nesparky,
Sorry that I wasn't clear in asking my question.
Article 430, specifically 430.6(A)(1) exception #3 clearly distinguishes between a '5hp motor' and an _appliance_ which contains a motor and has a '5hp' label on it.
This distinction carries through the sizing of conductors, selecting OCPD, sizing disconnect means, etc.
The question is: does this distinction also carry to plugs and receptacles? If I have an appliance with 15A 120V on the nameplate, can I put it on an L5-20 cord cap and receptacle, even if the appliance has a motor in it and a 6 hp label plastered to the outside?
My interpretation is that an appliance which draws 22A at 240V should be fine on a 30A receptacle. I fully agree that 7.5 hp 240V single phase general purpose _motor_ would require a much larger receptacle.
The reason that this distinction is important is that manufacturers seriously inflate the horsepower ratings of things like compressors. They don't lie, but they will plaster a '6 hp' rating on something if the power delivered at motor breakdown is 6 hp, even if the power delivered at normal full load is 2 hp. They want the high horsepower rating to make their machines seem more powerful.
Take a look at
http://www.sears.com/sr/javasr/prod...ES&bidsite=CRAFT&pid=00919541000 This is a '6 hp' compressor, but if you look at the detailed specifications, the compressor is rated at 15A on a 120V circuit. 15A times 120V is less than 2.5 hp even if we assume 100% efficiency and 100% power factor. If you calculate the mechanical output power from the SCFM rating, the mechanical power output is less than 0.5 hp. For application of article 430, you simply _cannot_ consider this a 6 hp motor. Dollars to donuts this compressor comes with a 5-15 or 5-20 plug.
-Jon
