Compressor wiring again

[logical]

I searched but nothing seemed to really point me in the right direction. I just ordered an eaton 3HP, 3cyl single phase, single stage, 60 gal compressor. Draws 19.5 amps @ 220V and a 30 amp breaker is reccomended...I get that part, 30 amp it is.

My question is exactly how to do it, I've done tons of 110V work, new circuits, basement remodels, lighting, etc. but never 220V dedicated circuits. My panel is just thru the wall in my basement, compressor will live in my attached garage a total of maybe 50 feet of wire from the panel.

Do I just put the 30 amp breaker in the panel...I have plenty of space and 300 amp service..and run 10 gauge (10-2 + g) wire to maybe a shut-off near the compressor. A 2 pole breaker right?

Maybe I should just ask flat out how to do this???

 

[Marty256]

I'll try to explain it the best I can. On a 110 circuit black is hot white is neutral and copper is ground. On 220 black and white are hot. That is why a 220 breaker is double wide so both white and black go onto the hot bar in the breaker box (two set screws on breaker). If you're not sure what you're doing maybe leave it to the pros. Getting hit with 220 can cause some serious damage to the nervous system.

 

[rocketman]

If it were me...I'm no certified electrician. I'd run conduit out to the compressor, put in a 2 pole 30amp breaker in your panel. 1 white with black tape to designate the second hot and the other black. You run two hots out. Pretty simple actually. I guess the white with the black tape allows you to differentiate between the 2 hots by sight.

Union guys chime in here if I'm off base!

 

[Matti]

I'm no electrician but will be running a similar set-up soon. I would look at your existing electric dryer or range breaker on the panel to see how it is done. You need to connect to 2 - 110v breakers tied together to get 220v. Codes likely prevent you from running 220v directly to your compressor in your garage from your house. I would at minimum put in a disconnect box in the garage or a sub panel. #8 would be required but I would have to check to see if #10 would do. I'll get an electrician to check things over and do the main connections at the panel!

 

[logical]

I'll try to explain it the best I can. On a 110 circuit black is hot white is neutral and copper is ground. On 220 black and white are hot. That is why a 220 breaker is double wide so both white and black go onto the hot bar in the breaker box (two set screws on breaker). If you're not sure what you're doing maybe leave it to the pros. Getting hit with 220 can cause some serious damage to the nervous system.

I know that much, I know what 220 is...that wasn't my question. I'm asking about the configuration.

 

[logical]

I'm no electrician but will be running a similar set-up soon. I would look at your existing electric dryer or range breaker on the panel to see how it is done. You need to connect to 2 - 110v breakers tied together to get 220v. Codes likely prevent you from running 220v directly to your compressor in your garage from your house. I would at minimum put in a disconnect box in the garage or a sub panel. #8 would be required but I would have to check to see if #10 would do. I'll get an electrician to check things over and do the main connections at the panel!

Well...my dryer has an outlet and a plug but runs direct from a breaker in the panel. I don't see why I shouldn't/couldn't run the 220 from a breaker to a shutoff in the garage and then hardwire to the compressor. I've been inside the panel many times...I ain't a'scared.

 

[Charles (in GA)]

Run one red wire, and one black wire off the duplex/double pole circuit breaker. Run one green ground wire off the ground bar. That is all you should need, no neutral is needed unless the motor starter is weird and needs 120V for some reason. If the compressor is more than 50 ft straight line, or is not in line of sight from the breaker panel, you must have a disconnect at the equipment. Easiest thing to use, cheapest is to go and buy a weatherproof A/C outside disconnect box, they have a switch or pull out in them, usually rated up to 60 amp and cost $10 to $12. Mount this next to the compressor and then run wire from this to the motor starter or pressure switch or wherever on the compressor. I'd really consider running #8 wire, but #10 is OK.

Charles

 

[pmiranda]

Well...my dryer has an outlet and a plug but runs direct from a breaker in the panel. I don't see why I shouldn't/couldn't run the 220 from a breaker to a shutoff in the garage and then hardwire to the compressor.

There are a couple things... I'm guessing your dryer plugs into a 220V outlet mounted in a junction box. That's the right way to do it... a flexible cord terminated in a plug, and the in-wall wiring terminated in a junction box, connected by a listed outlet properly installed.


If you want to hardwire your compressor instead of using a flexible cord plugged into an outlet, then you have to use conduit properly terminated at a junction box [edit: and properly protected and supported], such that there's no chance of anything damaging the conductors.

If you just string some unprotected Romex from the compressor into the wall, it could be damaged by animals or falling objects or even ripped out of its connection if not properly secured.

In addition to making sure the wiring itself is right, common sense (and I'd hope you local building code, usually by reference to the NEC) should tell you you must have a shutoff at the equipment location if you can't just unplug it.

I'm not a licensed electrican, but I have read the NEC and done some wiring.
If you don't have one handy, here's a nifty online version (hopefully not older than what your locality requires): 2005 NEC
Sorry I don't have chapter and verse handy, but I hope that's useful to you.

 

[flesburg]

220 is two 110s that are out of phase with each other.

There are two bus bars in your main panel. Alternating 110s on each side are from alternating phases. You just need to make sure you pick up different phases on each leg of you 220 breaker.

Then, I do not do what everyone else does. I buy 3+g 10 gauge wire for a 30 amp 220 circuit. I use black for one hot. I use red for the other hot. I use white for the neutral. I use bare copper for the ground. New code will require 4 plug devices for 220. I know that for a 220 motor, the neutral is not needed. But...

I like one red for hot. One black for hot, and the white for ground or neutral. If I use 2+g for 220, I paint the white insulation red!

A year later I can Identify what it is.....

 

[logical]

OK, thanks.....just wanted to be sure.

 

[RobRace10]

I also added a 40 amp breaker in the garage picture below. The ground and Neutral are contiguous in my main breaker box so there are only 3 wires no bare copper ground. The red and the black wires are each a 110 hot leg.

 

[W-Cummins]

I also added a 40 amp breaker in the garage picture below. The ground and Neutral are contiguous in my main breaker box so there are only 3 wires no bare copper ground. The red and the black wires are each a 110 hot leg.

There may be a problem with your install here..

I can't tell for sure but I'm assuming that the conductors here are less than 6 gauge as 40 amps is normally 8 gauge? In any case;

You don't have a EGC here unless your trying to use the white conductor as one ( and you can not use it as one unless it's 6 gauge or larger ) if it is and you are doing that, you need to mark the wire as a EGC (IF the conductor is smaller than 6 gauge you can not remark it as an EGC) NEC 250.118 a (1 and 2)

Also if you can remark the EGC it looks like you will need to install the grounding/bonding screw or run a ground to the can....

Where did you find that NMC that dosn't have a ground wire in it?? I didn't know that they still made it that way, or did you cut it off?

I guess I would go ahead and re-mark the thing even though if it's too small it will not be code current ( as I'm also assuming that it was not inspected) it will be at least clear what's going on and then ground the can too....

William....