69FIREBIRD
Member
Hi, I know this might be not quite the place to ask a question like this but I need to confirm how I should rate an isolator for machinery being shipped to the U.S. You guys in the U.S may be able to shed some light on this.
According to NFPA 79 5.3.3.1(6)(b) "where rated in horsepower the horsepower rating shall be at least equal to that which is defined by table 430.251(b) of NFPA 70 NEC for a locked rotor current equal to the largest sum resulting from the locked rotor currents of any combination of motors that can be started simultaneously and the full load current of the remaining motor and non motor loads that can be operated at that time."
So does that mean that my 40HP (45.5A @ 460V) motor (the only motor/load) according to table 430.251(B) having a locked rotor current of 290A @ 460V will require the main isolator to be rated at 290A @ 460V?
According to NFPA 79 5.3.3.1(6)(b) "where rated in horsepower the horsepower rating shall be at least equal to that which is defined by table 430.251(b) of NFPA 70 NEC for a locked rotor current equal to the largest sum resulting from the locked rotor currents of any combination of motors that can be started simultaneously and the full load current of the remaining motor and non motor loads that can be operated at that time."
So does that mean that my 40HP (45.5A @ 460V) motor (the only motor/load) according to table 430.251(B) having a locked rotor current of 290A @ 460V will require the main isolator to be rated at 290A @ 460V?