Ampacity Exam question

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chicagosparky

Member
Location
Chicago, IL
Pulling my hair out here & there's not much left. Have a practice exam question: What is the maximum allowable amperage for a #1 AWG Copper THHN conductor. The answer provided is: 110 Amps
But, when I go to Table 310.15(B)(16), look down the THHN column, 145 is listed. What am I missing?
 

texie

Senior Member
Location
Fort Collins, Colorado
Occupation
Electrician, Contractor, Inspector
I'm with David. But in my view it's not a valid question if you don't know the conditions of use. After all, the 60 degree limit would only apply to a breaker that is not marked 75 degree and most are today.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Well without any other info you would have to use the 60C column. I think the question is valid.

(1) Equipment Provisions. The determination of termination
provisions of equipment shall be based on 110.14(C)(1)(a) or
(C)(1)(b). Unless the equipment is listed and marked otherwise,
conductor ampacities used in determining equipment termination
provisions shall be based on Table 310.15(B)(16) as
appropriately modified by 310.15(B)(7).

(a) Termination provisions of equipment for circuits
rated 100 amperes or less, or marked for 14 AWG through 1
AWG conductors, shall be used only for one of the following:
(1) Conductors rated 60°C (140°F).
(2) Conductors with higher temperature ratings, provided the
ampacity of such conductors is determined based on the
60°C (140°F) ampacity of the conductor size used.
(3) Conductors with higher temperature ratings if the equipment
is listed and identified for use with such conductors.
(4) For motors marked with design letters B, C, or D, conductors
having an insulation rating of 75°C (167°F) or
higher shall be permitted to be used, provided the ampacity
of such conductors does not exceed the 75°C
(167°F) ampacity.
 
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