Originally Posted By: dbush This post was automatically imported from our archived forum.
Okay, I promised an electrical topic, here we go. The topic will be electric all week as several people have requested. If anyone has a request for a topic next week just e-mail or pm me.
Originally Posted By: jfarsetta This post was automatically imported from our archived forum.
I suspect I know the correct answer, though I did not choose it. The panel being rated at 150 amps is the red herring. So long as the voltage and amperage does not exceed the panel rating, you’re okay.
The relation of the #6 copper to the 100A main breaker is the key. I'm assuming the #6 is the size of the service entry cable. Is that correct Dave?
-- Joe Farsetta
Illigitimi Non Carborundum
"Dont let the bastards grind you down..."
Originally Posted By: dvalley This post was automatically imported from our archived forum.
A #6 copper SE wire will have a tendancy to melt in this situation (if an overload occurs), causing a fire. The 100 amp breaker is waiting for 100 amps of surge before it will trip. Not gonna happen with a #6 copper wire. This #6 wire will only give that 100 amp breaker a max of 60 amps of electricity.
Originally Posted By: Bob Badger This post was automatically imported from our archived forum.
Blaine, no brain cramp you are correct.
310.16
8 AWG @ 60 C = 55 amps
8 AWG @ 75 C = 65 amps
Most modern equipment (panel, breaker, meter terminals) will be marked as 75 C allowing the use of the 75 C amp rating.
If all the terminals involved are not marked as 75 C then you would have to use the 60 C rating, assuming 75 C or 90 C insulation. 110.14
My guess is the old cloth covered stuff along with TW is 60 C insulation.
But 240.4(B) could allow the use of the next size standard breaker for this application.
It would be tough to check for the terminal ratings during a home inspection, but considering 240.4(B) the use of 6 AWG on a 60 amp breaker would not seem strange to me.
Originally Posted By: gbeaumont This post was automatically imported from our archived forum.
Hi Jeff,
within the terms of the question, it should be noted that it is in fact a 60 amp supply due to the rating of the conductor, therefore the fact that it has a 100 amp main disconnect is somewhat an extra.
this question is very typical of those questions used on NHIE and other licensing exams, quite often the question or answers seem somewhat ambiguous, but there is actually only one answer that can be totaly correct given the options available in this question 60 amp is the only correct answer.
But I must admit, the discussion is as useful as the questions 
Originally Posted By: roconnor This post was automatically imported from our archived forum.
Hmmmmm … well lets see now.
If it's one set of #6 Cu service feeders (3-#6) then the conductors would limit the service capacity to 60A.
If its two sets of #6 Cu (6-#6) service feeders (parallel conductors), then the MD would limit the service capacity to 100A.
It could be taken that it's a standard 3-wire service, since there is no mention of parallel conductors and current model codes would usually limit parallel conductors to #1/0 and larger. Then again current codes would not allow anything less than a 100A service with #4 Cu for a typical residence ... 
[Okay, thats a stretch ... but Dave gave away the "correct" answer ... ]
-- Robert O'Connor, PE
Eagle Engineering ?
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I am absolutely amazed sometimes by how much thought goes into doing things wrong