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Discussion Starter · #1 ·
I need some help as to what I need to get to install a 220V outlet (i.e wire gauge / switch amps, etc) in my garage for an air compressor.

I have installed a 110 circuit so I'm not totally clueless jut snever have done the 220.
 

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220 is simply 2 110V lines. When I added 220V to my garage, I installed a sub-panel in the garage from th emain panel. I simply installed a 100A breaker in the main panel, and then ran wires from there to the sub-panel where I installed 5 220V 50A breakers, and 15 110V 30A breakers.

Go to Home Depot or Lowes, and get a book on wiring. They are very informative.

Some useful tools:

Wire cutters
Pliers
Electrician's fishing line for pulling wire through conduit

Hope this helps

2FAST
 

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Builders Lackey
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Been a while since I did it, but you will need a double-pole breaker.

Connect the red and black wire to each of the breaker terminals and the white/green wires to the neutral bus bar or ground bar.

As 2Fast said, Home Depot has a good book called "Wiring 1-2-3" that covers everything.

-Shawn
 

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Paul,

I don't mean to sound like a worry wart but...

BE EXTREMELY CAREFUL WITH 220V LINES.

Many of us have been zapped by 110 without too much problem, it can even be fun ;) ...220 will kill you. Always make sure the power is off before you do any work on those lines.

Good Luck,

Steve B
 

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OK back up.....

First you need to know the amperage rating of the double pole breakers that you need. If your compressor requires 30 amp, or 60 amp then that is what you will need to buy. You will also need the make, such as Square D, GE or whatever. For any compressor, you should use a minimum 10 gauge wire. Everyone will say 12 but Compressors have a higher starting current than most appliances do.
You will also need to make sure that you are not over-taxing your breaker box. You will need to have 2 (adjacent) empty slots for the breaker to fit into. (2 seperate poles in the breaker box are needed for the 220) If using a plug in type compressor make sure you get the locking type plug and outlet. It will keep the compressor from coming unplugged in the middle of a job. If hardwiring in a compressor make certain it is bolted down. It keeps anyone from trying to move the compressor causing the wire to pull out of the box.
Wire from the plug backwards. Never connect to the fuse panel until everything else is connected. Keeps you from zapping yourself, should you forget to turn off the breakers.
Lastly, as mentioned, there is a bar that the nuetral is connected to. However you need to consult with your local and state electrical code as to whether or not they want you to do this if using a sub-panel. Some electricians do not use this bar in a sub panel as it allows too many paths to ground and you could zap yourself while working on some other tool in the garage.

If your not sure get an electrician. Not worth burning down the house or Arc welding yourself to your bench grinder some day.

Remember....BE SAFE.



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FFCobra Craftsman
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My opinion, go with an electrician. The handyman types that do side jobs are typically cheaper. They'll take cash and come on a weekend or at night.

You could have them run the wire and install a sub-panel in your garage. And do the rest of the wiring yourself. You'll know that's done right, it's up to code and you won't find out what a nasty electrical burn is like. Wiring anything else to that box is easy as you can just turn off the main breaker for that box.

Your not wiring up your entire house, so your not going to spend much on wire. Get heavier gauge than necessary. Better to be on the safe side.

-steve in nj-
 

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FFCobra Master Craftsman
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Paul, like Steve B. said, be careful. Other than not getting shocked, the next most important thing is to make sure the wire amperage rating is more than the breaker trip setpoint. That way and you won't burn your house down.

It's not that hard, really.
 

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Take the name plate amperage off the compressor motor. Multiply this times 1.25.This is your conductor size. 20amp=12 gauge, 15amp = #14 gauge..
Example: Compressor name plate 13.8
13.8 times 1.25% =17.25...go with #12 wire.
You can use a regular romex wire for this. You would be taping the white conductor black to identify it as a hot wire and not a neutral.
Both these wires will land on the double pole breaker. The bare wire will be ground and should be landed on the ground buss.
**The name plate will base the current(amps) on 220 volts, but your house has 208, so go to the next size wire if you are within 10%.

The breaker will be a two pole large enough to protect the wire. again 20amp breaker for #12.,30amp for #10 wire.15ampfor #14 wire.
You will need a disconnect at the compressor... a double pole switch or a cord and plug(your choice)
If you are not used to working in the panel then shut it off, but remember there is still 208volts in the panel coming into your main switch.

As a electrician I've been shocked
6...6...66..66..times in da.da.da.da head.

[ January 05, 2004, 08:01 PM: Message edited by: Knightyme ]
 

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Senior Charter Member
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All good advice here, however, check local codes first. In california every county has something alittle different. For example, sub panels you have to separate the nuetrals (white) and the grounds on separate busses. And any 240v. circuits are four wire. two commons, nuetral, and ground, as in the old says the nuetral double as a groud when connected to the common buss in the service panal.(10-3 romex was used and you taped the nuetral black like above mentioned).

good luck jack stand
 

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Originally posted by jack stand:
All good advice here, however, check local codes first. In california every county has something alittle different. For example, sub panels you have to separate the nuetrals (white) and the grounds on separate busses. And any 240v. circuits are four wire. two commons, nuetral, and ground, as in the old says the nuetral double as a groud when connected to the common buss in the service panal.(10-3 romex was used and you taped the nuetral black like above mentioned).
In every state neutrals have to be isolated in subpanels.
Two neutrals, 1-ground and 2-hots are 5 wires???
No neural on that compressor.
That compressor has two hot wires and a ground.
That ground, as I mentioned must land on a ground buss. If it goes to a subpanel, then that subpanel, if wired correctly should have a separate ground buss from the neutral buss.
If going to the main breaker panel, then the ground s and neutrals are landed on the same buss.
National Electric code states that the Neutral(grounded conductor) can only be bonded to ground(grounding conductor) at the main dissconnect.

[ January 06, 2004, 07:40 AM: Message edited by: Knightyme ]
 

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Sr FFR builder
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Definately, be careful as everyone has said to this point. I feel your pain. My first real experience with wiring 220 was wiring my hot tub. :eek: Talk about a leap of faith, it took me a few minutes before I stuck my hand in the water. But now I have wired 2 tubs in two different houses and yet I am still here, imagine that. The thing that still baffles me to this day is not the 2 hot leads that make the 220, but the fact that the neutral wire ends up going to ground. I have a difficult time comprehending this concept. In other words, when you look at the box, you will see that the neutral bus is bonded to the box and to ground. Anyway, my point is that if you take your time and do your homework, you can do this project very easily. If you are too concerned about safety and are not comfortable with your level of knowledge about the topic, have an electrician do it. Good luck
 
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