I am looking at a design that incoporates a 1200Amp (42kAIC) Maintenance Bypass Cabinet which is fed from utility. The customer wants a 50Amp breaker placed in the MBP to feed a xfrmr for a 120/208 general purpose panel. The MBP is fed directly from a 2500amp panelboard (100kAIC). My concern with this approach is should there be a fault, would the 1200amp MBP breaker be likely to fail? My thinking is to place the 50Amp breaker in the 2500amp panelboard and feed the xfrmr that way, as the kAIC is much higher in the 2500A panelboard, and should there be a fault, they are less likely to drop their main breaker and drop the MBP feed altogether. Any thoughts would be greatly appreciated.
Overcurrent Fault Sensing
- Thread starter JHelms
- Start date
- Status
ron
Senior Member
- Location
- New York, 40.7514,-73.9925
What is the calculated fault current at the MBP Cabinet and 2500A Pnl?
kingpb
Senior Member
- Location
- SE USA as far as you can go
- Occupation
- Engineer, Registered
If it's 480V (not mentioned), at 2500A to get to 100KAIC you'd need a 2000kVA transformer with a 2.5% impedance.
An unlikely (not impossible) scenario.
Need a lot more info.
An unlikely (not impossible) scenario.
Need a lot more info.
- Location
- Lockport, IL
- Occupation
- Retired Electrical Engineer
I don't understand the setup. You speak of a cabinet, then you speak of a MBP, and you speak of a panelboard. You speak of 42KAIC ratings and 100KAIC ratings. What is connected to what? What are you trying to connect to what? A sketch would be invaluable. 
- Status