Question on Exam taken this week (correction)

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mnrhudson

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Soon to live in Surf City N.C.
Okay the question read : An office building is needing some 120v. receptacles run and is being feed by a #2 thw copper feeder, what would the overcurrent device be on this feeder?
Don't remember the 4 possible answers. Made a 72 on test and it was at the end i got the question over 5 and a half ours later...:confused:
 
infinity

infinity

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IMO the question is unanswerable in it's present form since there is too much information missing.
 
westernexplorer

westernexplorer

Senior Member
Based on the information you have given, please dont take this personal, I feel you have left out or don't remember the exact wording of the question.....believe me I have been there, and taken many exams. I will try and help you with the sizing of OCP for this feeder.....

1. #2 THW Copper by 310.16 @75 degrees is good for 115 Amps
2. Receptacles are not calculated as continous, so a feeder to a sub-panel for receptacle loads could be based on the ampacity of your wire size.
3. A 110 amp breaker to protect this feeder would be the maximum OCP device for this feeder, since 240.4 (B) would prohibit you from jumping up to the next standard size OCP device.

Ofcourse a smaller OCP device could be used as long as the calculated or connected load did not exceed that of the Feeder OCP device....


I hope this helps.....
 
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nakulak

Senior Member
why would 240.4 B prohibit 125 amps ? this is a feeder, not part of a mult outlet branch ckt.


as such, though, it still doesn't add up. i come up with the following:

220.14 I

180VA x 120= 21600

21600/120v = 180 Amps

demand
220.44

10kva + .5 x 11600 =15800


15800/120v= 132 amps calculated load


#2 THW = 115 amps (310.16)
next size up 125 Amps (240.4 B)

hmmmm . . .
 
westernexplorer

westernexplorer

Senior Member
Nakulak,

Your right about 240.4(B) I got ahead of myself.....that would be for a BRANCH CIRCUITS not a feeder........ either way a 110 or 125 amp would be the maximum OCP for this wire, if the question was worded like the OP states.......some how I think we are missing some information........
 
westernexplorer

westernexplorer

Senior Member
And ofcourse it would all depend on the awnsers that the OP had to choose from on the exam.....

If 125 amp was a choose I would have went with that, unless the awnser jumped from 110 amp to 150 amp and then I would have taken 110 amps......

In any case we don't have all the information.....But we can quess......LOL....
 
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mnrhudson

Member
Location
Soon to live in Surf City N.C.
No, the test was the limited in N.C. the question gave no information at all other than a office feeder for 120v recepatcles and it was going on a #2 THW wire and wanted me to size the overcurrent, that was really all the info it gave. My insturctor told me due to it being in an office building I should have taken the 115amps on the #2 x 125% . I don't remember the answers but i made a 72 on the test (HEART BREAKER) Huh?
But thanks for asking,
mnrhudson
 
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mnrhudson

Member
Location
Soon to live in Surf City N.C.
The test qsuestion was the limited in N.C. the question gave no information at all other than a office feeder for 120v recepatcles and it was going on a #2 THW wire and wanted me to size the overcurrent, that was really all the info it gave. My insturctor told me due to it being in an office building I should have taken the 115amps on the #2 THW wire and x it by 125% . I don't remember the answers
 
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mnrhudson

Member
Location
Soon to live in Surf City N.C.
The test question was the limited in N.C. the question gave no information at all other than a office feeder for 120v recepatcles and it was going on a #2 THW wire and wanted me to size the overcurrent, and that was really all the info it gave. My insturctor told me due to it being in an office building I should have taken the 115amps on the #2 x 125% . I don't remember the answers.
mnrhudson
 
westernexplorer

westernexplorer

Senior Member
Generally receptacles are not calculated as continous whether in a dwelling or commercial occupancy....... Unless the question stated continous loads........
 
R

realolman

Senior Member
The size of the OCPD on the feeder would have nothing to do with receptacles. It should have to do with the size of the feeder ...

The size of the feeder might have something to do with the receptacles.

I'd say something's missing or befuddled.
 
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