Wire size per 310.16.. which column ???

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craig127

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For years now I have used the 90 degree column to size my conductors. I have always used 2/0 for 200 amp underground feeders
I am being told I have to use 3/0 copper for 200 amps on a small design build we are bidding

The reason I was given is that since the lugs on the panel are only rated 75 degrees c I must use that column to size my conductors.
Has anyone else heard of that???

Even if I do use the 75 degree column the conductors leave a bottom fed panel, go directly underground to the transformer, buried 3 1/2 feet deep. That would make the ambient temp 70 or so degrees. So 2/0 is good for 175 amps in the 75 degree column. Correction factor is 1.05
175 X 1.05 = 183.75 amps. 240.4. B allows me to go up to the next standard size... 200 amp
Am I missing something??
 
Check out 110.14(C) for the temperature limitations for terminals.

Typically you can only use the 90c column of 310.16 for derating purposes.

Chris
 
Finite10 said:
When the lug isn't marked, assume 60 degrees F.
Click to expand...


Not always.

(b) Termination provisions of equipment for circuits
rated over 100 amperes, or marked for conductors larger
than 1 AWG, shall be used only for one of the following:
(1) Conductors rated 75?C (167?F)
(2) Conductors with higher temperature ratings, provided
the ampacity of such conductors does not exceed the
75?C (167?F) ampacity of the conductor size used, or
up to their ampacity if the equipment is listed and identified
for use with such conductors
 
jumper said:
Not always.

(b) Termination provisions of equipment for circuits
rated over 100 amperes, or marked for conductors larger
than 1 AWG, shall be used only for one of the following:
(1) Conductors rated 75?C (167?F)
(2) Conductors with higher temperature ratings, provided
the ampacity of such conductors does not exceed the
75?C (167?F) ampacity of the conductor size used, or
up to their ampacity if the equipment is listed and identified
for use with such conductors
Click to expand...

True. That's a requirement for equipment. Over 100A it needs to have 75 degree terminations provided - and needs to be marked 75 degrees F.
 
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