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Old 01-04-2010, 07:28 PM   #16
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Quote:
Originally Posted by codeone View Post
Table 310.16 From the NEC.
From the 75 degree column.
The 90 degree column is only for derating purposes. Have never seen anyone get a UL listing for 90 degrees C.
You won't mislead me. I'm a Master Electrician. Try reading 110.14 for the termination provisions. This is another case where a DIY finds one table (in this case 310.16 and thinks he knows the proper overcurrent protection). In reality, there are about 20 different rules that cover the proper overcurrent protection for a wire size including:

the cable type
the terminations
the bundling
the derating
the temperature corrections
motor allowances
compressor allowances
taps


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Old 01-04-2010, 07:34 PM   #17
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So, with that out of my system, I should answer the OP's question. UNLESS the terminations at both ends are rated for 75 degrees, the correct column to use is the 60 degree column and you need #2 copper for 100 amps (using the next largest OCPD rule). You also can never use anything but the 60 degree column for Romex and UF cable, regardless of the terminations.

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Old 01-04-2010, 07:34 PM   #18
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You won't mislead me. I'm a Master Electrician.
Mark
Think very highly of yourself.

Your not the only one with Liscenses and Certifications.

Have a nice day.
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Old 01-04-2010, 07:36 PM   #19
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Originally Posted by codeone View Post
Think very highly of yourself.

Your not the only one with Liscenses and Certifications.

Have a nice day.
Yeah. I do. Am I right or not? In my business people die based on me being right or wrong. I see about one or two fires a month that are mostly due to DIY/Handman work. I always strive to only provide information if I'm at least 99% sure that I'm right. This is important stuff.

Mark

Last edited by busman; 01-04-2010 at 07:39 PM.
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Old 01-04-2010, 07:37 PM   #20
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Quote:
Originally Posted by busman View Post
So, with that out of my system, I should answer the OP's question. UNLESS the terminations at both ends are rated for 75 degrees, the correct column to use is the 60 degree column and you need #2 copper for 100 amps (using the next largest OCPD rule). You also can never use anything but the 60 degree column for Romex and UF cable, regardless of the terminations.

Mark
Wasnt talking about NM the proper term for Romex (which is a trade name) or UF cable.

Also today most all of your terminations are rated for 75 degrees.
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Old 01-04-2010, 07:38 PM   #21
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Yeah. I do. Am I right or not?

Mark
Not necessarily.
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Old 01-04-2010, 07:42 PM   #22
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So - what did I say that was incorrect?? Did you ask what the wiring method was?? What the ambient temperature conditions were? No. You just jumped right to the 75 degree column. I don't know how the OP could have got the install wrong.

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Old 01-04-2010, 08:04 PM   #23
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Originally Posted by busman View Post
So - what did I say that was incorrect?? Did you ask what the wiring method was?? What the ambient temperature conditions were? No. You just jumped right to the 75 degree column. I don't know how the OP could have got the install wrong.

Mark
With your experience then you would know that #3 does not come in NM cable. Also UF #3 does not come in a cable form.
I dont know of any equipment (panels) that are rated at 60 degrees today.
If you noticed I asked for more info to give a proper answer. I may not have asked all the right questions. But others started asking and discussing other aspects in this thread.

Now if you look at the post the OP last sent you will also notice he could wire this sub panel at about 60A with his load. And thats only a ball park answer.

Yes one question would be to ask what his main panel terminations are rated or approx how old it is.
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Old 01-04-2010, 08:17 PM   #24
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My apologies if my answer was overly abrasive. I do get very tired of seeing damage/heartache due to partial knowledge of the NEC. I'll be the first to agree that the information is not ALL IN ONE PLACE and that there are not pointers to all one needs to know. That's the nature of the beast.

What really got me going originally was the implication that the grounded conductor could be reduced in size.

This is both complicated and important information that is the result of many thousands of fires and deaths worth of learning. It seems that CodeOne has a good grasp of the rules, but I'm not sure that came thru for the OP.

I still contend that only with a COMPLETE understanding of the OP's plan (including wiring method, terminations, and ambient temps) can a correct answer be given, and we still don't have that.

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Old 01-04-2010, 08:23 PM   #25
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Quote:
Originally Posted by busman View Post
It seems that CodeOne has a good grasp of the rules, but I'm not sure that came thru for the OP.

I still contend that only with a COMPLETE understanding of the OP's plan (including wiring method, terminations, and ambient temps) can a correct answer be given, and we still don't have that.

Mark
True Point On needing the OP's plan. Or better yet not only the plan but his equipment.

Like I stated before I was responding to anothers reply which does get things confused sometimes.

I dont normally tout credentials espically mine. I do make mistakes. Also no one can know everything about the NEC. Always changing being refined.
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Old 01-04-2010, 08:29 PM   #26
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With your experience then you would know that #3 does not come in NM cable. Also UF #3 does not come in a cable form.
Not to kill the dead horse, but a common installation for the OP would have been SER cable which is required to meet the NM cable 60 degree requirement when used in interior applications and Southwire does make in a 3-3-3-5 copper cable.

The OP could use Southwire 2-2-2-4 SER Cable.

Respectfully,

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Old 01-04-2010, 08:34 PM   #27
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I think many assume that new equipment & 75 degree rating when posting
There was a big discussion on another thread about it
One person stated that you had to use the 60 column unless you could prove everything was 75 rated

And of course heat could be an issue in a walk up attic

Usually the more people looking at a question the more thorough an asnwer is provided



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Old 01-04-2010, 08:34 PM   #28
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Quote:
Originally Posted by busman View Post
Not to kill the dead horse, but a common installation for the OP would have been SER cable which is required to meet the NM cable 60 degree requirement when used in interior applications and Southwire does make in a 3-3-3-5 copper cable.

The OP could use Southwire 2-2-2-4 SER Cable.

Respectfully,

Mark

Mark.,

I know you are famuair with the SER cable however the 2-2-2-4 do come in both alum et copper verison so just give you a head up and with larger SER cable it more common to find them in alum verison than copper verison due the cost.

Merci,Marc
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Old 01-04-2010, 08:35 PM   #29
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Quote:
Originally Posted by busman View Post
Not to kill the dead horse, but a common installation for the OP would have been SER cable which is required to meet the NM cable 60 degree requirement when used in interior applications and Southwire does make in a 3-3-3-5 copper cable.

The OP could use Southwire 2-2-2-4 SER Cable.

Respectfully,

Mark
Yes It does not always available in most areas because of cost.
Also that is in the 60 degree column in the 2008 NEC.
Some places still use the 2005 or earlier which did not have this requirement.
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Old 01-04-2010, 08:36 PM   #30
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What happened to my post? Now I'm really lost. My service is a 100 amps now. Can my subpanel be 100 amps? Like I said 1-750 watt heater and 1-1500 watt heater both 120v. And about 7 lights and 10-12 outlets. And what size wire from the main to the sub? I'm going to finish the attic for a little home theater. And rewire the rest of the up stairs also. I still have some knob and spool.

Last edited by Kurt1968; 01-04-2010 at 08:43 PM.
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