ezdrocks
Member
- Location
- Houston, Texas, USA
- Occupation
- I&E Designer, Industrial Electrical and Instrumentation design (NOT an engineer but close)
All,
I am an I&E designer for an engineering company. For a current design, I'm pulling a main, 12,470V feeder from a PSE (Dead front pad mounted switch gear) located beneath a power pole, above ground in cable tray (tray will have a cover to protect conductors) to a new MCC Building. The main feeders will hit a HVL-CB breaker, before then going out to the 2,000kVA transformer. I am having an argument with our EE about the size of the cable to pull. For note, the distance of the pull is less than 500'. From what I gather in the NEC, from table 310.60(C)(67), using 3-1/C #2 cables (plus a ground) is fine (I could actually use #4). However, our engineer is quoting table 240.92(B) and using that calculation to say we need to pull 3-2/C #3/0 cables (with ground) due to short circuit protection.
I argued that 240.92(B) references back to 240.21 (B)(2), (B)(3), and (B)(4), but our installation does not fall under those references, therefore, we don't have to size the cable based on short circuit.
Can someone explain who's right in this scenario.
For reference, I have been doing this 12 years, and although I am not an Electrical Engineer, I have a lot of experience working with a different engineer with over 30 years experience. The engineer at my new work comes from a background of city planning engineering and is not used to the way things are done in an industrial setting.
I am an I&E designer for an engineering company. For a current design, I'm pulling a main, 12,470V feeder from a PSE (Dead front pad mounted switch gear) located beneath a power pole, above ground in cable tray (tray will have a cover to protect conductors) to a new MCC Building. The main feeders will hit a HVL-CB breaker, before then going out to the 2,000kVA transformer. I am having an argument with our EE about the size of the cable to pull. For note, the distance of the pull is less than 500'. From what I gather in the NEC, from table 310.60(C)(67), using 3-1/C #2 cables (plus a ground) is fine (I could actually use #4). However, our engineer is quoting table 240.92(B) and using that calculation to say we need to pull 3-2/C #3/0 cables (with ground) due to short circuit protection.
I argued that 240.92(B) references back to 240.21 (B)(2), (B)(3), and (B)(4), but our installation does not fall under those references, therefore, we don't have to size the cable based on short circuit.
Can someone explain who's right in this scenario.
For reference, I have been doing this 12 years, and although I am not an Electrical Engineer, I have a lot of experience working with a different engineer with over 30 years experience. The engineer at my new work comes from a background of city planning engineering and is not used to the way things are done in an industrial setting.