|Count your Current Carrying Conductors to get your bundling correction factor.|
|You have to count
your neutrals unless they only
handle unbalanced loads from a multiwire circuit that doesn't contain
non-linear loads. Find your correction factor from the table at
|Find your conductor's maximum capacity.|
|Look at tables
310.16 to 310.20 and find you conductor for the desired location.
Make sure your using the column that corresponds to the temperature rating of your insulation(60c, 75c, ect)
|Find your temperature correction factor.|
|If this conductor
shall be used in a location subject to direct sunlight on or above a
rooftop then you need to add to the ambient temperature according to
310.15(B)(2)(c). At the bottom of
the table find your adjusted ambient temperature. In the column marked
with the temperature rating of your insulation (such as 60c, 75c, ect)
you'll find your temperature correction factor.
Adjusted ambient temperature = ambient temperature + value from 310.15(B)(2)(c)
|Put it all together.|
|Amps you can use
= (Amps of wire at 30c) x temperature correction factor x bundling
Instructions on how to figure out what size conductor to use for a given ampacity
|Everything is the same as above except you need to divide by your correction factors|
'Full Ampacity' = (Amps you need / bundling correction factor) / temperature correction factor
Then find a wire that can handle the 'Full Amps'
Some average outdoor ambient temperatures for selected cities during the period of June to August are shown below. These temperatures are based on ASHRAE Handbook of Fundamentals 2 percent design temperatures and are measured in the shade, not in the sun. ̊F ̊F City City Birmingham, AL 94.0 St. Louis, MO 94.4 Phoenix, AZ 109.5 Las Vegas, NV 107.4 Bakersfield, CA 102.7 Newark, NJ 92.1 Los Angeles, CA 78.6 Albany, NY 87.3 Long Beach, CA 86.9 Islip, NY 87.3 Palm Springs, CA 110.8 Akron/Canton, OH 87.1 Wilmington, DE 90.5 Providence, RI 88.3 Atlanta, GA 92.3 Knoxville, TN 91.4 Chicago, IL 90.6 Houston, TX 96.0 Baltimore, MD 92.5 Charleston, WV 89.7 Boston, MA 89.6
Copies of the Tables are available from the website of Houston Wire & Cable.
Mobile Calculator also works on internet enabled cell phones. Calculate Max Amperes for a Conductor.
Find Conductor to handle a given Load
copywrite & by Jason Wilson