De-rating conductors

[02harleyfxdl]

A SET OF PLANS THAT HAS 4- 3/0 CONDUCTORS WITH A #6 GROUND IN RMC. LENGTH IS > 10 FT AND IT SUPPLYS FOUR ATTACHED STRIP MALL UNITS. 200 AMP SERVICE AT EADCH UNIN IN RMC THAT WILL BE BURRIED. HE STATES THAT SINCE IT'S 3 PHASE IT DOESN'T HAVE TO BE DE-RATED.

 

[raider1]

Welcome to the forum.

If you are asking about adjusting the ampacity for more than 3 current carrying conductors in a raceway you need to look at 310.15(B)(4) for when a neutral conductor counts as a current carrying conductor in regards to the ampacity adjustments in 310.15(B)(2)(a).

Most likely the neutral will not count as a current carrying conductor.

Chris

 

[charlie b]

I am concerned that you have a feeder rated for 200 amps, and you are serving four separate 200 amp loads. Is there a load calculation that shows the total to be under 200 amps?

Welcome to the forum.

By the way, please turn off the ALL CAPS feature on your keyboard. It makes the text harder to read, and is considered impolite (as though you were SHOUTING at us).

 

[poeboy]

if your using copper conductors, at least 75 degree rated, then chances are good that only the 3 hots count towards the derating max. If, however they are aluminum, and 60 degree rated, they will not come close enough to 200 A to use a 200A breaker.

Use the table mentioned above to find your answer.