Nameplate Ratings

[Charlie S.]

So I have a question about a disagreement that we have within our company. It is in regards to nameplate ratings on machines such as plastic injection machines or pump skids. In any case, the machine is made up of multiple motors and other equipment that has been engineered, assembled and delivered to a job site and needs nothing more than a feeder brought in to the main electrical cabinet to power up the machine. Let's say the nameplate specs out 496 FLA. Now this is a machine that will operate longer than 3 hours. Is it necessary to calculate 125% of nameplate due to the fact that this is considered a continuous load? Or, have the proper calculations already been figured into the nameplate rating and run wires and fuses rated at 500 amps and call it a day? I've called this company and they said it is figured as necessary and a co-worker called and got a different tech that said add the 125%. What has been your experiences as electricians and engineers on this equipment that comes fully built with nameplate ratings? Any feedback is appreciated...especially feedback with authoritative evidence.

 

[Hv&Lv]

430.32 says 125% of nameplate rating, so that’s what I use.

haven’t done one in about 4 years though...

 

[Charlie S.]

430.32 says 125% of nameplate rating, so that’s what I use.

I agree with 125% of nameplate for one motor. However, where more than 1 motor is present the code states that we are supposed to take 125% of the largest motor plus the sum of the FLC's of the remaining motors (430.24). So in my situation, it would seem that taking 125% of the nameplate would be taking every motor on the machine (plus everything that is not motor load) at 125%. To me this would be overkill and unnecessary. Can you think of any other code reference that would suggest 125% of a machine made up of multiple components? Thanks for your thoughts and interaction!

 

[texie]

See 430.7(D)(1). The data plate on the machine should have minimum circuit ampacity and Maximum OCPD listed on the label. In many cases with industrial machinery such as you describe the minimum circuit ampacity could be less than the sum of all loads because of load diversity in the way the machine operates. This is one reason the NEC wants the manufacturer to calculate the minimum circuit ampacity.

 

[Charlie S.]

See 430.7(D)(1). The data plate on the machine should have minimum circuit ampacity and Maximum OCPD listed on the label. In many cases with industrial machinery such as you describe the minimum circuit ampacity could be less than the sum of all loads because of load diversity in the way the machine operates. This is one reason the NEC wants the manufacturer to calculate the minimum circuit ampacity.

I agree with this 100%. If the manufacturer would always list OCPD that would make life a lot easier. I often run into issues like you see on this nameplate. If you do the math on the Rate Power -vs- FLC it would appear as though engineering was calculated higher than 125%. So my opinion is to take something like this and protect it at 500 amps and be done. However, "my opinion" does not always equal acceptable code. I do think this is the closest code reference that deals with my situation though. Thanks for feedback!

 

[texie]

I agree with this 100%. If the manufacturer would always list OCPD that would make life a lot easier. I often run into issues like you see on this nameplate. If you do the math on the Rate Power -vs- FLC it would appear as though engineering was calculated higher than 125%. So my opinion is to take something like this and protect it at 500 amps and be done. However, "my opinion" does not always equal acceptable code. I do think this is the closest code reference that deals with my situation though. Thanks for feedback!

Maybe you should inquire as to why the machine labeling does not comply with the NEC. Are these machines listed by an NRTL? Often industrial machinery is offered with or without listing. In some jurisdictions listings are required while some "look the other way" at industrial installations.
I would suspect that in your case you may have over-sized conductors which is wasteful but also has some down sides such as increasing available fault current at the terminals of the machine.

 

[Another C10]

My take on this for what its worth .. FLA, Full Load Amps or Full Locked Amps is it .. That reading I'm pretty darn sure was the calculation measured under a FLA condition, ya might still want to add the 125% merely for the in rush draw characteristics, although pretty sure that's for the first 30 seconds or so. I'm not a motor expert although I was taught FLA is pretty much the max. just my 2 cents ..

 

[infinity]

By definition in Article 100 a continuous load has to be running at it's maximum for at least 3 continuous hours. If any part of the process allows for a single compnent to run at less than it's maximum ampacity even for one second it would not fit the definition of a continuous load.