Current carrying conductor question

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sceepe

sceepe

Senior Member
The following is from Mike Holt's newletter email dated 7/9/4:

Q 2. If I am using four 500 THHN kcmil conductors in each raceway (all current carrying), how many parallel runs would be required for a 2000A feeder?

A 2. The installation of four current carrying conductors in a raceway requires the use of an ampacity adjustment factor of 80% per Table 310.15(B)(2)(a). The 90?C ampacity of 500 kcmil copper is 430 amperes. The adjusted ampacity for 500 THHN is 430A x 0.80 = 344A. This installation will require the use of six sets of 500kcmil for a 2000A circuit (2,000A/344A).
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Am I missing something here? Why would you have 4 current carrying conductors for a 2000A feeder. Only thing I can think of is the non-linear load issue mentioned in 310.15.B.4.c.
 
Re: Current carrying conductor question

I would say that this is not intended to describe a real installation. It is merely an exercise in reading the code. By having stated that there are four current-carrying conductors, the person who wrote the question is calling upon the reader to bring Table 310.15(B)(2)(a) into the party.
 
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