Current Rating of cord/plug connected machine on branch circuit

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Marlow

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I hope I chose the correct sub-forum for this question.


A hobby woodworker has a number of woodworking machines in his garage. He had a 240 volt 20 amp 3 wire circuit installed in the garage with 4 outlets. This woodworker buys a piece of equipment that is provided by the manufacturer without a cord and plug set. This item is rated at 21 amps. He attaches a length of SJOOW 12/3 cord and a 20 amp plug to the machine and uses the machine on the aforementioned circuit without incident.


Question: are there any rules being broken here, and if so, what are they. Is there an NEC rule at play here, or is there some other regulation (e.g., UL) that is being violated?
 
Marlow said:
This woodworker buys a piece of equipment that is provided by the manufacturer without a cord and plug set.
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My first thought is does the manufacturer of these machines permit cord and plug connections or must it be hardwired?
 
Marlow said:
Question: are there any rules being broken here, and if so, what are they. Is there an NEC rule at play here, or is there some other regulation (e.g., UL) that is being violated?
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The machine probably never reaches full-load current. If it ain't broke . . .
 
I would think the breaker would trip before anything could get hot enough to cause damage. But I also agree, it won't ever reach 21A.
 
Let me give you a little background. Much like this forum, there are a number of forums I participate in that focus on woodworking. Quite often, questions come up regarding electrical issues such as this. I am only vaguely familiar with the NEC, but my very basic understanding is that the electrical code pertains to the electrical infrastructure in (in this case) a dwelling. It focuses on everything upstream of the receptacle to the power company service drop. I was under the impression that it did not, for example, apply to the ampacity of power cord connected to a device or the plug connected to this power cord. I am guessing that this is governed more by UL standards? However, I am wondering if, assuming that the mfg allows this device to be connected via cord and plug, with the understanding that this equipment is not permanently installed, does any NEC rule have jurisdiction over the use of a device on a circuit such as this where the current rating of the device exceeds the rating of the circuit you are connecting to? In this particular case, I have measured the current draw under partial load conditions and it runs around 10 amps, so no problem there. But I am more interested in the "by the book" rules governing this sort of situation.
 
If the mfg instructions say to add a cord, they certainly would have to give you the minimum size for it. If they say to hardwire it, then you would go by the NEC rules for circuit sizing and OCPD.

So to the OP, without seeing the mfg instructions, I can only say there is a violation of not providing correct OCPD and conductors for the required load. Especially if there is a nameplate with the current rating on it. I'm guessing that's where the 21A came from.
 
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