- Location
- New Jersey
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- Journeyman Electrician
So the answer was right in post #7?
Test Ques.
- Thread starter Flight987
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Yea, but screwing with him and his bad attitude was half the fun:lol:
- Location
- Illinois
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- retired electrician
You are really pushing it here. You have been warned a number of times in PMs from moderators. You need to tone it down. People are trying to work with you but you are not making it very easy.
- Location
- Connecticut
- Occupation
- Engineer
I'd say the way the question is written, the answer was right in post #2.
366.23(A) doesn't say anything about the ampacity of the bus bar, just what the maximum allowable current to be carried continuously by a bus bar mounted in an auxiliary gutter.
It seems to me that more than 1050 Amps would be allowed to be carried non-continuously. And even that says nothing about the ampacity of the bus bar.
zog
Senior Member
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- Charlotte, NC
Oh, that makes it OK then I guess.???
jumper
Senior Member
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- 3 Hr 2 Min from Winged Horses
Note to OP. Don does not fool around. On a personal note, quit being rude.
jumper
Senior Member
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- 3 Hr 2 Min from Winged Horses
jumper
Senior Member
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- 3 Hr 2 Min from Winged Horses
http://www.substationsupply.com/images/PDF's/Aluminum Bus Bar Alloy 6101 Ampacity Chart...pdf
1381 amps. Check the temperature ratings
1381 amps. Check the temperature ratings
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- Location
- Illinois
- Occupation
- retired electrician
The OP is looking for an answer for a code test. The only answer that will be acceptable for a code test is the one found in Article 366. While it may not be a technically correct answer to the actual ampacity of the bus, it will be the answer they are looking for in a code test.
Don I don't have the book at this moment so I googled Article 366. I don't see anything but
electrical raceway and gutters. Could you explain how this refers to the question. Maybe I was
looking at the wrong edition.
I just readpost #25. That may be my answer but It does not answer the question of ampacity which is what you said.
electrical raceway and gutters. Could you explain how this refers to the question. Maybe I was
looking at the wrong edition.
I just readpost #25. That may be my answer but It does not answer the question of ampacity which is what you said.
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K8MHZ
Senior Member
- Occupation
- Electrician
K8MHZ
Senior Member
- Occupation
- Electrician
We had questions like that on tests when I was in the apprenticeship. It used to really tick me off. Then, one wise instructor told me something very valuable; when taking multiple choice tests, you aren't looking for the correct answer, you are looking for the best of the offered answers.
- Location
- Lockport, IL
- Occupation
- Retired Electrical Engineer
I would suggest that the one you are looking for is the one that the test author decided would be counted as the correct one. :happyyes:
But then, that probably is not very helpful advice, is it? :happyno:
I sold a lot of switchgear as will as transformers where bus was required and had to interpret specifications. As I recall the bus ampacity had for do with specific standards and temperature rise.
The question can up so infrequently that I had to research it every time that it did as I could never remember the reference.
As such I may have missed it but I didn't see a temperature rise reference noted. I believe that one rating would be based upon a 30degC rise with a 40degC ambient based upon confined air. I believ that the chart that you had posted also included a notation in this regard. You had to go to the link that you had included and page down through the document in order to see it.
But switchboards and panelboards are designed to conform to UL standards, which permit a 55? C rise for switchboards and a 50? C rise for panelboards.
Switchgear conforms to ANSI standard C37.20 Which permits a temperature rise of 65? C above a maximum ambient of 40 ? C, provided that silver-plated (or acceptable alternative) bolted terminations are used. If not a temperature rise of 30? C over the same ambient is allowed.
As such bus ampacity is dependent upon the temperature rise rules that you would be playing by.
The question can up so infrequently that I had to research it every time that it did as I could never remember the reference.
As such I may have missed it but I didn't see a temperature rise reference noted. I believe that one rating would be based upon a 30degC rise with a 40degC ambient based upon confined air. I believ that the chart that you had posted also included a notation in this regard. You had to go to the link that you had included and page down through the document in order to see it.
But switchboards and panelboards are designed to conform to UL standards, which permit a 55? C rise for switchboards and a 50? C rise for panelboards.
Switchgear conforms to ANSI standard C37.20 Which permits a temperature rise of 65? C above a maximum ambient of 40 ? C, provided that silver-plated (or acceptable alternative) bolted terminations are used. If not a temperature rise of 30? C over the same ambient is allowed.
As such bus ampacity is dependent upon the temperature rise rules that you would be playing by.
K8MHZ
Senior Member
- Occupation
- Electrician
Isn't that what I said??? ('decided correct' does not equal 'correct') Or accurate. You only get 4 or 5 choices. If the correct answer is not one of the choices, the best answer is the one that won't get marked wrong.
I think it's great advice. It helps when there is no 'correct' answer. For instance, one of the questions that ticked me off was a question about the minimum bending radius of a conductor. No conductor voltage was given. Just answers like, '4 x the radius', 8 x the radius', etc. There was no choice for 'no minimum'. Rather than get in a tizzy, I knew that the info was somewhere in the book, or the question wouldn't be in the test. Of course, the question was about conductors 600 volts and over, which is where the best answer was found.
Are these 'trick' questions? Trick questions teach nothing, the only affect a person's ego. Or are these simple omissions?
I challenged every question like this during my apprenticeship, even if I got them right. I got some questions changed and for questions that ignored exceptions I got the questions expanded to add the term, 'generally'.
I started doing that in my first year. Now, I admit, I had an unfair advantage. Years earlier, I attended a class targeted at taking the state real estate exam. The exam had a 60 percent failure rate. (Lot's of questions with no 'correct' answers, just best ones) The class I took had an 80 or 90 percent pass rate. I think the biggest reason was that the instructor knew how the tests were written and how they were graded. He also taught us how to take tests, all tests, as it is indeed an art form of sorts. All the students from my class passed the first try. Three hours were allowed for the test, some people still didn't finish. I was out in 45 minutes.
I don't know where that comes from - but, being from across the pond, I don't know a lot about applicable regulations and codes that must be complied with in the US.
A point that occurs to me is that the 700A/in2 doesn't take into account of, among things, the shape of the conductor.
Change the shape of the conductor and the ratio of the perimeter to the cross sectional area changes. The perimeter determines the surface area per unit length of conductor available for cooling. There's a reason (or reasons) why bars are made with unequal height and thickness.
The OP has 6in by 1/4 in. A cross sectional area of 1.5 in2.
The same area in a square bar would be about 1.225 by 1.225 in.
Just out of interest, I did some comparison calcs and the six by quarter can carry 40% more current than the equivalent square bar.
To that extent, I think that the 700A/in2 is a conservative approach to cover all possible configurations and maybe a bit of a blunt instrument.
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