During a recent audit we found two pieces of equipment fed of the same 600V 40A bus plug. One of the machines has a 50A main breaker and the second has a 30A breaker. Each piece of equipment has an FLA of 13.2A, for a total max load of 16.4A. My concern is that I was always taught that your bus plug and fuse has to be rated to the equipments main protective device and not the load. I have a copy of the 2005 NEC but can't find where it defines the correct article to address the proper feed method. I'm thinking the correct solution is to change the main breaker of each piece of equipment to a 20A main.
Correct Bus Feed Fusing and Branching
- Thread starter fmatthew
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If these are motor loads then the branch OCPD is allowed to be larger to allow the motor to start without tripping the breaker. This is still a safe system because the motor has
overload protection, the breaker is for short circuit and ground fault protection.
overload protection, the breaker is for short circuit and ground fault protection.
If each of the machines has a "main breaker", i would think that would be the protection for the machine. The buss plug would protect the feeder to those machines and would be sized accordingly (240.4, 430, etc.)
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