Thanks for the reply.
"Back-up fuses" are right from the IEC 947-2 that define their specs for MSP's (motor starter protectors.)
I guess the question should have been about the integration of IEC starters over NEMA and the affect it has on NEC.
The MSP's are rated to 100,000 amp short ckt breaking capacity under 6.3 FLA at 230 vac (the low end for ref.) If I wanted to use these beyond 6.3 amps I would need a back-up fuse based on their definition.
The trend currently (and will continue because of cost) is to use IEC versus the NEMA style. The MSP in conjunction with a contactor becomes an equivalent NEMA class starter.
Article 430-32 has the basic ol sizing guidelines for cd motors over 1 hp.
Interruptpting ratings; 110-9, 240-60, 240-83, and 240-86 are rather cryptic (lol, like most of the NEC sometimes.)
I just wanted some other viewpoints and opinions.
I do appreciate your post though.
Carl
