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Voltage drop.

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jbolen

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I have 75 hp motor on 200 amp breaker due the long distance we install 350 mcm What size grounding conductor should we use in the cable tray.
 
Dsg319

Dsg319

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Location
West Virginia
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Wv Master “lectrician”
jbolen said:
I have 75 hp motor on 200 amp breaker due the long distance we install 350 mcm What size grounding conductor should we use in the cable tray.
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Your EGC is sized per the OCPD and increased proportionally in percentage to the phase conductors.
 
don_resqcapt19

don_resqcapt19

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retired electrician
Assuming a 3 phase 460 volt motor the required conductor size is 2 AWG. That has a cm of 66360, and you used a conductor with a cm of 350,000 so you have increased the wire size by a factor of 5.27. The required EGC from Table 250.122 for a 200 amp OCPD is 6 AWG with a cm of 26,240. The application of the rule in 250.122(B) will require an EGC with a cm of not less than 138, 285, requiring the EGC to be 3/0.
 
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