You are watching: What size breaker to feed 125 amp sub panel
125 amp bus in a dashboard is pretty usual as the "low end" that is produced. If you desire to it is provided with just say a 60 amp feeder circuit, opportunities are you will certainly still only be able to find a panel with 100 or 125 amp bus. Nothing wrong with protecting it lower then it"s rating yet protecting 125 amp panel v 200 amp OCPD is a problem.
You have us presume the wire form for amperage of your 1/0; also assuming wire size for the calculate 75 amps. In short, calculated fill must it is in in accordance through the NEC. We aren’t assured below that the customer did together a thing. The said, check out NEC 310.15(B)(7). The has particular requirements, yet generally says in between 100-400A the feeder may be sized because that not much less than 83% that the company rating. If all is password compliant otherwise, sizing a 125A company feeder at 60% is not.
looking because that feed back, I at this time did an electrical inspection of increase grade 125 amp subpanel. In a 1br apartment. A 125 amp subpanel need a 1/0 feeder, the client is installation a undersized feeder come supply just the complete amp he will certainly be using, follow to his calculation he will be using about 75 amp only. Is installation allowed or go he has install the one 1/0 feeder indigenous the company to the subpanel come comply through the best 125 amp subpanel is rated for. Joe PMountain View
If the calculated fill is 75 amps using a 75 amp feeder is not undersized. The fact that the bus rating that the dashboard is 125 amps is irrelevant.
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