amp subfeed, use 1/0 SER
 
  #7  
Old 04-01-06, 12:19 PM
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>> I presume that 2-2-4-6 is SER cable?
> Yes it is an attached garage.
Is it SER cable?

>> A week or so after you have installed everything,
>> shut the power off and go back and re-torque all
>> the connections. After that, check them yearly.
> This sounds like a GOOD advice.

I would like to know why it is advised.

The torques aren't just made up numbers.
They are supposed to be good to hold for the life of the system.

If the conductors can work loose, something else is wrong with the installation.


> It is going thru a crawspace then up to the middle of the
> wall to the subpanel box.

You might need protective conduit.
 
  #8  
Old 04-01-06, 06:26 PM
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Originally Posted by RobertWilber
allowable ampacity of #2 aluminum SER cable is 75 amps, as you are required to utilized 60 degree temp rating
Can you cite a code reference for this?

If I recall, SER is rated for 75° or 90° (75° I think), and 338.10(B)(4) states that I do not apply 334.80 to this cable.

The terminations on the circuit breaker and the lugs of the MLO panel are usually rated at 75°, so a #2 SER would be worth 90 amps, not 75, using Table 310.16.
 
  #9  
Old 04-01-06, 09:12 PM
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Originally Posted by RobertWilber
You can only use #2 [aluminum] for 100 amps at the Service Entrance.
Perhaps in Philadelphia and other localities with such an amendment.

Under NEC 310.15(B), it's 100A as a feeder.





[This does not constitute an endorsement.]
 
  #10  
Old 04-01-06, 11:28 PM
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Well I prefer to do business with my little brother + sister owned electrical supply. But I ventured into home depot this evening and they did not carry SER cable of any size. The only
2-2-4-6 they had was AL mobile home feeder. But I suppose this could vary from location to location.
 
  #11  
Old 04-02-06, 08:47 AM
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Originally Posted by bolide
Under NEC 310.15(B), it's 100A as a feeder.
To expand on Bolide's post, it's 100A if it serves as the service entrance conductors or the main power feeder to a dwelling unit. A subpanel in a garage would not be a main power feeder to a dwelling unit, so you could not apply this table to the original post.

[This does not constitute an endorsement.]
Skittish?
 
  #12  
Old 04-02-06, 09:42 AM
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Whether the table 310.15(B)(6) can be applied to a sub panel is often decided by the AHJ (authority having jurisdiction - inspector folks). The definition of a feeder per the NEC is a conductor between the service equipment and the final branch circuit overcurent device, and a cable between a main panel and sub panel qualifies here. A "main feeder" is defined as a cable between the main disconnect and the lighting and appliance branch-circuit panelboards(s). Many interpret this to mean all the panels as sub panels are not specifically excluded

The AHJs I deal with have so far had no issues with using 2-2-2-4 for feeding a 100 AMP sub panel and I've installed quite a few. As far as I'm conserned, if the AHJ buys it it's OK. If there's no AHJ to interpret the situation then you're gonna have to take an opinion and run with it. It does stand to reason if 2-2-2-4 can feed a 100 AMP residential service there's no reason it can't feed a 100 AMP residential sub panel as well.
 
  #13  
Old 04-02-06, 10:54 AM
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> A subpanel in a garage would not be a main power feeder
> to a dwelling unit

Obviously the panel is a panelboard not a feeder.
How did you decide this?


> Skittish?

No.
 
  #14  
Old 04-02-06, 12:57 PM
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I am not a moderator.

I respectfully request that a discussion of the detailed interpretation of 310.15(B)(6) be carried out in a separate thread. It is sufficient to answer the original posters question as "There is some debate about the rules. Under the most conservative interpretation, your conductors may be protected by a 90A breaker. Using a slightly different interpretation, 100A is acceptable. If you want to be certain of the answer prior to inspection, then ask your AHJ."

bolide, no disrespect, but even if we all agreed that your interpretation was correct, if the AHJ followed the other interpretation than our unanimous option would mean very little.

Furthermore, the original poster asked if a particular cable was 'OK', without specifying additional details. It was only after we asked additional questions that we even knew the requested feeder ampacity. There are quite likely other issues that the original poster does not even know to ask about, which could render this installation incorrect or even dangerous. IMHO it is far better to help the original poster provide for a safe installation than to endlessly debate a single point.

To the original poster: could you describe the entire system that you wish to install, including cable type, locations, circuit breaker sizing, and your locality?

-Jon
 
  #15  
Old 04-02-06, 09:47 PM
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Hi, I'm going to try to explain what I want to do. I want to install a 100A subpanel in my attached garage. The house has a crawlspace and I plan on running cable or conduit thru the crawlspace. I will talk to the county inspector and see if "2-2-4-6" cable (as it was called by the salesperson at HD) is acceptable, this was my original question. The breaker for the subpanel is 100A, distance between
panels is 35 ft aprox, not exposed to the weather, any other factors that I should consider? Thanks

OZ
 
  #16  
Old 04-02-06, 11:08 PM
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Originally Posted by winnie
bolide, no disrespect, but even if we all agreed that your interpretation was correct, if the AHJ followed the other interpretation than our unanimous option would mean very little.
Are you referring to UncleBill?

Rocky Mountain called into question part of a post made by RobertWilber.
I had a look at that post and noticed that it contained another statement that was not an accurate reflection of what the NEC actually states.

My response was strictly a rebuttal to an incorrect assertion about the NEC made by RobertWilber.
UncleBill expounded upon that by stating that he often has installations approved according to the article I indicated.

I simply stated what NEC article (and that a local exception might very well apply to Philadelphia, the only city of the first class in PA).
I specifically did not set forth a stance on its applicability to any AHJ, and certainly not an interpretation. At least I don't see how it's an interpretation. The NEC explicitly does not limit it to service entrances and the NEC does explain what a main feeder is (viz., a feeder from the main).
 
  #17  
Old 04-02-06, 11:22 PM
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Originally Posted by yalipito
I will talk to the county inspector and see if "2-2-4-6" cable (as it was called by the salesperson at HD) is acceptable
Say:

I want to know whether it is acceptable to feed a 100A subpanel in my garage using 100A mobile home cable in conduit from my service panel in my basement.


He should know exactly what this cable is and whether it is permitted.
 
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