NEC 250.122 and Table 250.122

[deee]

I am asked to size an Aluminum equipment grounding conductor for four 3 phase motors that is supplied by one set of 2/0 conductors protected by 150 amp circuit breaker. I am allowed to use Table 220.122 but there is no allocation for a 150 amp circuit breaker. I guess that if there is no reference for 125 amps and 150 amp circuit breakers in the table then #4 aluminum would apply to both the 125 amp and 150 amp circuit breakers. Would this be correct?

 

[Dennis Alwon]

Look at the Table again. It states size not exceeding a size. If the overcurrent protective device is more than 100 amps and less than 200 amps then you use the 200 amp column. Thus #4 aluminum is needed

 

[jusme123]

...read the entire heading of the first column of that table, its states 'not exceeding'. As long as your breaker does not exceed the value listed in the first column, you are good to go if using that table, #4 is good

 

[deee]

Look at the Table again. It states size not exceeding a size. If the overcurrent protective device is more than 100 amps and less than 200 amps then you use the 200 amp column. Thus #4 aluminum is needed

I appreciate your response. Sometimes the wording throws me for a loop. I assumed that's what it meant but I wasn't sure. I shouldn't have dropped out of English 101 (LOL). Happy Thanksgiving.

 

[MasterTheNEC]

I appreciate your response. Sometimes the wording throws me for a loop. I assumed that's what it meant but I wasn't sure. I shouldn't have dropped out of English 101 (LOL). Happy Thanksgiving.

Might not help much....Sometimes the NEC and English 101 are at odds with each other.