proper sizing for 1200 amp service switchgear

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mgelectric

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have a project that will take a 1200 amp switchgear would like to know the
proper steps to determine how to calculate the conductor size for parallel
run. conductor are in buried conduit. thanks for anyones help. mg
 
mgelectric said:
How did you come to that info. More detail please. Thanks
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scary !

I was assuming (bad) that you are spekaing of gear with a 1200 amp main, in which case the ampacity of your condcutors must be at least 1200 amps. Most gear is 75 deg rated, therefore it's 1200 amps per 75 deg column. Bob's method would be 1260 amps (assuming normal ambient), mine would be 1240 amps.
(again assuming parallel runs in seperate conduits)
Depending on how many conduits you wish to run you could install anything from (2) runs of 1250kcmil to (8) runs of 1/0.
(all copper)

If you are speaking of gear without a main, then you could go with conductor ampacity equal to or greater than the calculated load.
 
:cool:
Agree with Iwire...did inspection on one today...3x600Cu.

Math...420 amps per 600Cu.....times 3 sets....1260 amps.....1200 amp main cb or fuses.

2005 NEC compliance

Augie:
Don't mean to rain on your parade....ya type faster then me!
 
mgelectric said:
How did you come to that info. More detail please. Thanks
Click to expand...



240.4(C) - 110.14(C) - and Table 310.16 75?C column.
Reading these parts of the code gives you your answer.

You do have to make sure the equipment comes with the proper size, and number of termination points for the wire you're going to use.
 
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