I am currently studying 4 my masters test and have been confused why all of the questions have answers referring to the first table at 30 degrees C and why the second table 40 degrees C is not applicable in the answer description I cannot figure out what application I would use the second table for while determining conductor ampacity. And why it always always seems to use 30 degrees Centigrade.
Table 310.15 B.2.a. Or 310.15b.2.b.?
- Thread starter Tomcdi03
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mbrooke
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It goes to other tables in 310 which are not used in your case, like type Z conductors. Just put an X through the table.
mbrooke
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If curious, look at 310.15(B)(18), 310.15(B)(19), 310.15(B)(20), 310.15(B)(21), 310.60(C)(4), and so forth...
These tables are based on an ambient of 40*C, and reserved for special applications like high temperature wire, wire on a messenger, overhead conductors, conductors over 600 volts, ect... stuff that a typical electrician does not deal with or finds in normal in wall building wiring.
310.15(B)(16) on the other hand has your typical wire types and is based on 30*C ambient, thus we use table Table 310.15(B)(2)(a) for ambient temperature correction.
I know, that giant second table screams use me instead :lol:
These tables are based on an ambient of 40*C, and reserved for special applications like high temperature wire, wire on a messenger, overhead conductors, conductors over 600 volts, ect... stuff that a typical electrician does not deal with or finds in normal in wall building wiring.
310.15(B)(16) on the other hand has your typical wire types and is based on 30*C ambient, thus we use table Table 310.15(B)(2)(a) for ambient temperature correction.
I know, that giant second table screams use me instead :lol:
kwired
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Code doesn't use the words "special circumstances" but as has already been said look carefully at titles of tables and temp ratings of conductors in those tables as well as ambient temp the table is based on.
Majority of what we do with typical "building wiring" is all from conductor types and conditions associated with T310.15(B)(16) which only has 60, 75, and 90 C conductor types and is based on 30C ambient.
Unless you have a high temperature conductor, single conductors in free air, or other somewhat out of ordinary application you don't even need to think about those other tables or the 40C ambient temp correction factors.
mbrooke
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After 310.15 B 17, the tables themselves show the conductors, temps, ect.
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