Cable tray fill question

I have a question about cable tray fill. It was a question on my code test and I know I got it right but my teacher marked it wrong. I have had two master electricians do the problem and got the same answer I did. I want to go to class prepared to debate my answer so any help is greatly appreciated. The question is:

What size ladder cable tray is needed for 3 500 kcmil 3 350 kcmil and 3 750 kcmil all conductors are THHW compact aluminum wire and are single Single conductors less than 2,000 volts.

Thank you!
 

Smart $

Esteemed Member
Location
Ohio
The forum leaders here want students to show their work, perhaps reasoning, and answer to prove we are not being asked to do their homework or answer test questions...;)


Welcome to the forum. :thumbsup:
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Why don't you show us your work and we will comment on it?

Sorry for the same comment....That is what I get for not refreshing the page after walking away to take a phone call.
 
Here is my work. :)

Here is my work. :)

Chapter 9 Table 5(a)

750 kcmil THWN area = 1.0386 x 3= 3.1158
500 kcmil THWN area = 1.6932 x 3= 2.0817
350 kcmil THWN area = .5281 x 3= 1.5843

total= areas added together = 6.7818 sq in

392.22B(1)(b)

column 1 of table 392.22(B)(1)

8" tray
 

Smart $

Esteemed Member
Location
Ohio
Chapter 9 Table 5(a)

750 kcmil THWN area = 1.0386 x 3= 3.1158
500 kcmil THWN area = 1.6932 x 3= 2.0817
350 kcmil THWN area = .5281 x 3= 1.5843

total= areas added together = 6.7818 sq in

392.22B(1)(b)

column 1 of table 392.22(B)(1)

8" tray
I agree with your answer.

[bold red in quote indicates typo]
 
Njact tests says it's incorrect

Njact tests says it's incorrect

I KNOW it's the correct answer. I just want to go to class prepared to debate. My teacher said use the diameter because the area is "approximate area".... Which yes it does say that but I do not see a different table for exact diameter of compact aluminum THWN.... Nor could he tell me where to find it. And that was the question directly from the test word for word. As all my instructors have said this far.... Jatc stands for just approximate training center because a lot of the questions are felonious and contradict the text. (There are errors in the textbooks as well)
the "correct" answer on the test was 9" cable tray. Now, I have done my research, and in the 2008 NEC 8" cable tray was not an option in the table, so it was either 6" or 9". But both 2011 and 2014 editions have 8" cable tray.

so I am perplexed and upset. I take my grades a bit too serious and I hardly ever get anything less than a perfect score in code class and anything less makes me work harder and generally I end up debating until I prove my point. :ashamed1:

Thank you you very much for your help! Hopefully two master electricians, a previous instructor (who is an inspector and code genius) and your answers will get me my 100%! :angel:
 

Smart $

Esteemed Member
Location
Ohio
... Now, I have done my research, and in the 2008 NEC 8" cable tray was not an option in the table, so it was either 6" or 9". But both 2011 and 2014 editions have 8" cable tray.
...
Could be the instructor is going by the answer key. Also, I know for a fact that some, many JATC tests are questions computer selected pool of questions.... and the answer key is generated at the same time. Could be the answer was not updated after the 2008 NEC edition. What year is the text?
 
Last edited:

Fulthrotl

~~Please excuse the mess. Sig under construction~~
so I am perplexed and upset. I take my grades a bit too serious and I hardly ever get anything less than a perfect score in code class and anything less makes me work harder and generally I end up debating until I prove my point. :ashamed1:
breathe in and breath out. perhaps you just need a perspective adjustment.

it's been a long time since i did JATC tests, but back before the dawn of the
electron, it was pretty simple. maintain a 90% GPA for the entire period of
your apprenticeship, you will get your pay increases on time, and assuming
you get the necessary hours to complete your apprenticeship, your ticket
will look just like everyone else's when you end up signing the book.

the journeyman's test? well, if you have a 90% or better on every single
national JACT test, they can't very well fail you on the journeyman's test.
the national curriculum is what they have to make their case on, and your's
will be fine.

when i sat for the journeyman's test, the apprenticeship instructor provided
the 600 question pool that the 100 questions would be selected from. everyone
freaked out, and studied the questions. i wrote the answer to each question as
a statement. i didn't need to know the questions, i needed to know the answers.
studying questions is dumb and fills up space in your head needed for answers.

then as i was told to take the test in the same state of mind i studied the material,
i stayed up the night before the test, with a quarter ounce of a class II controlled
substance, and a fifth of jack.

took a shower, ate some oatmeal for breakfast, read thru the 600 answer statements
i had in a folder, and took the test. i finished third out of 75 people in my class.

but i used restraint. i didn't eat any mescaline before taking the test. save the
mescaline until after you pass the journeyman's test, and you will do fine.
 

mgookin

Senior Member
Location
Fort Myers, FL
I KNOW it's the correct answer. I just want to go to class prepared to debate. My teacher said use the diameter because the area is "approximate area".... Which yes it does say that but I do not see a different table for exact diameter of compact aluminum THWN.... Nor could he tell me where to find it. And that was the question directly from the test word for word. As all my instructors have said this far.... Jatc stands for just approximate training center because a lot of the questions are felonious and contradict the text. (There are errors in the textbooks as well)
the "correct" answer on the test was 9" cable tray. Now, I have done my research, and in the 2008 NEC 8" cable tray was not an option in the table, so it was either 6" or 9". But both 2011 and 2014 editions have 8" cable tray.

so I am perplexed and upset. I take my grades a bit too serious and I hardly ever get anything less than a perfect score in code class and anything less makes me work harder and generally I end up debating until I prove my point. :ashamed1:

Thank you you very much for your help! Hopefully two master electricians, a previous instructor (who is an inspector and code genius) and your answers will get me my 100%! :angel:
It makes me very angry (said like the line in Pretty Woman) when someone who purports to be qualified to instruct publishes a book with blatant errors. It's a result of incompetence or laziness, both of which should disqualify anyone from being able to publish such materials. I have seen complete garbage written by people with Ph.D.'s. Total garbage. In a university curriculum.

It makes me very AAAAA-NNNN-GGGG-RRRR-YYYY!
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
I KNOW it's the correct answer. I just want to go to class prepared to debate. My teacher said use the diameter because the area is "approximate area"....
Chapter 9 Table 5A is in the code. It is not in an informational annex and the values shown there are the values you use for this calculation.
the "correct" answer on the test was 9" cable tray. Now, I have done my research, and in the 2008 NEC 8" cable tray was not an option in the table, so it was either 6" or 9". But both 2011 and 2014 editions have 8" cable tray. ...
So I expect that just means as others have suggested that the test answers have not kept up with code changes.

However, if that is the case any instructor should accept the correct answer based on the code book that you are using for the class.
 

Fulthrotl

~~Please excuse the mess. Sig under construction~~
Haven't heard that word mentioned for near 30 years. What's the world coming to. :slaphead:
it's been 32 years since i last had anything to do with anything like that.
musta been after i gave it all up, it fell out of favor.

thinking back, the last time i ate anything like that, was a saturday sometime
in 1982, when a friend and i had freeze dried magic mushrooms,
along with jack and chocolate chip ice cream.... for breakfast.

hey. don't judge. several food groups were represented, and we went off roading
afterwards. at least we weren't on a public highway. betcha didn't know that with
the right kind of eyes, you can see the air move, didja?
 
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