Troubleshooting 240v


Old 02-08-13, 02:51 PM
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Troubleshooting 240v


I've been working out the garage for a few months off and on getting ready for a project I am getting ready to do. From previous experience I decided I wanted a air compressor for my needs yay! Previous resident of the house was a ASE Certified mechanic, and such he had a monster compressor in the garage the wiring is all there. Now the fun part.

Bought a multimeter to test the outlet before I drop $1000+ on a compressor and I am glad I did. After testing the DMM on 3 outlets know to work in the house without any issues went to the garage. Tested it and I am only getting 120-123 off the outlet, moving the probes around I get the error 0.0l not sure what it means I bought a somewhat cheap DMM for my needs.

First image is of the sub panel in the garage

Second image is of outlets nearest the panel the ivory ones do not work.

Third image of of the outlet believe to be the 240, the wires from the 30amp double pull lead to this socket.

#1 -

#2 -

#3 -

Now before I go any further I wanted to make sure I was testing the outlet correctly On my DMM I set the dial to the V with the ~ underneath it. Double checked 3 sources and I appear to be doing this correctly.

Now the thing that baffles me is, when I tried to shut off power to the suspected 240v outlet, the 30amp double pull do noting for it (although the wires lead directly to it). Instead the 20amp directly to the left shut off power to the outlet.

I am confused and unsure where to start searching for my issue, should also note there is a decent size exhaust fan directly behind this outlet in the garage itself. ( this is a detached garage)

I am not rush to get this solved because if I cannot safely fix this I have to pay a guy electrician to come out and solve the issue for me.

One other note the outlet is aprox. 3 ft away from breaker box.

So any input on where I should get started here, and how to proceed safetly.

Can also get any other needed information pictures ect...

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Old 02-08-13, 03:15 PM
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First post is completely irrellevant, my dad came out we chased down the wires. The 30 amp is wired to a switch which is wired to the exhaust fan.

Still have another question though, I am just thinking outloud here which isn't always good.

In my mind if I unhook the fan, completely remove it from the garage and simply rewire the outlet to the wires for a new outlet cappable of handling 240v that should work in theory correct?
Old 02-08-13, 03:52 PM
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You have 240 volts available at that double breaker and the brown wires. Depending on where your new compressor location will be, remove them from the conduit and re-conduit (I think that's a word) to a new location with an approved receptacle for 240 volts, or if the compressor has only a pigtail or whip, wire it directly into a junction box with a cover and join the wires there.
Old 02-08-13, 04:48 PM
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Thanks for the response, I am going to go ahead and have my uncle come out and explain to me the proper way to wire this up to code ect... Just wanted to make sure my thinking was sound.
Old 02-08-13, 04:52 PM
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That single receptacle in your last picture is a single 120v 20 amp receptacle.

To be a 240 volt receptacle......both slots would be horizontal.

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