GEC Size ?

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RooKie12

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I have a parallel service feed with the largest ungrounded conductor size of 4/0. My waterground size would be #4 CU ? I dont really grasp what the

or
Equivalent Area for Parallel
Conductorsa (AWG/kcmil) means?
 
Are you saying that you have a set of parallel conductors with each conductor of the paralled set being a 4/0?

Chris
 
So let me get this straight,

You have 2 parallel 4/0's for each ungrounded phase and 2 parallel 2/0's for the grounded (neutral) conductor correct.

If that is the case then to get the total area of the largest ungrounded paralleled conductor you would need to get the area in circular mils of a 4/0 for Table 8 Chapter 9 and multiply that by the number of sets of paralleled conductors. In this case 4/0 has an area in circular mils of 211600 circular mils. If you times 211600 by 2 then you get a total area of 423200 circular mils. This would equate to just below a 500 kcmil conductor.

So going back to Table 250.66 you would have an ungrounded conductor size of over 350 though 600 (assumming copper) and would need a GEC sized at 1/0 copper.

Chris
 
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Actually the feeder conductors are aluminum 4/0 so it would be 2awg cu or a 1/0 Alu needed for the waterground.
 
Thanks for the welcome and I'm an electrical inspector just had a brain freeze on this one for some reason lol . This certain job had a #4 cu for a 400A paralleled service and i knew it was wrong just figured I'd make sure before I contacted him to fix it. To many beers last night
 
You may have to change your subscript..."I thought I made a mistake once but I was wrong"..vs.."I thought I made a mistake once and I was right"...I often have to count my mistakes using front-end estimation, single digits are just too slow...
 
highendtron said:
You may have to change your subscript..."I thought I made a mistake once but I was wrong"..vs.."I thought I made a mistake once and I was right"...I often have to count my mistakes using front-end estimation, single digits are just too slow...
Click to expand...

Memory doesn't count against ya lol
 
hillbilly said:
4/0 parallel Aluminum to feed a 400A service?

Where's my book?

steve
Click to expand...

Paralleled 4/0 aluminum conductors at 75 degrees C have an ampacity of 360 amps. Provided that the calculated load does not exceed that you can use the next size up rule in 240.4(B) and protect the conductors with a 400 amp breaker.

Chris
 
raider1 said:
Paralleled 4/0 aluminum conductors at 75 degrees C have an ampacity of 360 amps. Provided that the calculated load does not exceed that you can use the next size up rule in 240.4(B) and protect the conductors with a 400 amp breaker.

Chris
Click to expand...

True, but if I'm paying for a 400 amp service I want 400 amps worth of conductors. Never know if you may need some more juice in the future. :rolleyes:
 
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