spiritblood
New member
- Location
- Houston,TX
Hello everyone, this is my first post on Mike Holt's Forum. I appreciate all the helps!
My question is which of the following articles we should use when size the MCC Main circuit breaker under 800Vac:
1. 430.62 + 430.94, 430.62 is defined for Motor Feeder Short-circuit and Ground-fault protection, its exception no.2 states Where the feeder overcurrent protective device also provides overcurrent protection for a Motor Control Center, the provisions of 430.94 shall apply; and 430.94 basically tells us that the Amp rating for OCPD shall not exceed the rating of the common power bus. So my understanding is the feeder protection shall be sized NO GREATER than the Largest rating of branch circuit short-circuit and ground-fault protective device + FLA of other motors, but the sum needs to be less than the common bus. The 430.62 did not mention any loads other than motors. 430.94 basically directs us to 240.4
2. 215.3 defines Feeder Overcurrent Protection. It covers a broader range than 430.92+430.94 in my opinion, as this article applies to all feeder protection rather than only the Motor related feeder protection. 215.3 uses the concept of "continuous" or "non-continuous" to define how a feeder protection needs to be sized, which is NO LESS than 125% of continuous load + 100% of non-continuous load.
The option 1 has a concept of NO GREATER THAN, whereas the option 2 has a concept of NO LESS THAN. Should we apply both codes when size the MCC Main breaker, or use only one of them? In either case, I know 240.4 has to be followed, the MCC main breaker has to be no greater than the common bus, but I want to be able to size the main breaker as close as possible without nuisance trip. Thanks a lot for your time, any help is greatly appreciate it!
Hello everyone, this is my first post on Mike Holt's Forum. I appreciate all the helps!
My question is which of the following articles we should use when size the MCC Main circuit breaker under 800Vac:
1. 430.62 + 430.94, 430.62 is defined for Motor Feeder Short-circuit and Ground-fault protection, its exception no.2 states Where the feeder overcurrent protective device also provides overcurrent protection for a Motor Control Center, the provisions of 430.94 shall apply; and 430.94 basically tells us that the Amp rating for OCPD shall not exceed the rating of the common power bus. So my understanding is the feeder protection shall be sized NO GREATER than the Largest rating of branch circuit short-circuit and ground-fault protective device + FLA of other motors, but the sum needs to be less than the common bus. The 430.62 did not mention any loads other than motors. 430.94 basically directs us to 240.4
2. 215.3 defines Feeder Overcurrent Protection. It covers a broader range than 430.92+430.94 in my opinion, as this article applies to all feeder protection rather than only the Motor related feeder protection. 215.3 uses the concept of "continuous" or "non-continuous" to define how a feeder protection needs to be sized, which is NO LESS than 125% of continuous load + 100% of non-continuous load.
The option 1 has a concept of NO GREATER THAN, whereas the option 2 has a concept of NO LESS THAN. Should we apply both codes when size the MCC Main breaker, or use only one of them? In either case, I know 240.4 has to be followed, the MCC main breaker has to be no greater than the common bus, but I want to be able to size the main breaker as close as possible without nuisance trip. Thanks a lot for your time, any help is greatly appreciate it!
My question is which of the following articles we should use when size the MCC Main circuit breaker under 800Vac:
1. 430.62 + 430.94, 430.62 is defined for Motor Feeder Short-circuit and Ground-fault protection, its exception no.2 states Where the feeder overcurrent protective device also provides overcurrent protection for a Motor Control Center, the provisions of 430.94 shall apply; and 430.94 basically tells us that the Amp rating for OCPD shall not exceed the rating of the common power bus. So my understanding is the feeder protection shall be sized NO GREATER than the Largest rating of branch circuit short-circuit and ground-fault protective device + FLA of other motors, but the sum needs to be less than the common bus. The 430.62 did not mention any loads other than motors. 430.94 basically directs us to 240.4
2. 215.3 defines Feeder Overcurrent Protection. It covers a broader range than 430.92+430.94 in my opinion, as this article applies to all feeder protection rather than only the Motor related feeder protection. 215.3 uses the concept of "continuous" or "non-continuous" to define how a feeder protection needs to be sized, which is NO LESS than 125% of continuous load + 100% of non-continuous load.
The option 1 has a concept of NO GREATER THAN, whereas the option 2 has a concept of NO LESS THAN. Should we apply both codes when size the MCC Main breaker, or use only one of them? In either case, I know 240.4 has to be followed, the MCC main breaker has to be no greater than the common bus, but I want to be able to size the main breaker as close as possible without nuisance trip. Thanks a lot for your time, any help is greatly appreciate it!
Hello everyone, this is my first post on Mike Holt's Forum. I appreciate all the helps!
My question is which of the following articles we should use when size the MCC Main circuit breaker under 800Vac:
1. 430.62 + 430.94, 430.62 is defined for Motor Feeder Short-circuit and Ground-fault protection, its exception no.2 states Where the feeder overcurrent protective device also provides overcurrent protection for a Motor Control Center, the provisions of 430.94 shall apply; and 430.94 basically tells us that the Amp rating for OCPD shall not exceed the rating of the common power bus. So my understanding is the feeder protection shall be sized NO GREATER than the Largest rating of branch circuit short-circuit and ground-fault protective device + FLA of other motors, but the sum needs to be less than the common bus. The 430.62 did not mention any loads other than motors. 430.94 basically directs us to 240.4
2. 215.3 defines Feeder Overcurrent Protection. It covers a broader range than 430.92+430.94 in my opinion, as this article applies to all feeder protection rather than only the Motor related feeder protection. 215.3 uses the concept of "continuous" or "non-continuous" to define how a feeder protection needs to be sized, which is NO LESS than 125% of continuous load + 100% of non-continuous load.
The option 1 has a concept of NO GREATER THAN, whereas the option 2 has a concept of NO LESS THAN. Should we apply both codes when size the MCC Main breaker, or use only one of them? In either case, I know 240.4 has to be followed, the MCC main breaker has to be no greater than the common bus, but I want to be able to size the main breaker as close as possible without nuisance trip. Thanks a lot for your time, any help is greatly appreciate it!