IEC vs NEC and Allen Bradley Motor Protection Circuit Breakers

[jakeparsons03]

It seems like all Motor Protection Circuit Breakers have a fixed standard magnetic trip of 14x the rated current. From what I have gathered that is the IEC rating for instantaneous circuit breakers (I can't get my hands on a copy of the IEC). However the NEC here in north america has a maximum of 800% rating according to UL Table 31.1 and the NEC table 430.52(C)(1).

With how ubiquitous the Allen Bradley 140xx series is here in the US, there has to be something I am missing on the legality to use these. The only way I could see them being used is on Design B premium efficiency motors according to 430.52(C)(3)(b)(2)(b), where the max is 1700%. What am I missing here?

 

[jakeparsons03]

I figured it out. I kept looking at the 140MT series which has a 14xIe. The 140M series has a 13xIe which is compliant with 430.52(C)(3)(b)(2)(a) and (b).

 

[david luchini]

I figured it out. I kept looking at the 140MT series which has a 14xIe. The 140M series has a 13xIe which is compliant with 430.52(C)(3)(b)(2)(a) and (b).

The 140M series is discontinued...140MT is the recommended replacement.

 

[jakeparsons03]

The 140MT doesn't show as being certified by the NEC, which makes sense as its trip current is too high. It shows as being UL Listed for complying with code in America is that enough? I have read UL508 and it looks to follow the NEC, however I have a 2001 edition. It could be different in more recent revisions.

 

[petersonra]

Hint - Look in the code for type E and F combination motor controllers instead of circuit breakers.