Exam conditions, conductor sizing with 110.14c

[Jbudgy]

For a state exam, when a question doesn't mention termination temperature rating, does one assume 75degree terminations when sizing conductors? or would you apply 110.14c and restrict the ampacity to 60degree column for loads under 100 amps.?

It was previously my belief that we are to assume all terminations are 75 degrees unless told otherwise, although I cannot find that direction in the (MN) dli exam study guide. I understand other state exams might provide different direction, but guessing that its generally a similar practice.

My initial reaction was to not apply 110.14c unless a question says the terminal temperature is not known.

Please correct me if Im wrong.

 

[Carultch]

For a state exam, when a question doesn't mention termination temperature rating, does one assume 75degree terminations when sizing conductors? or would you apply 110.14c and restrict the ampacity to 60degree column for loads under 100 amps.?

It was previously my belief that we are to assume all terminations are 75 degrees unless told otherwise, although I cannot find that direction in the (MN) dli exam study guide. I understand other state exams might provide different direction, but guessing that its generally a similar practice.

My initial reaction was to not apply 110.14c unless a question says the terminal temperature is not known.

Please correct me if Im wrong.

If nowhere in the exam, do they specify that the terminals are listed and marked otherwise for 75C, then you'd have to assume 60C to be correct. The exam might very well be incorrect, and assume 75C without telling you.


Bear in mind that they might have a master statement, as opposed to a statement within each problem, specifying 75C.

 

[infinity]

If not given terminal information then I would assume that if it met the following conditions it's 75° C.

110.14(B)(1)(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 iden-
tified for use with such conductors

 

[mwm1752]

OP was asking about under 100 amps or if the question is based on derating - -derate from the conductors highest temp rating -- could be the wiring method that rates the conductor temp as in MN type or SER under certain conditions. do you remember the wording of the question?

 

[Carultch]

OP was asking about under 100 amps or if the question is based on derating - -derate from the conductors highest temp rating -- could be the wiring method that rates the conductor temp as in MN type or SER under certain conditions. do you remember the wording of the question?

OP mentioned nothing about derating.

OP is interested in the rule that applies before you even think about derating. Terminals 100A and less are by default rated for 60C, and over 100A by default rated for 75C. Unless listed and labeled otherwise. The burden of proof is on the one who believes the terminals are rated for something other than the default 60C, for 100A and less. And thus the exam must specify, either on each applicable problem, or as a master statement. Even though the 60C rule is more academic than practical, since most modern terminals are rated otherwise for 75C.

 

[infinity]

I believe that he's referencing something like this, if the terminal temperature value is not given which one would you use?

 

[Carultch]

I believe that he's referencing something like this, if the terminal temperature value is not given which one would you use?

The NEC clearly states that using the 75C column for the <=100A requires proof of the product being rated for it. I.e. the exam must specifically state it, if they want that to be the correct answer.

I'm sure it occasionally slips through the cracks, when the answer key authors ignored this fact, and assume you'd use 75C like you do in practice.

 

[mwm1752]

seem like if you cannot verify the termination rating(<= 100 amps) then you would default to the most restrictive 60C -- may have been part of the intent of the question -- & yes conductor temp rating does fit into the equation - we do not have the exact wording of the question for true analysis.