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Joined: Dec 2000
Posts: 4,294
Member
I'll throw in with the others and call it "B", for the exact reasons stated (could be TW, and it's #1 or smaller, either of which qualify)
60°C

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Joined: Oct 2000
Posts: 2,749
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B., should be considered as the correct answer, see Section 110-14(c)(1) in the 1999 NEC.

[This message has been edited by Joe Tedesco (edited 11-21-2001).]


Joe Tedesco, NEC Consultant
Joined: Oct 2001
Posts: 172
W
Member
When I first read the question I choose B as the answer. I think that 110-14 (c)(1)(b)would confirm this answer as the correct one. I also read 110-14 after the apparant confusion in some of the posts on this one. While I still think B is the answer to the test question, I am really confused by this sentence in 110-14(c). Conductors with temperature ratings higher than specified for terminations shall be permitted to be used for ampacity adjustment, correction, or both. What's up with this? This seems to be totally opposite of the termination rules. I thought ampacity adjustments were made by increasing conductor size not temperature ratings of the conductor. Could some of you sparkys shed some light on this.
(pun intended)

watthead

Joined: May 2001
Posts: 176
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Member
I will agree with the (b) answer.
To answer WattHead's question. As I understand the NEC, there are two derating applications for a conductor. The first is for temperature. Lets assume you have a 75 deg. THHN #6 conductor that passes through a higher than normal temperature area, say 60 Degree C ambient (140F), the typical attic temperature in the summer time. You have to derate the ampacity from the 75 amps by using the multiplier at bottom of Table 310-16. That is 75 X 0.71=53.25Amps. Secondly, lets say you have 4 of those conductors in a conduit. According to Table 310-15(b), the adjustment factor is 80%. That is 53.25 X .8= 42.6 Amps. The termination temperature is still a 60 degree termination.
If you start with a different conductor insulation, such as TW or UF, then the beginning ampacity is at 55 amps for the same #6 conductor. Therefore, if we apply the same multipliers, the final conductor ampacity will be: 55 X .71 X .8= 31.24 amps.
That's how I understand it.

Joined: Oct 2000
Posts: 4,116
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atran,

Looks like it's just me 'n you on the "C" answer. Even though we're in the minority here I still think we got the 'right' one! [Linked Image]

Let me take one more stab at my justification here ..

(b) It is required to be terminated at 60 degree C ampacity - not necessarily, .. right?

(c) It must have insulation rated 60 degree C ampacity. - yes, it must have insulation rated for at least 60C. (nothing lower in the table)

I'm done.
[Linked Image]
Bill


Bill
Joined: Apr 2001
Posts: 449
F
Member
Bill, I chose "C" as well for the same reason, if it was rated less than 60ºC you couldn't terminate it at all could you? I considered "B" as a trick answer.

Joined: Sep 2001
Posts: 3
T
Junior Member
Whenever I have come across a question of this type in the past, I would use the basic rule and make a note at the end of the exam. In this note, you would explain that you feel the question is misleading or lacking information and explain why you gave the answer that you did. It is possible that you could still earn some credit if the answer is wrong.

Joined: Sep 2001
Posts: 19
D
Member
"C" is more correct than "b" also in our State Journeymans/Masters tests we have an option to review our test. This means we may setup a time with the state inspection dept. to go over our answers to the questions. According to most state inspectors here there may be a few questions on the test with a.wrong, b.mostly wrong, c.partly wrong, d.right. If in a review an applicant can give a good argument as to why he or she answered a c.partly wrong question the board would give the question approval. These are only on an individual bases so 10 people could choose this anwer and only one get it correct due to their reply on the answer.


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