220v wiring in conduit

roofgoofDecember 23, 2009

I will be running a new circuit for an air compressor in my garage. The compressor uses 220 and runs at 22 amps with 41 amps starting draw. Manufacture recommends 50 amps breaker with 10 awg wire. I am going to use 8 awg wire with a disconnect at the air compressor. This system does not require a neutral. I want to run the wire in conduit. I thought that I read somehwere that you can not run only hot wires in conduit without a neutral. Does that sound right? There will be a ground run in the conduit. I have not used conduit before so any help is appreciated. I do know that there are fill levels that will dictate the condit size so I have that part covered.

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Ron Natalie

No, there's no such restriction. If your circuit requires a neutral it must be run with the hot wires (conduit or in cable), similarly with the ground. However, if you don't need the neutral, you don't need to run it ( conduit or not). Just run the three wires you need in the conduit and there should not be a problem. Never hurts to size up either the wire or the conduit. Having a heavier wire may actually be required if you're talking any distance due to voltage drop.

You don't say what kind of conduit you're running, but 3 #8's in sched 80 PVC (about the worst case) will work in 3/4. If you have to go underground to get to the garage make sure the wire is something like THWN that's rated for wet locations. You'll need one green and one color that's not white or green to do this property.

    Bookmark   December 23, 2009 at 10:24AM
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I am planning on using PVC for the conduit. The main panel is in the basement and I will run it from there through the basement, through a wall and into the garage. Total distance is about 60 feet of wire. I dont believe I will need the THWN since it is not wet. Should this be GFI protected?

    Bookmark   December 23, 2009 at 10:33AM
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"Should this be GFI protected?"

Not required and while there appears to be better filtering on newer GFCIs for motor transients nuisance tripping could still be a problem.

    Bookmark   December 23, 2009 at 1:23PM
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Ron Natalie

Sounds like you're not in a wet location. Was unclear if your garage was attached or not. As brick says, GFCI is not required here and probably not a good idea and a 50A 220V one (while available) is going to be pricey (though readily available because this is the common portable spa size).

    Bookmark   December 24, 2009 at 10:18AM
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