Naveen Kumar
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- Teaxas, USA
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- Student
What is the condition of use (COU) ampacity of 8 #10 CU THWN-2 conductors installed in one conduit at ambient temperature of 35°C?
Test question
- Thread starter Naveen Kumar
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- Bremerton, Washington
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We won’t give you the answer. Where have you looked?
Naveen Kumar
Member
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- Teaxas, USA
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- Student
Naveen Kumar
Member
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- Teaxas, USA
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- Student
Also desciption says "Not More Than Three Current-Carrying Conductors in Raceway,"
but my question have 8#10, can we use that NEC? or the quesstion is wrong?
but my question have 8#10, can we use that NEC? or the quesstion is wrong?
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- New Jersey
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- Journeyman Electrician
The question is wrong because it does not tell you the number of current carrying conductors. And what is condition of use (COU)?
LarryFine
Master Electrician Electric Contractor Richmond VA
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- Henrico County, VA
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- Electrical Contractor
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- New Jersey
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- Journeyman Electrician
It says 8 conductors not 8 CCC's. It could be 6 CCC's which is a different derating percent than 8 CCC's.
LarryFine
Master Electrician Electric Contractor Richmond VA
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You're right, of course. My bad.
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- Chapel Hill, NC
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I would work with 8 current carrying conductor's using T310.16, T310.15(B)(1) and T310.15(C)(1)
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- New Jersey
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Probably the intent but the question is poorly written.
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- Chapel Hill, NC
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Absolutely but he may as well figure that way as there is no other way to do it other than configuring it many ways
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- New Jersey
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- Journeyman Electrician
If this were a multiple choice question to could solve it for every possible scenario and then see if only one of the answers is in the list of choices. If more than one answer is available then the question is unanswerable. Since no list of answers was given I would assume that this is not a multiple choice question.
Tulsa Electrician
Senior Member
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- Tulsa
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- Electrician
Hope the OP showes is his math. Then we can help him with what CCC he uses. At least he will know how to do for when a good question come up.
Entry level question I would use 8.
Mid level and upper level question related prior to that question. Identify the CCC then calculate.
Entry level question I would use 8.
Mid level and upper level question related prior to that question. Identify the CCC then calculate.
Naveen Kumar
Member
- Location
- Teaxas, USA
- Occupation
- Student
Hi, Thanks for replying guys.
My assumption, for now, is 8 CCC,
Also just neglecting the term "Condition of use". I have no idea about it. Give me suggestions if anyone knows
According to Table 310.16(Cu-THWN2-#10) ampacity is 40
but it has more than 3CCC, so according to "Table 310.15(B)(3)(a)" 8ccc 70% of 40 = 28
Also, ambient temp is 35, so according to 310.15(B)(2)(a) , correction factor is 0.96 of 28 = 26.88
So the breaker should be 30A
My assumption, for now, is 8 CCC,
Also just neglecting the term "Condition of use". I have no idea about it. Give me suggestions if anyone knows
According to Table 310.16(Cu-THWN2-#10) ampacity is 40
but it has more than 3CCC, so according to "Table 310.15(B)(3)(a)" 8ccc 70% of 40 = 28
Also, ambient temp is 35, so according to 310.15(B)(2)(a) , correction factor is 0.96 of 28 = 26.88
So the breaker should be 30A
Carultch
Senior Member
- Location
- Massachusetts
Conditions of use, is a collective way to refer to the conditions that cause the ampacity to be less than the values in Table 310.15(B)(16). Condition 1 is an ambient temperature (or air temperature with an applicable temperature adder) other than the table's reference temperature of 30C, and condition 2 is that you have more than 3 conductors in a raceway, which limits their ability to disperse their heat to the surroundings. These two conditions are collectively called "conditions of use". Both factors that are associated with each condition, will multiply to compound with each other.
At one point, both factors were called derate factors, and you'll still hear people use this name. Now they are called temperature correction and ampacity adjustment factors.
Naveen Kumar
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- Teaxas, USA
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- Student
Tulsa Electrician
Senior Member
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- Tulsa
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- Electrician
"The breaker should be 30" is questionable.
What you have done is determine that allowable ampicicty of the conductor based on the conditions you used for derating.
Something to keep in mind. The conductor has to carry the load.
So the code may allow you to use the 30 breaker is some cases and not in others. For that you will need to consider over current protection or artical 240 for guidance. Then apply the correct code section to see if a 30 breaker is ok.
Granted not part of your question. Just a response to you ansawer given.
Thank you for providing your answer to the question so we could help.
What you have done is determine that allowable ampicicty of the conductor based on the conditions you used for derating.
Something to keep in mind. The conductor has to carry the load.
So the code may allow you to use the 30 breaker is some cases and not in others. For that you will need to consider over current protection or artical 240 for guidance. Then apply the correct code section to see if a 30 breaker is ok.
Granted not part of your question. Just a response to you ansawer given.
Thank you for providing your answer to the question so we could help.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
- Location
- New Jersey
- Occupation
- Journeyman Electrician
I agree. Don't read information into the question that doesn't exist. They asked for the ampacity which is 26.8 amps a 30 amp OCPD may be too large.
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