Conduit fill

[rafca]

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:

 

[infinity]

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.

 

[George Stolz]

And for the record, it's not a pipe fill question, it's an ampacity question.

 

[don_resqcapt19]

More information is needed to answer the question.

I am wrong...there is enough information

 

[rafca]

More information is needed to answer the question.

I am wrong...there is enough information

Thank you for the help, I get my answer.
9.3A

 

[infinity]

Can you share your calculation for others who may want to follow along?

 

[don_resqcapt19]

Thank you for the help, I get my answer.
9.3A

Do you want to show your work?

 

[ggunn]

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.

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.

 

[infinity]

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.

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.

 

[Smart $]

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.

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.

 

[don_resqcapt19]

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.

Lets use the 2014 code then...you have to count the spares as current carrying conductors.

 

[Smart $]

Lets use the 2014 code then...you have to count the spares as current carrying conductors.

So you are aware of a jurisdiction adopting the 2014 edition... before 2014???

 

[infinity]

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.

What if they're all spares, how would you know if any are spares based on the question?

 

[Smart $]

What if they're all spares, how would you know if any are spares based on the question?

That's a valid point... if they were all spares, there would still be a maximum ampacity though, correct?

 

[infinity]

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.

 

[petersonra]

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

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:

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.

 

[infinity]

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.

Given the question in the OP how could you come up with 6 CCC's?

 

[petersonra]

Given the question in the OP how could you come up with 6 CCC's?

It was the only way to get one of the answers allowed.

Therefore, there must be 6 or fewer CCC.

 

[GoldDigger]

Given the question in the OP how could you come up with 6 CCC's?

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"?)

 

[david luchini]

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.

Given the question in the OP how could you come up with 6 CCC's?

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