Portable 240v compressor plug

[zr52002]

I just bought this portable air compressor. It's 240v, the write-up on Zoro/Grainger calls it 3.0 HP, the label on the compressor calls it 3.5 HP, and the motor nameplate says 3.7 HP and 17.2 FLA. There's basically no manual provided with this thing at all.

It's got a really stiff 14 gauge cord with a 6-20p on it. Which ... 6-20p is only rated to 2 HP motors. But I guess that's NEC compliant ok because it comes that way from the factory?

Both locations I intend to use it at have L6-30r receptacles, and I'd like to convert the compressor to that. And swap the cord for 12 gauge SOOW or SJOOW. The L6-30 is also only rated to 2HP, but is that ok in this case since it came from the factory with a plug with the same rating?

It sure seems like I'm improving safety by going to a bigger cord and a locking plug, but maybe there's something I'm missing here. Replacing the receptacle isn't really an option because I use it with other tools at times and need the 30a plug for that, and I'd rather not run another circuit either.

 

[American Locomotive]

It will be fine. A lot of the "portable" 2-3HP class 240v compressors come with 6-20P plugs.

 

[nadogail]

IMHO, an over rated plug on your compressor will not hurt anything.

The maximum current draw is controlled by the motor.

Changing the gage of the supply cable wire should not make any significant difference either.

I am not an expert; I just have enough knowledge to be dangerous.

 

[cannuck]

You should be able to run 5 HP @ 230V through a 30A twist-lock....BUT: Did I read 14ga conductor!!!???? No way 20 Amps will go down 14ga or 12ga wiring. I would expect 9 ga for single conductor and 8 ga for multi-conductor cable. Keep in mind, I am the mechanical guy in an electric bunch, but some of their stuff kind of rubs off on me.

 

[Norcal]

You should be able to run 5 HP @ 230V through a 30A twist-lock....BUT: Did I read 14ga conductor!!!???? No way 20 Amps will go down 14ga or 12ga wiring. I would expect 9 ga for single conductor and 8 ga for multi-conductor cable. Keep in mind, I am the mechanical guy in an electric bunch, but some of their stuff kind of rubs off on me.

Not under the NEC.

 

[cannuck]

Not under the NEC.

I assume because starting loads exceed 30A? What does NEC say about??

 

[nadogail]

If the manufacture supplied power cable is 14 gauge, it should be enough to run the equipment.

 

[cannuck]

If the manufacture supplied power cable is 14 gauge, it should be enough to run the equipment.

If the NEC won't allow 5 HP on 30A cord how could you run 3HP on 20A???? Found a table for SOW, SOOW, SJOW, etc. and 14 ga. should be good for 18A @ 230V single phase. Seems a bit light draw for 3 HP, never mind 3.5 or 3.7 and the 17.5A it claims to draw. Wonder if the same people write the data plate that make "5HP" shop vacs that run on 120V 15A breakers?

 

[nadogail]

If the NEC won't allow 5 HP on 30A cord how could you run 3HP on 20A???? Found a table for SOW, SOOW, SJOW, etc. and 14 ga. should be good for 18A @ 230V single phase. Seems a bit light draw for 3 HP, never mind 3.5 or 3.7 and the 17.5A it claims to draw. Wonder if the same people write the data plate that make "5HP" shop vacs that run on 120V 15A breakers?

Probably So.

 

[Zeke]

Change the voltage to 120v and the wire size increases. I get old light fixtures from Europe that ran on one leg of 230v and use 20 ga wire.

 

[zr52002]

IMHO, an over rated plug on your compressor will not hurt anything.

It's more plug than the compressor came with from the factory, both plugs are only rated to 2HP motors so technically under-rated in that regard.

Since I'm upgrading to both a higher-rated plug and a heavier gauge wire, I'm not too worried about it.

 

[mike93lx]

Change the voltage to 120v and the wire size increases. I get old light fixtures from Europe that ran on one leg of 230v and use 20 ga wire.

Europe doesn't use split phase 230v, AFAIK. They are 230v hot to neutral

 

[Zeke]

^^^That's what I meant but said it wrong. By "one leg" I meant the hot.

Single phase or 3 phase people understand. Split phase was something that I didn't hear many years ago when describing American vs. Euro electrical systems. But yes, they have single phase 230v for residential but they do have secondaries as many appliances run on 400v.

 

[beemerphile]

I assume because starting loads exceed 30A? What does NEC say about??

No, it has to do with the cord being the disconnecting means for the circuit. It is no problem if the motor is OFF when you yank the plug, but if it is running and you were to use the cord as the disconnecting means, then a motor acts differently than a resistive load when the electrical contacts separate. That is why larger cord connected motors require a disconnect that is mechanically interlocked so that the cord cannot be removed unless the circuit is deenergized.

EDITED TO ADD: Look at NEC 430.109 (F) for guidance on cord and plug connected motors. The HP rating is required if the cord and plug are the disconnecting means. If there is another principle disconnecting means, then you can go by current ratings for the assembly. You'd want to make sure that the disconnect is local and obvious. The interlocking of the disconnect with the cord removal insures compliance and would limit the possibility of injury if someone tried to remove the cord from a malfunctioning motor which could be drawing locked rotor amps.

 

[Norcal]

^^^That's what I meant but said it wrong. By "one leg" I meant the hot.

Single phase or 3 phase people understand. Split phase was something that I didn't hear many years ago when describing American vs. Euro electrical systems. But yes, they have single phase 230v for residential but they do have secondaries as many appliances run on 400v.

The normal voltages are 400Y/230V, some dwellings are only supplied with 230V which is line to neutral, in Germany they get 400/230V & electric ranges are 400V 3Ø.