Exam question about RMC (rigid metal conduit)

[Kam1]

Hi

Im new to the forums. I was going through an exam and I had this question come up and I had no clue how to answer the question. I wanted to know if someone would know the answer to the question and would tell me where to find it.


Question:
How many feet can you run a vertical single run of RMC (Rigid Metal Conduit)?

A. 25ft
B. 50ft
C. 100ft
D. None of the above

 

[Dennis Alwon]

I would say D as the vertical raceways is dependent on wire size not pipe size. Look at Table 300.19(A). I don't see anything in art. 344 restricting verticle runs other than how often it should be supported.

 

[cadpoint]

Welcome to the Forum. :thumbsup:

 

[rbalex]

Welcome to the Forum. :thumbsup:

Indeed

It is obviously a trick question because the raceway type is irrelevant. But it is still a poorly worded question if the OP question cited is accurate. It should be something like: What is the maximum length permitted for a single vertical run of RMC (Rigid Metal Conduit)? The answer is still in 300.19(A).

 

[Kam1]

Thank you very much for all your help. Now I understand where this question came from. I knew it was a tricky question. I ended up going with 100ft, but from the response from you guys I feel it is "none of the above". I'm glad I joined this forum.

 

[Strife]

I would say "D", because there's no limit on how many feet you can run a conduit vertically. You would need boxes (to install wire supports) every so many feet depending on the wire size and type. But even with boxes we're still talking ONE "vertical run", so the answer is definitely "D"

Hi

Im new to the forums. I was going through an exam and I had this question come up and I had no clue how to answer the question. I wanted to know if someone would know the answer to the question and would tell me where to find it.


Question:
How many feet can you run a vertical single run of RMC (Rigid Metal Conduit)?

A. 25ft
B. 50ft
C. 100ft
D. None of the above

 

[Strife]

I agree on being a trick question, but I disagree on being poorly formulated(allthough my first impression was that as well).
No matter how many boxes I install for wire support, it's still ONE vertical run. So the answer is unlimited. So by elimination, none of the above.
I had a great teacher in math that told me:"if a variable is not defined in an equation...DON'T ASSUME IT".

Indeed

It is obviously a trick question because the raceway type is irrelevant. But it is still a poorly worded question if the OP question cited is accurate. It should be something like: What is the maximum length permitted for a single vertical run of RMC (Rigid Metal Conduit)? The answer is still in 300.19(A).

 

[rbalex]

I agree on being a trick question, but I disagree on being poorly formulated(allthough my first impression was that as well).
No matter how many boxes I install for wire support, it's still ONE vertical run. So the answer is unlimited. So by elimination, none of the above.
I had a great teacher in math that told me:"if a variable is not defined in an equation...DON'T ASSUME IT".

I agree with both your previous analyses, with one caveat. Your assertion that ?vertical run? is unlimited will depend on whether you believe a box is a fitting or not. An argument could be made either way. The definition of virtually any rigid raceway ONLY includes the couplings and fittings as part of the actual wiring method and Art 314 spends a fair amount of time differentiating between the various enclosure types. However, most boxes still fit comfortably within the definition of fitting. I still think the question could have been worded better, but it ain't worth the time to argue too much about it. (We?ve all agreed D is the answer )

 

[Smart $]

I would say "D", because there's no limit on how many feet you can run a conduit vertically. You would need boxes (to install wire supports) every so many feet depending on the wire size and type. But even with boxes we're still talking ONE "vertical run", so the answer is definitely "D"

I agree on being a trick question, but I disagree on being poorly formulated(allthough my first impression was that as well).
No matter how many boxes I install for wire support, it's still ONE vertical run. So the answer is unlimited. So by elimination, none of the above.
I had a great teacher in math that told me:"if a variable is not defined in an equation...DON'T ASSUME IT".

First, a run of "conduit" terminates at each box. The run of conductor(s) in the conduit may be longer.

Second, a properly-supported vertical run of conduit is unlimited... but only if it is left empty.

As soon as wire is put in it, the maximum length of the run is limited, per 300.19, to 200ft for 6 thru 1/0 AWG AL/CCAL wire.

As worded, "D" would be the best answer, though "All of the above" would have been more appropriate wording. After all, if the vertical conduit run could be 200ft, doesn't that also cover running it 25, 50, and 100 feet???

 

[Strife]

So you're proving what my teacher taught me:
"if a variable is not defined in an equation...DON'T ASSUME IT".

Why assume conductors if the equation doesn't include said variable?

You said it best:"Second, a properly-supported vertical run of conduit is unlimited... but only if it is left empty. "

Did the question include the wire variable? So why do you assume it?
The question was about "vertical run of conduit", no conductors given, so yes, it's about being an empty conduit.
Trick question? Sure.
Poorly formulated? You answered it.

First, a run of "conduit" terminates at each box. The run of conductor(s) in the conduit may be longer.

Second, a properly-supported vertical run of conduit is unlimited... but only if it is left empty.

As soon as wire is put in it, the maximum length of the run is limited, per 300.19, to 200ft for 6 thru 1/0 AWG AL/CCAL wire.

As worded, "D" would be the best answer, though "All of the above" would have been more appropriate wording. After all, if the vertical conduit run could be 200ft, doesn't that also cover running it 25, 50, and 100 feet???

 

[Smart $]

So you're proving what my teacher taught me:
"if a variable is not defined in an equation...DON'T ASSUME IT".

Why assume conductors if the equation doesn't include said variable?

You said it best:"Second, a properly-supported vertical run of conduit is unlimited... but only if it is left empty. "

Did the question include the wire variable? So why do you assume it?
The question was about "vertical run of conduit", no conductors given, so yes, it's about being an empty conduit.
Trick question? Sure.
Poorly formulated? You answered it.

One, there is no equation in the question.

Two, your teacher likely did not author the question.

Some test questions require assumptions to be made. Most of these types of exams do not offer recourse for explanation or correction of the question. The test taker has to determine the desired answer to get credit, whether that answer is absolutely correct or not.

 

[maghazadeh]

This is the 2nd or 3rd time I find myself to be in agreement with Smart $ in the last cople of days. power to you Mr. Smart $.:thumbsup: