Motor Overloads question. NEC 430.32

[kc_hubbs]

I was recently talking to someone about this part of the code, and we have a disagreement over how to interpret the code.

When sizing the overloads, the code states that a motor with a service factor of 1.15 or more can use 125%/140%. It also states that a motor with a temperature rise of 40 degrees Celsius or less can use the 125%/140%.

I read the code as saying that motor only needs to me meet one of those requirements, not both, to be able to use the 125%/140% rating. The other electrician tells me the motor does have to meet both.

Can anyone shed some light please ?

 

[charlie b]

I agree with you. The word "and" does not appear in either section. It says that a motor with XXX can use this value, and then it says that a motor with YYY can use this value. Those are separate statements, and are not related to one another.

Welcome to the forum.

 

[kc_hubbs]

Thank you for your reply.

I had the exact same thoughts as you. Their comeback was that the code doesn't use the word "or" either in the statements.

Thanks again for your reply.

 

[kwired]

I am seeing a possible mix up and combining of sections that are separate requirements for separate applications.

430.32 has different subsections for different applications.

A is for motors over 1 HP 125% applies most of the time for separate overload, 140 to 170% can apply to an integral thermal overload

B is for one horsepower or less - automatically started, also has different requirements for different conditions.

C allows you to increase A 1 or B 1 if they don't allow the motor to start (might be where you got the 125/140 from in OP?)

D is for one horsepower or less non automatically started

 

[kc_hubbs]

Sorry for the delay in replying to this.

I was looking at section A and section C since all motors i deal with are over 1HP. The code is a little unclear on when I can use the 115% vs the 125%(or the 130% vs 140% from section 3). Does the motor have to have a service factor of 1.15 or higher AND have a temperature rise of 40 degrees Celsius of less, or does it only have to meet one of those qualifications ?

 

[jumper]

Sorry for the delay in replying to this.

I was looking at section A and section C since all motors i deal with are over 1HP. The code is a little unclear on when I can use the 115% vs the 125%(or the 130% vs 140% from section 3). Does the motor have to have a service factor of 1.15 or higher AND have a temperature rise of 40 degrees Celsius of less, or does it only have to meet one of those qualifications ?

You only have to meet one or the other, not both.

 

[kwired]

Sorry for the delay in replying to this.

I was looking at section A and section C since all motors i deal with are over 1HP. The code is a little unclear on when I can use the 115% vs the 125%(or the 130% vs 140% from section 3). Does the motor have to have a service factor of 1.15 or higher AND have a temperature rise of 40 degrees Celsius of less, or does it only have to meet one of those qualifications ?

I'm confused on what section 3 you are addressing - if you meant section C your question makes sense and the answer is either condition is allowable.

Note the confusing part of applying this is that most your overload tables or the dials on adjustable oveloads already account for 125%. You just set them for motor FLA and 125% is already built into the setting/selection.

If A doesn't allow motor to start you can't just multiply motor nameplate by 1.4 and set an adjustable dial to the result - the actual current setting will be 25% higher.

Also see informational note - class 10 overload will trip in less time then class 20, this often comes into play for loads that take time to accelerate.