trick question?

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tryin

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Quiz question from electrical practice test.

5 number 4 awg non-leaded conducters in a concealed location in an existing conduit will need to be de rated at?
The chart for 4-6 conductors (310-15) must not apply because there is not a choice for the 80% as shown in the table on the list of choices on the test.. Would this automatcialy fall under 40% rule for conduit detrating or not?
 
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tryin said:
Quiz question from electrical practice test.

5 number 4 awg non-leaded conducters in a concealed location in an existing conduit will need to be de rated at?
The chart for 4-6 conductors (310-15) must not apply because there is not a choice for the 80% as shown in the table on the list of choices on the test.. Would this automatcialy fall under 40% rule for conduit detrating or not?
Click to expand...

What are the 5 wires? Are they all current carrying conductors?
 
First of all the question is horribly written. Secondly it could be interpreted that no derating is required if the conduit contains
A, B, C, N, EGC.
 
What is this so-called automatic 40% rule?

Are you referring to the 40% rule for raceway fill?

If this is an actual practice test question, I'd ditch the whole book. If this in an example from that book, who know what other horrible, poorly-written questions are there that will lead you the wrong way.
 
Thats all they are giving me, the answers are 40%,25%,53.1% ,70%
They didn't say the size of the conduit, only the conductors and they said they were non leaded, 0% is not a choice. I keep thinking that as a rule of thumb, Gutters /troughs are 20% conduit fill is 40%,nipples are 60%. I guess because they never gave me anymore information than that I used the standard one which is 40%. Is it a concealed space question? a de rating question or what the heck. I used the 310.15 chart and 80% is not an option.
 
tryin, derating applies to the ampacity of the conductors, not to the size of

a conduit or gutter. If these wires were in a 2" conduit or a 4" conduit they

would have to be derated the same way. Does that help??
 
Never mind, The conduit also has 3 # 6 conductors in it, existing. So I added them together and chose the 7-9 and the derating factor 0f 70%. I hope I'm not missing something because it's in a concealed space, sometimes the way they word these things makes me second guess myself.
 
tryin said:
Never mind, The conduit also has 3 # 6 conductors in it, existing. So I added them together and chose the 7-9 and the derating factor 0f 70%. I hope I'm not missing something because it's in a concealed space, sometimes the way they word these things makes me second guess myself.
Click to expand...

Concealed space, non-leaded conductors, existing conduit, all are smokescreens. They're extaneous words thrown in to throw you off track. Kind of like custom home. It's still just a dwelling as far as the NEC is concerned. Delete the words that have nothing to do with the Code. The question is simply asking what % of derating is needed for 8 conductors in a raceway. No neutral is stated, so you can't deduct any from your conductor count. It's not stated to be a nipple. So, what number is next to the 8 in T310.15(B)(2)(a)? 70%. You were correct! :smile:
 
cowboyjwc said:
When you are giving a test, I just don't think that it's necessary to muddy up the question with a bunch of nonsense information.
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It's intentional on the part of the test writers.

Think about it. They are in the business of administering tests. They charge you money to take their test. Once you pass the test, you are no longer a potential customer. So they have a vested interest in you failing the test.

In order to do that, they throw extraneous information into a question to slow you down. They also throw in double-negatives to trick you. Instead of a dwelling, they'll call it a custom home. They'll send you on wild goose chases (look up Electric Welders in the index for an example).


Two test questions that I really remember that stood out to me:

Q1. A feeder is shown in a diagram for three motors, a 5HP 3ph, a 15HP 3ph, and a 50HP 3ph. Calculate the minimum feeder size.

Now you flip the page, and there's the same diagram:

Q2. A feeder is shown in a diagram for three motors, a 5HP 1ph, a 15HP 3ph, and a 50HP 3ph. But this diagram has 21Kw of lighting on it, too. Now, calculate the minimum feeder size.

Did anyone notice the two differences in the two questions?
 
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