240V air compressor plugged into Dryer outlet.. need help


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Old 10-11-10, 01:48 PM
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240V air compressor plugged into Dryer outlet.. need help

A while back, I got a horizontal 33gallon 240V Craftsman air compressor from a friend for a great price. Only problem was that his ex-wife cut the plug off the end of the power cord.

My garage only has one 240V outlet (for the clothes dryer).. so I picked up a 3-pronged plug (to match my dryer plug) to put on the end of the power cord of the compressor. There were 3 wires on the power cord - black, white, and green. I wired the green one to the center prong, and the black and white each to the angled flat-bladed prongs on the plug. I plugged it into the outlet (after unplugging the dryer), and the compressor started for a split second and stopped. Tripped the breakers (2x30amp).. I reset the breakers and tried again.. no luck. So, we plugged the dryer back into the outlet, reset the breakers and now the dryer won't even turn on.

So, I'm guessing I toasted the 2 breakers on the 240 circuit to the garage. Is this something I can replace myself, or do I pay an arm and a leg to have a professional electrician come out?

Also - any idea why the compressor wouldn't work on that circuit? Did I wire the plug incorrectly?
 

Last edited by pcboss; 10-13-10 at 07:31 AM. Reason: corrected voltages
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Old 10-11-10, 03:12 PM
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What is the compressors amperage? Have you opened the receptacle to see if there is a loose wire? A three wire dryer receptacle doesn't usually have ground. The center pin should be neutral. You should check that that is how the receptacle was wired. Is this an attached garage with a separate line for the dryer or is there a subpanel.
 
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Old 10-11-10, 03:14 PM
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What is the rating of this compressor? Most compressor like this only run on 240v 15amp not 30.

Example:

 
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Old 10-11-10, 07:42 PM
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Is this garage is attached or detached ?? that will make a big diffrence on the codes and the correct way to do the repairs.

If this is a attached garage then you should not have major issue but check the connections at the recetpales and let us know what size conductrors it is to make sure you have correct size.

If this is detached garage then the bet is off unless you have subpanel in there the code is very specfic allow only one MWBC that it.

Most light duty 240 volt air compressor I know they are useally wired for 15 or 20 amp circuit due the motor size { Look at the amps rating you will see why }

Mine air compressor is monster compared to your due I have 15 HP driect drive { no belt } recetpating compressor and that have it own circuit { 3 Ph 480 volts } but let stick to the topic as Ray and HotinOKC saying about most common air compressor set up.

Merci,
Marc
 
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Old 10-11-10, 10:25 PM
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Here's some more info...
Here's some photos, along with shots of the specs and model number..










240Volts
6 hp 33Gal
1 phase / 14.0 amps
Model 919.152930
 
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Old 10-12-10, 06:40 AM
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No ,reason it shouldn't have worked and even less reason you would have toasted the breakers. Try turning the breakers all the way off then on. Using a multimeter, test light, or solenoid tester check across the breakers for 240 volts.

Open the receptacle and check the wiring. Tell us exactly what kind of wiring and how it is connected. Check the voltage between the neutral and each hot and check the voltage between the hots. If it is metallic conduit also check voltage to ground. Post a picture of the receptacle and a picture of the wiring.
 
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Old 10-12-10, 07:29 AM
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Originally Posted by cal_gecko View Post

..... There were 3 wires on the power cord - black, white, and green. I wired the green one to the center prong, and the black and white each to the angled flat-bladed prongs on the plug.....
3 wires Black, White and Green would suggest to me that it is 120V
3 wires Black, White and Red would suggest to me that it is 220V

I wonder why she chopped the end of the cord....
 
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Old 10-12-10, 08:39 AM
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3 wires Black, White and Green would suggest to me that it is 120V
Not necessarily in the US. Unlike Canada we do not have special colored cable for 240v. This is especially true for service cable. The name plates shown read 240v.
 
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Old 10-12-10, 09:50 PM
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Hey guys .. thought I'd post an update.. thanks for all your input.

I turned off the main breaker for the whole house tonight.. went into the garage pulled the cover off the outlet. I could see where the plug arced to the outlet (the compressor was mistakenly 'on' when I first tried to plug it in, and it sparked a bit when I tried to plug it in)... I checked the wires and they seemed to be solidly connected to each terminal.. but I gave them a little extra 'tightening' just to be sure. I then went out and looked at the breaker box to see if anything stood out to me .. nothing obvious.. at this point, I figured that if nothing obvious was wrong, I need to call an electrician. so I put the front panel back on the breaker box, plugged the dryer plug back into the outlet, and turned the main breaker back on... just for S&G's, I hit the power switch on the dryer...

and it came on.

I have no idea what was wrong.. but it's working now.

I may get brave enough to try plugging the compressor back in again this weekend.. but I will certainly make sure the power is off first... and I will inspect the terminals inside the power plug to make sure nothing is loose or shorting out...

Here's a shot of the power outlet showing the arc burns on the terminal..

 
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Old 10-12-10, 11:03 PM
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Just as a technical note that is an ungrounded outlet. I don't think connecting the green wire to the neutral (center slot) caused the problem but I don't know if the compressor is wired correctly. Since the compressor needs a grounded 15 or 20a circuit I would recommend running a new circuit. If you just want to test on the dryer circuit do not connect the ground. As I said I don't think that is it but I wouldn't push my luck but then I don't recommend using it ungrounded except for brief testing and the dryer circuit technically isn't grounded.
 
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Old 10-13-10, 07:05 AM
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Ray,

That receptacle looks like a 4 wire setup to me. I see the bare ground coming in from the bottom of the sheath and is pulled up and to the right.

Correction: 4 wire cable with a 3 wire receptacle...
 
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Old 10-13-10, 07:35 AM
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The slit insulation on the red conductor is a safety hazard and should be repaired. I would use heat shrink insulation.

I have two questions; is there a connector on that cable and is the back plate of the receptacle grounded? If not both should be corrected.

For increased safety I would change the receptacle to a 4 wire one and change the cord on the dryer to match. I would also run a circuit for the compressor.
 
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Old 10-13-10, 07:52 AM
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It looks to me that you donít have a proper dryer receptacle. A proper dryer receptacle has four prongs plug (red + black + white + bare ground) connected with a 10 AWG cable to a dual 30A 220V breaker.

Look at the back of your dryer to determine if you have an older 3 wire dryer cord (two hot wires + neutral) which is for use with ungrounded dryer receptacles or the newer 4 wire dryer cord (black, red, neutral-white and bare-green wire).

Craftsman sells their compressors both to US and Canada and I will doubt it they manufacture them differently for both markets. In Canada a cable with black / white wires indicates 120V but to be sure you could check the wiring at the box on the compressor to see if there is any wiring schematic in there or other indication to tell you the voltage of the compressor

Iím not an electrician but I believe that you have tripped the breaker because you connected the white from the compressor plug with the red or black of your receptacle
 
 

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