article 250.122 question

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dennis5150

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I am running four 500kcm per phase from a 800KW, 480v, 0.8pf generator (1200A gen breaker) to a switchboard (1200A main), using four 3/c 500kcm (with 3-#6 ground conductors per cable), per phase in ladder botom cable tray. According to 250.122, I need to run four 3/0 EGC's in this tray as well...or am I missing something?
 
dennis5150 said:
I am running four 500kcm per phase from a 800KW, 480v, 0.8pf generator (1200A gen breaker) to a switchboard (1200A main), using four 3/c 500kcm (with 3-#6 ground conductors per cable), per phase in ladder botom cable tray. According to 250.122, I need to run four 3/0 EGC's in this tray as well...or am I missing something?
Click to expand...
I forgot to mention this is MC-HL cable
 
dennis5150 said:
I am running four 500kcm per phase from a 800KW, 480v, 0.8pf generator (1200A gen breaker) to a switchboard (1200A main), using four 3/c 500kcm (with 3-#6 ground conductors per cable), per phase in ladder botom cable tray. According to 250.122, I need to run four 3/0 EGC's in this tray as well...or am I missing something?
Click to expand...

To meet the literal requirement using "cable" the egc at 3/0 would need to be in the cable. If all of the conductors "individual" were in the same cable tray you would need only one 3/0 egc. Paralleled but in one raceway. Parallel raceways,"cables" in your case must contain the egc sized per 250-122. What you propose would work without a doubt. It just would not meet the specific requirement.
 
392.7 may provide some help. If you are using aluminum cable tray and the cross sectional area meets that of table 392.7(B) the cable tray itself could possibly function as the EGC.

Pete
 
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