2005 NEC Master practice test part 3 question 8

[Jon309]

Why do we revert to 75 C wire rating when THHN is 90 C

 

[jumper]

110.14(C) in most cases.

 

[iwire]

There is no electrical equipment less than 600 volts that is rated for 90 C use.

Breakers, switches, time clocks, receptacles etc are all rated just 75 or sometimes 60 C.

 

[Dennis Alwon]

why do we use 75 c rating when thhn is 90 c

75C is usually used because the termination points are only rated 75C. It is safe to say that most electricians have never used 90C terminations. I have never sen one. Read art.110.14(C)

 

[Jon309]

thanks for the answers. sorry to be a pest but also on part 3 of the practice test question 19 had me scratching my head. can anyone tell me how column c still applies when the ranges in question are 12.4 kw and column c says (not over 12kw)?

 

[charlie b]

Can anyone tell me how column c still applies when the ranges in question are 12.4 kw and column c says (not over 12kw)?

Take a look at the notes below the table. Also, if you change the subject from the original question, you should start a new thread. Also, we are not all going to have the test to which you refer. So we might not be able to understand the questions you are asking, unless you give us more of the question.