Help In Understanding Table 310.16

Status
Not open for further replies.
ALLELECTRIC95

ALLELECTRIC95

Member
Hi,

I work as an office assistant to an electrician and I sometimes help him look for stuff in the code book. When I can't find something or figure it out I can always count on you guys to help! I was looking through the book recently trying to figure out wire size requirements and acceptable applications when I came across the confusing table 310.16 on page 314 of the NEC 2008 hanbook (blue back). Can someone.... anyone help me understand this? I don't understand the ambient temperature, the difference in the columns, or......... Anyway what sparked this confusion was the acceptable use of 2/0 aluminum for service feeders in a single phase 150amp service. If you look on the prior page 313 table 310.15(B)(6) 2/0 is acceptable..right? however, if you look at table 310.16 the water gets a little murky. Can someone explain this table to me. How does ambient temperature some into play, which column should I be focused on, how do I determine which is applying to my application? Is this table indicating the use of 2/0 in a 150amp service is acceptable with temperatures up to 194F? I guess I will stop here because I think you get the hint that I have no clue how to interpret this table. I realize it may take writing a small book to explain this to me but if you would take the time I would be very grateful!

Thanks in advance.
Annette
 
A conductors' ampacity is based not only on the insulation (RW, THW, THHN etc.) & material (copper v. aluminum), but the temperature it is installed in. As wire heats up, it has more resistance. Therefore, it's ability to carry current is diminished. So to prevent damage to the insulation, it's ampacity is reduced according to the temperature.

T310.15(B)(6) is not a replacement for T310.16. It is to be used only in certain dwelling applications. Read Article 310.15(B)(6) for details.
 
What type of wire is the 2/0 AL? THHN, THWN, dual rated?
Overhead drop or underground feed? Sunlite resistant or wet location?
individual conductors or SE or USE?
 
It must be nice to have an assistant to look all this stuff up for you. Dose he take you on the job sites to argue code violations with the inspector?:D :D :D
 
I would be nice if he would send you to apprentice school so you can learn even more than just deciphering 310.16.
 
i think she /he is fine but needs own screen name.Something is missing in this picture why the master needs this much help.But welcome anyways your in the field the way i see it.
 
Jim W in Tampa said:
i think she /he is fine but needs own screen name.Something is missing in this picture why the master needs this much help.But welcome anyways your in the field the way i see it.
Click to expand...

Ever ask a question here because your code book is in the truck at work?:cool:
 
chris kennedy said:
If your truck is at work, and your book is at work, where's Waldo?
Click to expand...
Jim W in Tampa said:
The master past the test and needs help here ? OUCH
Click to expand...

You guys miss the point..... There's been several people here who ask a question (Masters, J-levels, mechanics, whoever) because their codebook is not handy. Heck, some guys here are too lazy to go out into their own driveway to look it up. Maybe that what happen with the OP.... some field electrician lost/forgot/dropped his codebook in the sewer.

What's the quickest way to find something out? Maybe call someone in the office to look it up there.
 
480sparky said:
Heck, some guys here are too lazy to go out into their own driveway to look it up.
Click to expand...
Maybe I'm too busy cooking.


What's the quickest way to find something out? Maybe call someone in the office to look it up there.
Click to expand...
Thats classic.:roll:
 
480sparky said:
Heck, some guys here are too lazy to go out into their own driveway to look it up.
Click to expand...

Are you spying on me?? I just sat back down from a trip outside. :D

480sparky said:
What's the quickest way to find something out? Maybe call someone in the office to look it up there.
Click to expand...


When in doubt, ask. No shame in that. :)
 
ALLELECTRIC95 said:
Hi,

I don't understand the ambient temperature, the difference in the columns, or......... Anyway what sparked this confusion was the acceptable use of 2/0 aluminum for service feeders in a single phase 150amp service. Is this table indicating the use of 2/0 in a 150amp service is acceptable with temperatures up to 194F?
Click to expand...

The question is good. Your asking do the ambient temperature derate factors of table 310.16 apply to the table 310.15(B)6 ratings. I would say yes, and you would apply it to the conductor type insulation column.

I'm not sure where this situation would come into play. These temperature ratings are typically applied inside of buildings.
Rick
 
Status
Not open for further replies.
Top