I had planned on putting a compressor just outside of my garage, underneath some stairs, and plumbing it inside. I put a 30 amp 220v plug there just for this purpose. But now the wife is having no part of that, since she claims the "outside" (i.e. yard) is hers and the inside (garage) is mine and she doesn't think the compressor goes with her landscape plan. I can put it under the stairs if I build an enclosure for it, but I am leaning towards just putting it inside, as I have room for it. What I'm probably going to purchase is something along the lines of a220/230v 2-stage IR 5hp with a 60 or 80 gal tank. Rather than running a new electrical line inside the garage, I am wanting to simply use the 50 amp welder outlet that I also had installed during construction. Question: if the compressor calls for a 30 amp service, is there any problem with just changing the plug/wire on the compressor and leaving the outlet and breaker at 50 amps. The romex wire is properly sized for 50 amps. If the compressor comes with a separate starter, would the starter have the overload/breaker built into it? Or do I need to change the outlet and breaker? I'd prefer not to, so I can use the same plug for both the compressor and welder.
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Compressor Wiring
- Thread starter tampascl
- Start date
Charles (in GA)
Well-known member
You want to put a plug on the compressor cord, much like the welder has? This is akin to plugging a lamp in a receptacle, then later unplugging it and plugging in the vacuum cleaner. I don't think the code limits or restricts you in this since it is not a dedicated circuit. I may be wrong and we'll see when some electric professionals weigh in.
Charles
Charles
TheToolMan
Well-known member
I agree with charles put the 50 amp connector on the compressor and you can still use your welder,
You need to have some kind of over load protection for the compressor motor. If you go to like a 7.5 HP motor that requires a "starter" then the over load would be in the starter heaters. Smaller motors are typically "thermally protected" with a reset button. Having a plug rated for 50 amps on a 30 amp draw device would actually be desirable. And if you do go so large on your compressor that it requires a starter Elroy would recommend a "NEMA" starter as compared to an "IEC" style.
Regardless of which way you go make sure there is adequate motor protection.
Regardless of which way you go make sure there is adequate motor protection.
Not 100% sure, but the code may also call for some type of "disconnect". Someone more verse in the code would need to confirm if a plug and receptacle would be acceptable and/or if a disconnect would be required.
Elroy would suggest you do the research and "do it right".
Elroy would suggest you do the research and "do it right".
I am going by memory, but if the device is not within line of vision of the breaker there needs to be a plug or switch disconnect. It may be dated but we looked it up for plugs on 220 compressors and welders that move from plug in to plug in. Wired so only one device can be active on one circuit at a time.
I just looked inside the service panel, and it looks like the electrician used a 30-amp breaker for both the welder and the compresser outlets. Even though he used a 50-amp outlet for the welder and 30-amp outlet for the compressor. By the way, the breakers are within line of sight of both outlets. I guess I'm ok for the compressor, as long as I change the plug on it. Sounds like the only problem I might have is tripping the breaker if I have a greater than 30 amp load on the welder. Does that sound right?
Charles (in GA)
Well-known member
After doing some code book reading, I'll retract statements I made in my earlier post.
NEC 430.42 "Motors on General Purpose Branch Circuits" {which I think this is, since it is intended for more than one purpose........} overload protection for motor used on General-purpose branch circuits as permitted in Article 210 shall be provided as specified in 430.42 (A),(B),(C),(D).......
"(B) "Over One Horsepower. Motors of ratings larger than specified in 430.53 (A) {and that is motors not over 1 horsepower} shall be permitted to be connected to a general-purpose branch circuits only where each motor is protected by overload protection selected to protect the motor as specified in 430.32. Both the controller and the motor overload device shall be approved for group installation with the short-circuit and ground-fault protective device selected in accordance with 430.53"
(C) "Cord-and-Plug Connected. Where a motor is connected to a branch circuit by means of an attachment plug and receptacle and individual overload protection is omitted as provided in 430.42(A) {motors not over one horsepower} the rating of the attachment plug and receptacle shall not exceed 15 amps at 125 volts or 250 volts. Where individual overload protection is required as provided in 430.42(B) {motors over one horsepower] for a motor or motor-operated appliance that is attached to the branch circuit thru an attachment plug and receptacle, the overload device shall be an integral part of the motor or of the appliance. The rating of the attachment plug and receptacle shall determine th rating of the circuit to which the motor may be connected , as provided in Article 210."
So the compressor will have to have an overload protective device built right in. This could be a motor starter box with a thermal heating element overload device in it. or it could be a box with circuit breakers, but something must be there.
Charles
NEC 430.42 "Motors on General Purpose Branch Circuits" {which I think this is, since it is intended for more than one purpose........} overload protection for motor used on General-purpose branch circuits as permitted in Article 210 shall be provided as specified in 430.42 (A),(B),(C),(D).......
"(B) "Over One Horsepower. Motors of ratings larger than specified in 430.53 (A) {and that is motors not over 1 horsepower} shall be permitted to be connected to a general-purpose branch circuits only where each motor is protected by overload protection selected to protect the motor as specified in 430.32. Both the controller and the motor overload device shall be approved for group installation with the short-circuit and ground-fault protective device selected in accordance with 430.53"
(C) "Cord-and-Plug Connected. Where a motor is connected to a branch circuit by means of an attachment plug and receptacle and individual overload protection is omitted as provided in 430.42(A) {motors not over one horsepower} the rating of the attachment plug and receptacle shall not exceed 15 amps at 125 volts or 250 volts. Where individual overload protection is required as provided in 430.42(B) {motors over one horsepower] for a motor or motor-operated appliance that is attached to the branch circuit thru an attachment plug and receptacle, the overload device shall be an integral part of the motor or of the appliance. The rating of the attachment plug and receptacle shall determine th rating of the circuit to which the motor may be connected , as provided in Article 210."
So the compressor will have to have an overload protective device built right in. This could be a motor starter box with a thermal heating element overload device in it. or it could be a box with circuit breakers, but something must be there.
Charles
Charles was this for the device that connects to the circuit vs. the circuit itself?
Both are part of the code and have to be looked at together. I think this is the device part that makes sure that you do not heat fry something and cause a fire if you hook up to a a larger circuit that the device. ie that smaller 20 amp compressor on a 50 amp breaker that does not trip.
Another thing was that the motor itself could have the device. ie if you see a reset button on it (all of our newer ones have one), it qualified. It did not have to be a box with circuit breakers or or the starter box.
But this is a good piece of advice that I have not seen discussed here especially for people with devices with older motors over 1 hp.
Both are part of the code and have to be looked at together. I think this is the device part that makes sure that you do not heat fry something and cause a fire if you hook up to a a larger circuit that the device. ie that smaller 20 amp compressor on a 50 amp breaker that does not trip.
Another thing was that the motor itself could have the device. ie if you see a reset button on it (all of our newer ones have one), it qualified. It did not have to be a box with circuit breakers or or the starter box.
But this is a good piece of advice that I have not seen discussed here especially for people with devices with older motors over 1 hp.
TheToolMan
Well-known member
most compressors will have the overload built in to it. My quincy does and in pretty sure a I.R. will as well
Atlascycle
Well-known member
You need to have some kind of over load protection for the compressor motor. If you go to like a 7.5 HP motor that requires a "starter" then the over load would be in the starter heaters. Smaller motors are typically "thermally protected" with a reset button. Having a plug rated for 50 amps on a 30 amp draw device would actually be desirable. And if you do go so large on your compressor that it requires a starter Elroy would recommend a "NEMA" starter as compared to an "IEC" style.
Regardless of which way you go make sure there is adequate motor protection.
there is nothing wrong with an IEC starter. They are more flexible in that the overload relay will be adjustable, you will not have to purchase new heaters if you are an amp of on the sizing of the starter. They are also a smaller form factor.