Conduit fill

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rafca

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I Have this question:
A 1" conduit has 11 conductors, 5 ungrounded, 4 grounded and 2 equipment grounding conductors. The conductors are all AWG 12 THHN stranded at 30C. Assume 60C terminations. If the ambient temperature is 50C, what is the maximum ampacity of the conductor?

a. 20A
b. 15.5A
c. 9.3A
d. 10A

I need help with this question.:happysad:
 
Start with the number of CCC's, since the question does not say the system type we'll need to assume. That assumption puts it at 7, 8 or 9 CCC's, which won't change the answer.

Start with:
T310.15(B)(16) then go to
T310.15(B)(3)(a) then go to
T310.15(B)(2)(a) and let us know what you get.
 
infinity said:
Start with the number of CCC's, since the question does not say the system type we'll need to assume. That assumption puts it at 7, 8 or 9 CCC's, which won't change the answer.
Click to expand...
5 ungrounded and 4 grounded looks to me like one three wire and three two wire circuits, where the grounded conductor in the three wire circuit is not a CCC but the ones in the two wire circuits are. So, 8 CCC's.

But, as you point out, whether it's 7,8, or 9 doesn't change the answer, so the time I would have spent figuring that out would have been wasted. Test writers have very devious minds. :D
 
ggunn said:
5 ungrounded and 4 grounded looks to me like one three wire and three two wire circuits, where the grounded conductor in the three wire circuit is not a CCC but the ones in the two wire circuits are. So, 8 CCC's.

But, as you point out, whether it's 7,8, or 9 doesn't change the answer, so the time I would have spent figuring that out would have been wasted. Test writers have very devious minds. :D
Click to expand...

You're making an educated guess but without knowing the system type you cannot determine if it's 7, 8 or 9 CCC's. In your example if this were a 208Y/120 volt system or a 480Y/277 volt system you would have 9 CCC's not 8.
 
infinity said:
You're making an educated guess but without knowing the system type you cannot determine if it's 7, 8 or 9 CCC's. In your example if this were a 208Y/120 volt system or a 480Y/277 volt system you would have 9 CCC's not 8.
Click to expand...
What if :)p) two of the grounded conductors are spares?

You may only have 6 CCC's... one full boat (4-wire but 3 CCC), one 3-wire (3 CCC), 2 spare (0 CCC), 2 EGC (0 CCC). The question is what is the maximum ampacity, and 6 CCC's would yield the maximum.
 
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Smart $ said:
What if :)p) two of the grounded conductors are spares?

You may only have 6 CCC's... one full boat (4-wire but 3 CCC), one 3-wire (3 CCC), 2 spare (0 CCC), 2 EGC (0 CCC). The question is what is the maximum ampacity, and 6 CCC's would yield the maximum.
Click to expand...
Lets use the 2014 code then...you have to count the spares as current carrying conductors.
 
Smart $ said:
What if :)p) two of the grounded conductors are spares?

You may only have 6 CCC's... one full boat (4-wire but 3 CCC), one 3-wire (3 CCC), 2 spare (0 CCC), 2 EGC (0 CCC). The question is what is the maximum ampacity, and 6 CCC's would yield the maximum.
Click to expand...

What if they're all spares, how would you know if any are spares based on the question?
 
Yes, but I think that we can agree that the creator of the question probably had no such thought.

At a certain point these hypotheticals, things that go well beyond the wording of the question, just obfuscate the original intent of the question and confuse the poster seeking an answer.
 
infinity said:
Start with the number of CCC's, since the question does not say the system type we'll need to assume. That assumption puts it at 7, 8 or 9 CCC's, which won't change the answer.

Start with:
T310.15(B)(16) then go to 20 A
T310.15(B)(3)(a) then go to .70
T310.15(B)(2)(a) and let us know what you get. .58
Click to expand...

rafca said:
I Have this question:
A 1" conduit has 11 conductors, 5 ungrounded, 4 grounded and 2 equipment grounding conductors. The conductors are all AWG 12 THHN stranded at 30C. Assume 60C terminations. If the ambient temperature is 50C, what is the maximum ampacity of the conductor?

a. 20A
b. 15.5A
c. 9.3A
d. 10A

I need help with this question.:happysad:
Click to expand...


20 x .7 x.58 = none of the above

however if we somehow assume 6 or fewer CCC, we can use .8 instead of .7 and we get 9.3 which is one of the answers.

I think this is the correct answer since it asks for the maximum ampacity and clearly the only way to get that is to assume 6 or fewer CCC which is possible given the test question. And, the number I came up with actually matches one of the possible answers given.
 
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petersonra said:
20 x .7 x.58 = none of the above

however if we somehow assume 6 or fewer CCC, we can use .8 instead of .7 and we get 9.3 which is one of the answers.

I think this is the correct answer since it asks for the maximum ampacity and clearly the only way to get that is to assume 6 or fewer CCC which is possible given the test question. And, the number I came up with actually matches one of the possible answers given.
Click to expand...


Given the question in the OP how could you come up with 6 CCC's?
 
infinity said:
Given the question in the OP how could you come up with 6 CCC's?
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The five ungrounded consist of two 120/240 MWBC's. That gives us four CCCs and uses up two of the grounded conductors. The fifth ungrounded forms a single circuit using one of the remaining grounded conductors. Both of those count. Total = six.
The fourth grounded conductor is a spare, there just to satisfy the neutral requirement for a hypothetical device which may be installed in a switch box at a later time, and is not connected to any outlet of any kind. (Or does its mere presence inside a switch box make it "utlilized"?)
 
petersonra said:
20 x .7 x.58 = none of the above

however if we somehow assume 6 or fewer CCC, we can use .8 instead of .7 and we get 9.3 which is one of the answers.

I think this is the correct answer since it asks for the maximum ampacity and clearly the only way to get that is to assume 6 or fewer CCC which is possible given the test question. And, the number I came up with actually matches one of the possible answers given.
Click to expand...

infinity said:
Given the question in the OP how could you come up with 6 CCC's?
Click to expand...

I think a better question would be given the question in the OP, how did you come up with 20 and 0.58? The OP states THHN, it should be 30 and 0.82
 
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