Overload relay trip class


Thread Starter

TM Guy

I have several motors that are driving air fans. The HP rating are from 1.5HP to 30HP. Can someone help me on the overload trip class selection for the overload relays? Or tell me where I can find information on this subject? Thanks.

Bouchard, James \[CPCCA\]

Overload classes are covered in NEMA ICS 2-222 and indicates how fast the overload will trip. A Class 10 will trip in 10 seconds at 600% of its rating. Class 20 is 20 seconds and class 30 is 30 seconds. General use is class 20.

You can also find this in the industrial controls catalog of many starter suppliers (I took it from Allen Bradley).

James Bouchard