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Kevin, Licensed Electrical Contractor
Category: Electrical
Satisfied Customers: 3544
Experience:  30 years Licensed Electrical Contractor in Illinois, Adjunct College Electrical Instructor, Former Electrical Inspector, Diploma: Digital Electronics, FCC Technician License
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I have a situation where a 200A main breaker sub-panel is fed

Customer Question

I have a situation where a 200A main breaker sub-panel is fed from the main panel with a 200A breaker and 000 wire is this legel. The main panel breaker IT is set at 1500A and the sub-panel breaker IT is set at about 1200A
Submitted: 2 years ago.
Category: Electrical
Expert:  Kevin replied 2 years ago. name is ***** ***** I will be happy to assist you with your electrical question. My goal is to exceed your expectations on Just Answer!
1) A 200 amp feeder circuit requires a minimum of 2/0 Copper or 4/0 Aluminum. Keep in mind that this is the minimum conductor size per the National Electrical Code. A lengthy feeder circuit run will have a voltage drop and the conductors may need to be increased in size. NEC recommends that the voltage drop be at 3% or less.
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Customer: replied 2 years ago.
I need to know about the main panel breaker is it to small
Expert:  Kevin replied 2 years ago.
1) Sub-panel feeder breaker sizes are typically smaller than the main panel breaker size.
2) For example, a common home that has a 200 amp service will usually have a maximum of a 100 amp feeder breaker for a downstream sub-panel. This is a very common amperage ratio size from a main panel to a sub-panel.
3) If the main panel is 200 amp and installing another 200 amp feeder breaker for a downstream sub-panel, you basically have a "pass-thru" amperage and are allowing 100% of the 200 amp main to feed into the downstream sub-panel using a 200 amp double pole feeder breaker.
4) Sub-panels are sized according to the calculated connected loads.

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