OCP for fractional HP Motors

[GMAR519]

Am I looking at this correctly? With small fractional hp motors like 1/6 and 1/4 hp exhaust fan motors, that have internal thermal protection, the thermal protection would meet the 125% over current protection requirement and the supply breaker would be required to meet the 250% short circuit and ground fault protection requirement?

 

[augie47]

I think you will find 430.53 allows a branch circuit device to protect such motors without the 250% rule.

 

[GMAR519]

I think you will find 430.53 allows a branch circuit device to protect such motors without the 250% rule.

430-53 states that "...if all of the following conditions are met: (3) Individual overload protection conforms to 430.32" and 430.32 goes back to the 115/125% overload protection requirements.

 

[augie47]

430-53 states that "...if all of the following conditions are met: (3) Individual overload protection conforms to 430.32" and 430.32 goes back to the 115/125% overload protection requirements.

If they have thermal overloads as you noted in the OP, then they meet 430.32(A)(2) (assuming the mfg. sized them properly), so all you need to do is satisfy the GF/SC protection which takes you back to 430.53