Motor KW Ratings

[YankeeShybull]

Forgive me if this has already been addressed, but I am new to the forum. With the NEC trying to push us in the metric units direction, why are motor KWs not listed in the FLC charts in the code. Mike's app also does not list them. I see more and more motors on a daily basis that only have KW listings.

 

[don_resqcapt19]

Based on Code Making Panel 11's response to my PI 3662 for the 2026 code that would permit the use of the nameplate current for motors that operate at voltages other than those shown in the motor current tables, you can't even use a motor marked only in kW in an NEC application.

The NEC contains the motor types and voltages approved for applications for the proper installation per this code. The addition of other motors cannot be accepted without further clarification on where they would be used and if they can be protected by the full range of motor controllers.

 

[YankeeShybull]

Again forgive me since I am new to this forum. The motors I am referring to are motors operating at standard voltages. but usually have been manufactured outside the US, and only have a KW rating, not HP. However all the tables in the NEC and Mikes App only reference HP. Many new motors from US companies have dual HP and KW ratings. Thus it would make sense to me to be able to reference FLC for KW only rated motors.

 

[infinity]

The motors I am referring to are motors operating at standard voltages. but usually have been manufactured outside the US, and only have a KW rating, not HP

Like Don stated they cannot be used in an NEC applicable application. This falls on the manufacturer who doesn't want to provide the nameplate information that would make the motor usable under the NEC.

 

[YankeeShybull]

Can you advise where in the NEC code it states that motors must have a HP rating and a KW only rated motor will not meet code?

 

[wwhitney]

Can you advise where in the NEC code it states that motors must have a HP rating and a KW only rated motor will not meet code?

430.7(A)(7).

However, the word "horsepower" there should be understood to mean "mechanical output power", and HP is just one unit for such an output power rating. kW is another reasonable unit. So if the motor is labeled with its mechanical output power in kW, I see no reason not to use the conversion of 1 KW = 1.341 mechanical HP to apply the NEC.

In other words, in the sentence "The motor horsepower is 1 horsepower," the two usages of the word horsepower have two different meanings. The first usage means "mechanical output power," while the second usage means "a unit equal to 745.7 joules/second."

Cheers, Wayne

 

[CoolWill]

Horsepower, inches, gallons. These things are part of why America is great. My truck gets 8000 furlongs per hogshead and that's the way I like it!

 

[YankeeShybull]

Thank you for your responses. I am still trying to understand how the code is pushing Degree C, Metric Conduit Sizes etc. but not moving to add KW rating for motors or mm2 for wire to tables that we have to reference frequently. I assume it all depends on who is on each code panel and their background, and not as a general movement for the entire code.

 

[jim dungar]

I am still trying to understand how the code is pushing Degree C, Metric Conduit Sizes etc. but not moving to add KW rating for motors or mm2 for wire to tables that we have to reference frequently.

NEC conversion to metric is not an organized effort. It moves in fits and starts. It has taken more than 40 years to get this far.

Wire sizes are a big deal in that it does not involve simply changing the unit of measure but the rather involves a physical size change and a resultant current carry capacity change.

 

[don_resqcapt19]

Thank you for your responses. I am still trying to understand how the code is pushing Degree C, Metric Conduit Sizes etc. but not moving to add KW rating for motors or mm2 for wire to tables that we have to reference frequently. I assume it all depends on who is on each code panel and their background, and not as a general movement for the entire code.

In general the members of the code making panels do not write code...they respond to public inputs asking for code changes.
The switch to include metric measurements a number of cycles ago was directed by the NFPA itself and not a result of public inputs. This was for marketing reasons with the NFPA wanting to sell more copies of the NEC outside of the US, there was no technical reason for the change.