Motor Rated in KW

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nhee2

Senior Member
Location
NH
A vendor has initially proposed supplying pumps with a rating in KW. (50KW). In some initial correspondence he has been unable to confirm what is the HP rating of the proposed motor. Although we can easily convert KW to HP, it appears that 430 does not explicitly address sizing of conductors/OL/OCPD for KW rated motors. Would the correct application be to convert 50KW to HP (37.5) and then use the next size up (40 HP) in table 430.250? 430.6.(A)(1) allows you to apply the tables using nameplate amps if not marked in HP. I just haven't had to do that before.

Assuming the pump assembly includes applicable listings/labeling etc.
 

Besoeker

Senior Member
Location
UK
A vendor has initially proposed supplying pumps with a rating in KW. (50KW). In some initial correspondence he has been unable to confirm what is the HP rating of the proposed motor. Although we can easily convert KW to HP, it appears that 430 does not explicitly address sizing of conductors/OL/OCPD for KW rated motors. Would the correct application be to convert 50KW to HP (37.5) and then use the next size up (40 HP) in table 430.250? 430.6.(A)(1) allows you to apply the tables using nameplate amps if not marked in HP. I just haven't had to do that before.

Assuming the pump assembly includes applicable listings/labeling etc.
50kW is 67 HP.
I think you applied the conversion factor the wrong way round.
 

Besoeker

Senior Member
Location
UK
Yes, I screwed that up. 67 HP would be equivalent.
No problem. As I've posted here before, my late great friend Tommy was fond of saying, the man who never made a mistake never made anything.

A little aside.
He was a great character and quite an influence on my professional life. He worked for me for a good many years as a contracts manager. Attention to detail was second to none. He had previously worked for Rolls Royce aero division. Mistakes on that were not an option.

He also happened to be a close neighbour and so were personal friends as well as colleagues. And my kids loved him.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
many european motors also have HP ratings.

sometimes the nameplate reflects this and sometimes not.

I have seen motors where there is a sticker put over the original nameplate showing what its US rating is.

I have also heard that if you ask, sometimes they will send you a replacement NP that is US rated.
 

iwire

Moderator
Staff member
Location
Massachusetts
Does the NEC apply to manufacturers?
If not, won't US motor manufacturers still rate their products in HP?

The problem is the NEC requirements for installers and designers to wire motors are based on HP not KW. It seems the NEC should have provisions for KW rated motors. :)
 
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