When supplied from a 120/208-volt, 3Ø, 4-wire panelboard, the maximum size ITCB for the motor branch circuit is what?

The maximum size instantaneous trip circuit breaker (ITCB) for a motor branch circuit fed from a 120/208-volt, 3-phase, 4-wire panelboard is determined based on the National Electrical Code (NEC) guidelines. In general, the ITCB size must be rated according to the branch circuit conductors and the applicable motor loads that will be served.

When selecting the appropriate breaker for a motor branch circuit, we consider the full-load amperage (FLA) of the motor and verify compliance with the NEC, particularly the sections that deal with the overload protection of motors. For a typical three-phase motor circuit, the breaker can be sized to handle the starting currents that exceed the full load current, but must also ensure adequate protection.

In this context, the maximum size ITCB for a motor branch circuit often aligns with safety and allows for specific loads, ensuring that it can handle the currents without nuisance tripping while still providing adequate protection for the wiring and equipment.

Thus, if the maximum size ITCB given is 70 amps, it provides the necessary protection and is compliant with the codes for typical applications fed from a 120/208V source, especially when operating certain motor sizes that demand a higher current allowance during start