Trouble with Mike Holts understanding the nec vol 1 question.

[haakefan]

I'm practicing up on my 2014 code book by looking through and doing mike holts questions when I got stumped on article 404 question 5;


"A multipole, general-use snap switch shall not be fed from
more than a single circuit unless it is listed and marked as
a 2-circuit or 3-circuit switch, or unless its voltage rating is
not less than the nominal _____ voltage of the system supplying the circuits."

a. line to ground
b. line to neutral
c. line to line
d phase to phase

Not that I'm looking for the answer exactly. But where in the code book can i find this answer? I thought that 404.14(rating and use of snap switches) would be where to go but I found no definitive help there.

 

[mgookin]

I'm practicing up on my 2014 code book by looking through and doing mike holts questions when I got stumped on article 404 question 5;


"A multipole, general-use snap switch shall not be fed from
more than a single circuit unless it is listed and marked as
a 2-circuit or 3-circuit switch, or unless its voltage rating is
not less than the nominal _____ voltage of the system supplying the circuits."

a. line to ground
b. line to neutral
c. line to line
d phase to phase

Not that I'm looking for the answer exactly. But where in the code book can i find this answer? I thought that 404.14(rating and use of snap switches) would be where to go but I found no definitive help there.

I think it's a good question and I think it's trying to get you to think. That's the best education you can get.

So what is the concern in the question?

And what is the worst thing that could go wrong?

 

[don_resqcapt19]

What edition of the code book are the questions based on?

That question is not valid for the 2014 code, but was valid for the 2008 and 2011 codes as far as the NEC goes. However the code for the 2008 and 2011 editions was at odds with the product standard that covers switches. The wording in the 2014 code matches the product standard.

The answer is in Article 404 and occurs prior to the section you cited.

 

[charlie b]

Am I the only one who has a problem with the wording of this test question? For almost all the work we do, answers A and B are the same, and answers C and D are the same. Or do I need more coffee? :?

 

[mgookin]

Am I the only one who has a problem with the wording of this test question? For almost all the work we do, answers A and B are the same, and answers C and D are the same. Or do I need more coffee? :?

I'll send you a pm because I don't want to give away (what I think to be) the answer to the OP.

Edit - Never mind: I got tripped up. Let's get the OP back on here and see how he's handling it.

 

[GoldDigger]

Am I the only one who has a problem with the wording of this test question? For almost all the work we do, answers A and B are the same, and answers C and D are the same. Or do I need more coffee? :?

The "phase to phase" phrase just does not make sense. The line to line voltage is normally considered to be the phase voltage.
Line to neutral and line to ground are not necessarily the same for ungrounded systems or systems without a neutral.

 

[ActionDave]

Am I the only one who has a problem with the wording of this test question? For almost all the work we do, answers A and B are the same, and answers C and D are the same. Or do I need more coffee? :?

I think the point of the question is to find the code section and see what word is used to determine the answer.

You could make the distinction between A and B that a neutral is not the same as ground until it gets bonded. C and D are the same to me.

 

[Dennis Alwon]

The answer is in the 2011 NEC as Don stated and almost word for word.

 

[charlie b]

The "phase to phase" phrase just does not make sense. The line to line voltage is normally considered to be the phase voltage.

I have seen all three sets of words (i.e., "phase-to-phase voltage," "phase voltage," and "line-to-line voltage") used to convey the same concept. I don't have a problem with either of them. I do have a problem with using two of them as possible answers to a test question, with the expectation that one answer is right and the other is wrong. I realize that the 2011 NEC uses one, and only one of these phrases in the relevant article. That does not make for a good test question, however.

Line to neutral and line to ground are not necessarily the same for ungrounded systems or systems without a neutral.

That is why I said "for almost all the work we do."

 

[jumper]

One reason IMO phase to phase is incorrect, because if you a 2 circuit switch on a 120/240V system and the circuits were on opposite legs/poles you would have only L-L as a voltage reference between the two poles/legs on the switch as a maximum.

Line to Line satisfies both 1 phase and 3 phase systems for the question. Phase to Phase does not.

".....its voltage rating is
not less than the nominal _____ voltage of the system supplying the circuits"

 

[don_resqcapt19]

Am I the only one who has a problem with the wording of this test question? For almost all the work we do, answers A and B are the same, and answers C and D are the same. Or do I need more coffee? :?

While they mean the same thing, the question is looking for the specific wording found in the code section.

 

[don_resqcapt19]

The answer is in the 2011 NEC as Don stated and almost word for word.

But even if you are still on the 2011 code, you can't use a switch on two circuits unless is it specifically listed for use with more than one circuit, no matter what the voltage rating of the switch is. This was just poor code as the code and the listing instructions were in conflict.

And even if you have a switch listed for multiple circuits you still have the issue of the code requiring a common means of disconnect for both circuits on the line side of the switch.

 

[haakefan]

Ive been mulling over the question for the past couple of days and took my head out of the book to only think critically. Since were talking about multi circuits i can only surmise that the switch would need to be rated for line to line voltages. Is that correct?

(Sent this as an email response to a mod not realizing that the form was up)

 

[jumper]

Ive been mulling over the question for the past couple of days and took my head out of the book to only think critically. Since were talking about multi circuits i can only surmise that the switch would need to be rated for line to line voltages. Is that correct?

(Sent this as an email response to a mod not realizing that the form was up)

Line to Line is correct as that was the exact wording in the NEC in previous editions.

In 2014 the wording is different, Don stated this in an earlier post.