adding a 220 line in garage - gut check

[pnut]

Getting a 220 compressor for the garage. link:
http://www.lowes.com/lowes/lkn?action=productDetail&productId=221565-14989-LLA3706056&lpage=none

I want to add a 220 line. I have done some basic household (my own) electrical work, and did add a new line years ago, but want to make sure I'm not missing anything.

I plan to use 10ga Romex, with a 30a square D breaker. If I recall right, 220 Romex is different than 110 Romex. I will use fish tape to get the wire from the box in the basement, up an exterior wall, into the garage ceiling, and down the opposite exterior wall for an outlet (40-50 feet total length). The insulation has a paper skin on it, so that should help with the wire routing through the exterior walls.

I will turn off the main into the house and testing with my multimeter before touching anything, including routing the cable.

I plan to use a clamp for the Romex into the box, and look to the other breakers to be sure I know which color wires go where, and how to be properly routed (that is how I did it last time, it's not that complicated).


I was hoping a few people could reply with a thumbs up to make sure I am doing it right, or else tell me what I've left out.

 

[mhm993]

Make sure you mark the white which is really the second hot leg at the panel and box. On a fast read, you sound just fine.

I added a 240 line for the first time recently. I think you'll find my gj thread with similar questions and answers about the panel and breaker if you search. If I can do it.....

 

[FastEddieG]

Congrats on the new purchase. The experts will chime in, but my amateur instincts say that you will need 10-3 romex (3 wires + ground). I'm not aware of 110 vs 220 romex persay, but the number of wires in the romex does matter. You need 2 hots, a neutral and a ground, and the 10-3 would provide that.
-Ed

EDIT, based on some prior discussions I've read, the experts can direct you on the proper breaker and wire size. I've learned for circuits like this, the breaker is sized for the motor, and since the motor can draw more on startup, a larger breaker might be needed. But again, the experts will chime in.

Above all, research this thoroughly, and don't just trust text you read on the net Some things are right, and some things are wrong, but on the flip side some things are minimum code and others are overkill but still comply with code. At the end of the day safety and complying with code is primary.

 

[Zrexxer]

Congrats on the new purchase. The experts will chime in, but my amateur instincts say that you will need 10-3 romex You need 2 hots, a neutral and a ground, and the 10-3 would provide that.
-Ed

Absolutely not. 220V single phase is two hot legs and a ground... period. No neutral.

 

[Falcon67]

> If I recall right, 220 Romex is different than 110 Romex.
No, wire is wire. For an dedicated 220 air compressor motor circuit, what Zrexxer said. That's 10-2 w/ground as an example. (wire size dependent on run length and load) Mark the white on both ends - I use some red touchup paint. The white becomes your other power lead.

Actually, for that size compressor it will run on 12 ga with a 20A breaker. If you figure 3.7 HP at 80% efficiency, that works out to about 15.5A @ 220. That's right at the limit for a 20A circuit. #10 will provide an extra margin and if you upgrade later, you can likely use the same wire. I'd still fuse it at 20A.

What you might be thinking is about a regular 220V run like for a dryer. The dryer heating element only needs two hots and a ground, but the controls and motor are usually 110V so the dryer needs a neutral to provide 110 from the run. And that wire would be 10-3 w/ground for example.

 

[FastEddieG]

Absolutely not. 220V single phase is two hot legs and a ground... period. No neutral.

Again, I learn something else. Thanks! And OP, this is my point, do not trust the Internet without doing plenty of research
-Ed

 

[mrb]

Absolutely not. 220V single phase is two hot legs and a ground... period. No neutral.

nevermind....

 

[FastEddieG]

> If I recall right, 220 Romex is different than 110 Romex.
No, wire is wire. For an dedicated 220 air compressor motor circuit, what Zrexxer said. That's 10-2 w/ground as an example. (wire size dependent on run length and load) Mark the white on both ends - I use some red touchup paint. The white becomes your other power lead.

Actually, for that size compressor it will run on 12 ga with a 20A breaker. If you figure 3.7 HP at 80% efficiency, that works out to about 15.5A @ 220. #10 will provide an extra margin and if you upgrade later, you can likely use the same wire.

What you might be thinking is about a regular 220V run like for a dryer. The dryer heating element only needs two hots and a ground, but the controls and motor are usually 110V so the dryer needs a neutral to provide 110 from the run. And that wire would be 10-3 w/ground for example.

Thanks for the info. I have "subpanel wiring of the brain" right now

 

[Zrexxer]

no. 220 (240 actually) single phase is two hots, a neutral, and a ground. You can omit the neutral when supplying loads (such as a 240v compressor) that dont need it.

I'm not going to argue with you, but the neutral is the center tap from the transformer, and is only part of a circuit requiring both voltages (110/220, 115/230, 120/240, whatever you want to call nominal voltage) for appliances that use both, such as a range. Besides, if you "omit it" then it's not part of the circuit to begin with is it? So your argument is self-contradicting.

 

[Falcon67]

220, 221 - whatever it takes

Note (thinking, look out) - you will probably end up with 10-3 anyway because thats what most of the big box stores stock. Just clip the neutral - or tie it in at the panel and just ignore it on the other end.

 

[Harm]

You sound like you have the right idea.
As for 110 vs 220 I'm not sure what you mean.
To wire 10/2 for 220 volts you put the ground wire into your neutral bus in the panel and put the black and white wires into the double pole breaker. Mark the white one.
To wire 10/3 for 220 you put the ground and white wires into the neutral bus and the put the black and red wires into the double pole breaker. No marking.
My compressor is similar to yours, wired with 12/2 on 20amps into a 4-prong dryer receptacle. Incidentally, I've never once tripped the breaker.
The white wire is optional for your install. So, take a look at the receptacle you want to use. If you go 10/2, the ground wire connects to receptacle's neutral. If you go 10/3 the white wire is the neutral and the ground is the ground. Also, take a look in the junction box on your compressor itself. Mine has connections for 2 hots, a neutral, and a ground. However, the ground screw was too close to something to accept the washer style ground connecter my plug whip came with. I had to switch to a horseshoe type.

I suggest getting an extra-deep 2-gang plastic box. Dryer receptacles are fairly deep and 10-wire is harder to persuade into a box than thinner stuff. You may have to pre-bend the wires. Also, be sure to look at your plug before mounting the receptacle. In my experience, if you can read "leviton" right side up then your plug won't hang right.
Falcon is right twice, imo. Firstly, 30 amps is a bit overkill for your application and secondly 10-wire is a specialty item. You'll be overcharged per foot or you could buy way too much for you. 250ft rolls are the economical choice in my area.
*edit - If you decide 10/3, use the neutral wire on both ends. Then you'll be grounded too.

 

[mrb]

I'm not going to argue with you, but the neutral is the center tap from the transformer, and is only part of a circuit requiring both voltages (110/220, 115/230, 120/240, whatever you want to call nominal voltage) for appliances that use both, such as a range. Besides, if you "omit it" then it's not part of the circuit to begin with is it? So your argument is self-contradicting.

yeah i get your point. if it had a neutral it would be a 120/240 circuit. a 240v circuit would never have a neutral -dont know what I was thinking....

 

[84scrambler]

I would have to do some math to determine what size diameter wire you need for your given run and the associated breaker based on the current draw so I can't give you numbers on that right now.
For possible future upgrades I would get a 4 wire cord (ground, black, white, and red). I would cap off the neutral (white) and have it in place in case you would like to have the option of running a 110 at your location. Run the black to 1 side of the phase, run your red to the other side of the phase and finally run your green to earth ground. Do not run it into the neutral bus. What Harm is suggesting is not safe. If something where to happen to the neutral coming in from the utility company you would be stuck with a floating ground this is why you have your own earth ground.

 

[mrb]

You sound like you have the right idea.
As for 110 vs 220 I'm not sure what you mean.
To wire 10/2 for 220 volts you put the ground wire into your neutral bus in the panel and put the black and white wires into the double pole breaker. Mark the white one.
To wire 10/3 for 220 you put the ground and white wires into the neutral bus and the put the black and red wires into the double pole breaker. No marking.
My compressor is similar to yours, wired with 12/2 on 20amps into a 4-prong dryer receptacle. Incidentally, I've never once tripped the breaker.
The white wire is optional for your install. So, take a look at the receptacle you want to use. If you go 10/2, the ground wire connects to receptacle's neutral. If you go 10/3 the white wire is the neutral and the ground is the ground. Also, take a look in the junction box on your compressor itself. Mine has connections for 2 hots, a neutral, and a ground. However, the ground screw was too close to something to accept the washer style ground connecter my plug whip came with. I had to switch to a horseshoe type.

I suggest getting an extra-deep 2-gang plastic box. Dryer receptacles are fairly deep and 10-wire is harder to persuade into a box than thinner stuff. You may have to pre-bend the wires. Also, be sure to look at your plug before mounting the receptacle. In my experience, if you can read "leviton" right side up then your plug won't hang right.
Falcon is right twice, imo. Firstly, 30 amps is a bit overkill for your application and secondly 10-wire is a specialty item. You'll be overcharged per foot or you could buy way too much for you. 250ft rolls are the economical choice in my area.
*edit - If you decide 10/3, use the neutral wire on both ends. Then you'll be grounded too.

um most of that makes no sense. You would never put the ground on the neutral bus, unless you are in a service panel containing the N-G bond and the neutral busbar IS the grounding bus.

You would never connect the ground wire to a receptacles neutral.

 

[Aceman]

Jesus, 14 posts in this thread when one would of sufficed...

10-2 Romex on a 30 amp breaker will be fine.

 

[Motofixxer]

Hmm idk... if your wiring it now, you might wanna plan for a larger in the future. I have had the same size compressor for a while. But I'm thinking I might upgrade in the near future. So what I originally wired it for is a little on the light side for what I might put in. I used the same wiring as your planning. My drywall is not up so I am replacing it with 6ga and at least a 40amp breaker. For the difference in wire cost...it's worth it to me. And I found a 2 gang electrical box labeled for 240v. Which will give more room to work with.

 

[Steevo]

$399 for that compressor is a pretty sweet deal.

 

[pnut]

$399 for that compressor is a pretty sweet deal.

I will either be choosing that one (plus 10% off at Lowes for "moving" coupon you can get online), or the CH version they sell at HF (plus 20% off coupon I found in Car & Driver mag).

Both would be pretty good, but I'm leaning toward the Kobalt for the higher pressure limit of 155PSI.

 

[pnut]

Bought the Lowes Kobalt model.

Based on the manual, I am going with 20A and 12-2 wire.

 

[mustangmccance]

Hmm idk... if your wiring it now, you might wanna plan for a larger so I am replacing it with 6ga and at least a 40amp breaker. For the difference in wire cost...it's worth it to me. And I found a 2 gang electrical box labeled for 240v. Which will give more room to work with.

I will admit right off I am no electrical guru I always have my Dad help with the wiring, but I can't really think of a good reason to oversize your breaker. unless I am mistaken you want it to be able to run enough juice to handle your load and not much more. it seems to me that it would be smarter to put in the 20A breaker now to handle your current load and IF you upgrade later then increase the load capacity of your breaker.

as far as wire size, the larger wire will have less resistance and be able to handle larger loads later and that is certainly reasonable, if you anticipate increasing the load that much in the future.

if I am mistaken on this please explain it to me as I said I am a newb at wiring.

 

[Aceman]

Bought the Lowes Kobalt model.

Based on the manual, I am going with 20A and 12-2 wire.

For the slight increase in cost, I'd highly recommend running 10-2, even if you breaker it at 20 for now. It'll save your **** if you ever decide to upsize your compressor. All the decent sized shop compressors I've wired in have been a 30 amp circuit minimum.

 

[wineslob]

Cutler-Hammer Motor Circuit Selector sez:

3 hp single phase motor: 230V /17 amp draw. Wire is 10 ga with a 40 amp breaker.

Adjust accordingly.


What does the motor plate say?? amperage wise?