cord and plug connected equipment

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bryanbdp

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I know the code requires HP ratings for the plug and body used as a disconnect for a motor.
However, if you are connecting a machine, like a mill, that has a power switch built in, can you consider the built in switch as the disconnecting means, and just rate the plug and connector body for the load (non HP)? I see machines connected like this all the time, and it seems like none of the connector bodies are HP rated...
Thanks,
Bryan
 
bryanbdp said:
I know the code requires HP ratings for the plug and body used as a disconnect for a motor.
However, if you are connecting a machine, like a mill, that has a power switch built in, can you consider the built in switch as the disconnecting means, and just rate the plug and connector body for the load (non HP)? I see machines connected like this all the time, and it seems like none of the connector bodies are HP rated...
Thanks,
Bryan
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Just out of curiosity where does it say in the code that a connector used as a motor disconnect has to be horsepower rated? By implication you seem to be stating that if it is not used as a motor disconnect it would not have to be horsepower rated. I don't see how you can have a motor connected via such a connector without it being considered some kind of a disconnect.
 
petersonra said:
Just out of curiosity where does it say in the code that a connector used as a motor disconnect has to be horsepower rated? By implication you seem to be stating that if it is not used as a motor disconnect it would not have to be horsepower rated. I don't see how you can have a motor connected via such a connector without it being considered some kind of a disconnect.
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As I read 430.109(F), a HP rated cord & plug shall be permitted as the motor disconnecting means.
Where there is another means on disconnect, it might be arguable if the cord & plug would have to be HP rated.
 
After more research, i think the hp rating is required when the plug is the only visible/readily accessible means of disconnect. It sounds like the plug has to safely disconnect the motor under full locked rotor conditions. I think, if the equipment has a built in disconnecting means, that a plug and body rated at 125% of FLA would be ok. There don't seem to be any hp rated plug bodies, but i see them used all the time.
 
ALL
A similar discussion took place on this issue recently where the originator was directed to 400.10 Uses Permitted, for flexible cords.
Is the connection a motor or a piece of industrial equipment ?
 
Having read through the provisions of section 400.10 again, I think our installation would apply. The equipment is not fixed in place, and the nature of the shop is that equipment will be moved and replaced as needs change. The proper cable and ampacity must be followed, strain relief, and so on. Disconnecting a large motor under full locked rotor load would really be exciting, I think, thus the HP requirement when the plug/plug body are the only disconnect.
I have been unable to find twist lock plug bodies rated for any HP rating, the catalogs always note that the HP ratings only apply to the plugs and receptacles, not the plug bodies. Yet I see them used everywhere. I think the answer is in the specific use of the word "disconnect", not for convenience, not for lockout/tagout reasons, but to safely stop a motor under high load.
Other points of view?
 
I don't see how you can make a distinction between a disconnecting means that you only intend to be used under no load and one that can be used while loaded. The code just does not make that distinction anywhere that I can see. I agree it's a fairly common practice but I'm not convinced that just because it's common makes it code legal
 
Does make you wonder...
Does the NEC offer an illustrated guide or anything? Some of the IRC/IBC code books have a commentary you can purchase to make common concepts easier to apply.
 
bryanbdp said:
Does make you wonder...
Does the NEC offer an illustrated guide or anything? Some of the IRC/IBC code books have a commentary you can purchase to make common concepts easier to apply.
Click to expand...

There is a NEC Handbook with commentary and illustrations.

This for the 2017, but other years are available.

http://catalog.nfpa.org/NFPA-70-National-Electrical-Code-NEC-Handbook-2017-Edition-P16530.aspx

Note that not every code section is going to be expounded on and that any commentary is opinion and not code.
 
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