my comuster want have the semi-stationary air commpressor to be hook up with the repectale and plug in.
I did look at it and it is 7.5 hp single phase @ 240 volts 22.4 amps running amps current.
this part i am kinda relecut to do this, because i did look up the Pass and Seymour catalog book and have footnote for hp rating for 6-30R and the 6-30P they are restricted to 2 hp only and i will like your options here.
myself i rather hardwired without the plug/repectiale attachments on it. for safety reason due the current drawage and can overheat the plug at that rating.
please let me know what you think ??
merci , marc
Pas de problme,il marche n'est-ce pas?"(No problem, it works doesn't it?)
Hey Bob, I'm just wondering? Do the US receptacles of these type, have an Inter-locking mechanism in them? As in, so that you can't attach or remove the plug, unless the supply is turned off?. These sorts of connectors are expensive anywhere, I think, I was recently quoted NZ$350 for a set like this, the guy I was doing the job for nearly died!.
Re: Air Commpressor repecticale#36866 04/17/0406:13 PM04/17/0406:13 PM
I was just reading a question on cord and plug connected air compressors at 'doityourself.com', when I remembered this thread. So I went and did some code re-reading and some calculating.
1) Air compressors, like vacuum cleaners and stereo amplifiers, often have their ratings 'pumped up' by the marketing department. I've seen '5.0 Hp' vacuum cleaners with 5-15 cord caps on their power cords.
2) 22.4A * 240V = 7.2 Hp if you presume 100% power factor and 100% efficiency, neither of which is true. Therefore this air compressor is _not_ a 7.5 Hp machine.
3) Take a look at 430.6(A)(1) exception #3: "For a listed motor-operated appliance that is marked with both motor horsepower and full-load current, the motor full-load current marked on the name-plate of the appliance shall be used instead of the horsepower rating on the appliance nameplate to determine the ampacity or rating of the disconnecting means, the branch-circuit conductors, the controller, the branch-circuit short circuit and ground-fault protection, and any separate overload protection."
I presume that the difference is that a listed appliance has a much better defined mechanical load placed on the motor, so the listing agency can limit the startup overload and less strain is expected on the supply components.
If this compressor were sold as an integral unit with the motor built in, and the name-plate current is 22.4A, then I would think it would be just fine on a 6-30 or L6-30 receptacle.
Could someone else confirm this interpretation?
Re: Air Commpressor repecticale#36868 04/25/0408:53 PM04/25/0408:53 PM
Winnie i believe you missed part of marc's first post quote this part i am kinda relecut to do this, because i did look up the Pass and Seymour catalog book and have footnote for hp rating for 6-30R and the 6-30P they are restricted to 2 hp only and i will like your options here.
Un quote Many receptacles have a HP limit in the manufacturers instructions. You could still cord and plug connect the compressor but the cost will be high. The only real reason to do that is if the customer will be moving the compressor from place to place. Not in the case described.
Re: Air Commpressor repecticale#36869 04/25/0410:05 PM04/25/0410:05 PM
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.
Re: Air Commpressor repecticale#36870 04/26/0403:01 AM04/26/0403:01 AM
You would have to be very careful playing that game. If the compressor came from Big Orange or the like, the rating is inflated to just under the point where it could be called fraud. I have a vintage Binks compressor with a compressor duty 7.5 HP motor. It draws a little better than 30 amps running. There is a lot of difference between homeowner and commercial duty. This has been interesting for me because I run mine on a 6-50 outlet and never gave the HP rating thing a thought. I've never considered it as a disconnecting means. That's what the mag starter and breakers are for. I don't think I'll change mine but I probably would not install a similar setup for a customer now.