compressor wiring for 220V

Not sure if this counts as GRM or if it's off topic. Oh well.

I am wiring my garage for 220V in one outlet for the compressor to paint.

I have the spots, the wire, the outlet.

I think I need a cable clamp for the circuit breaker box.

I am not certain if I need a switch or not.

What say you?

Also, I understand the procedure to be the following:

Turn off house.
Cover incoming leads with cardboard.
Do not die.
Add in 220 breaker.
Do not die.
Pop out knockout thingie.
Run wire in, put on cable clamp, run wire.
Do not die.
Close up box.
Enjoy life not being dead.

Yeah?

Hmm.. You sound uncomfortable with Electricity..

This isn't to bad of work and really if your smart not all that dangerous. Remember running in the box right next to each other is 110+, 110-, and 0 volt cables and they live happily with no arcing all the time. Unless you go poking at things with metal sticks and cut the insulation You will be ok.

Depending on the type of breaker most of them you just push in. There isn't really a Clamp the cover holds it in place. It sounds like you have the just of it. You want to run 8-10 Gauge 3 conductor wire (Assuming your wireing it up with a 3 prong welder type plug and not 4 wire oven type then you want 4 conductors). Hook up the Nuetral first then the 110 high and 110 low. Hook up your outlet and then Bam flip the breaker and enjoy the power of 220Volts.

nocones wrote: There isn't really a Clamp the cover holds it in place.

Isn't there some sort of thing that clamps the cable to the breaker box?

nocones wrote: Hmm.. You sound uncomfortable with Electricity..

Umm... yeah... I generally work on panels live (just because I'm installing new breakers doesn't mean SWMBO can do without her Netflix for 15 minutes... plus I hate working by flashlight), but I design this stuff every day so I'm pretty familiar with what electricity can do and can't do and have a healthy respect for it.

Without knowing exactly what size breaker you're installing it's hard to give much more advice other than your outline is basically correct.

tuna55 wrote:

nocones wrote: There isn't really a Clamp the cover holds it in place.

Isn't there some sort of thing that clamps the cable to the breaker box?

Yes, these:

http://www.fleetfarm.com/detail/halex-3-8-in-clamp-connector-for-nm-cable/0000000071912?utm_source=googleps&utm_medium=shopping%2Bsearch&utm_campaign=google%2Bproduct%20search&gclid=CPCUqNjRgbcCFYyi4AodHlwAUg

(random google search).

Again, need to know what size breaker to size the wire and say what size clamp you'll need.

Oh yeah that cable clamp. I thought he meant clamp to hold the breaker to the box.

I to am guilty of working on boxes live. If you don't touch the bits with power on them you can't get shocked I swear.

Ian F wrote: Again, need to know what size breaker to size the wire and say what size clamp you'll need.

I see. I'll get the wire size tonight. Does the size of the knockout in the box vary at all? What's the best way to run a wire up and out of the box up an exterior wall into the attic?

Do I need a switch, or just plug it in? What kind of switch?

There should be a switch on the compressor, just wire your plug on and plug it in. Everyone I've ever seen is just wired up to the panel no outlet no switch.

tuna55 wrote: I see. I'll get the wire size tonight. Does the size of the knockout in the box vary at all? What's the best way to run a wire up and out of the box up an exterior wall into the attic? Do I need a switch, or just plug it in? What kind of switch?

There are usually multiple knock-outs in the panel. Typcially a bunch of 1/2" (most common for residential wiring) and a handful of "multi-sized" ones that are concentric circles and you remove only the ones you need. These are usually larger.

Switch or plug will depend on the breaker size. A wall receptacle is better if you can get one, although you'll have to install a corresponding cord/plug on the compressor.

Running the wire will depend on your situation, but in a nutshell it needs to be protected and not exposed to potential damage (unlike all of the existing wiring in my garage...).

moparman76_69 wrote: There should be a switch on the compressor, just wire your plug on and plug it in. Everyone I've ever seen is just wired up to the panel no outlet no switch.

You can do that if the compressor and panel are within line-of-sight. Otherwise it's illegal as there needs to be a means of disconnecting the power at the compressor, either via a locking disconnect switch or a receptacle & plug.

I've just done this, and will share what I did both for the OP to hear and for the folks above who are clearly more pro-grade than myself with the electrons and copper can point out anything I did wrong so he gets that, too...

One of the first things I learned is that there are more types of breakers than I would have thought out there (e.g. mine are Square D "type QO"; you get different types even within one manufacturer.

Anyhow, My compressor lives about eight feet from my panel along a cinder block wall, so my life was made easy there.

I used armored cable (I think the common name 'BX' is actually a particular brand's name for it) which I got with wire already inside. It was 3/8" flex armor housing with 12 gauge wire (this is a 20-amp circuit). Two conductors plus ground. My compressor had a clamp meant to accept the bare BX housing without a clamp at that end, pretty much like this:, so I just inserted an anti-short/anti-cut plastic sleeve into that end before wiring it into the compressor's switch.

At the panel end, I used a clamp like this, which fits into a knockout in the panel, and threads into the BX armor's "threads":

I tend to do like the OP and shut the power to the box completely off back inside the house (and tape over that breaker). While I know you can do this safely without doing that, I don't have the visual familiarity inside a breaker panel that I do under the hood of a car. So while after much reading I'm about as confident as I get (I maintain a certain amount of worry about everything in life ) that everything is wired correctly, I just prefer not to be worrying about what I touch while I'm working in there while I'm also double-checking that I've got everything wired correctly. Mine's a 240V compressor, so black and white go to the breaker, and ground goes to the ground bar.

After doing the roofing last year with two fluorescent lights, the boom box, and my old 120 compressor all on the one 15A 120V circuit in the shop which would trip most times the compressor kicked on, it was immensely satisfying to fire up the compressor and notice that the lights didn't even dim one whit.

EDIT, addenda (also I just corrected all my 110/220 references to 120/240...):

The screw-into-the-armored-cable knockout adapter struck me as the cleanest, and I'd probably continue to use them. That said, they can be kind of a pain to get started, and the external-clamping variety might be easier to deal with.

I don't know about other breaker types, but the QO have two sort of sprung clamps per slot on their bases. By "per slot" I'm referring to how a single-pole breaker for 120V takes up on slot while a 240V takes up two spots). One per slot clamps onto the a power source, the other is just a clip onto plastic to locate the breaker. I imagine that this differs from type to type to some extent. These just press into place and pull off...

This is not a particularity difficult task, however, there is a lot of mix-and match confusion to be dealt with.

Some pictures of the panel, proposed breaker, wire and terminal hardware would be good so that you don't get confusing answers.

Need a load rating on the compressor. Distance from panel. Proposed routing from panel to outlet. (Gotta protect the wire)

I will warn you from experience that ignoring electrical codes can come back to bite you when you go to sell the house or have work done that requires an electrical inspection.

Overall, you seem to have the gist of this. I approve of the power-off approach. And whats with the cardboard?

NOHOME wrote: Some pictures of the panel, proposed breaker, wire and terminal hardware would be good so that you don't get confusing answers. Need a load rating on the compressor. Distance from panel. Proposed routing from panel to outlet.

Will get tonight

NOHOME wrote: (Gotta protect the wire)

Didn't know this. Some sort of conduit or the flexible stuff?

NOHOME wrote: And whats with the cardboard?

Aren't there leads leading to the main breaker that will still be live after tripping it? Aren't they right near the top of the box where I the new wire through? The cardboard was to cover the leads.

If you are thinking of doing this in a live box I would suggest you use an electric meter to find out where the sparky parts are. If you aren't familiar with the process I would suggest you kill the power and verify it is dead with an electric meter before starting work.

I recommend only working inside the box with the main power off. You can do 90% of the setup work outside the box beforehand, so you only have to have it off for a few minutes. Some people work hot all the time and get away with it, but there's no reason to cut corners.

edit: can we assume the garage is attached to the house? If it's a separate structure, there's potentially more to whole process than just running another wire.

Suggestion for the design: don't hard-wire the compressor, but plug it into an outlet. Gives you the flexibility to run a welder in the future. Even better, put in two 220v outlets so you can run a plasma cutter or you don't have to unplug the welder to run the compressor.

Keith Tanner wrote: Suggestion for the design: don't hard-wire the compressor, but plug it into an outlet.

tuna55 wrote: I am wiring my garage for 220V in one outlet for the compressor to paint. I have the spots, the wire, the outlet.

Sounds like he has that covered.

D'oh, my bad. Still, two outlets

May want to have a pro do it if you are not comfortable. Also you may want to see if your home owners insurance will be void if you DIY it. Electricity and Gas are the two things that the home owners carriers get squiffy about not having a licensed pro installing things.

In reply to tuna55:

Yes, but depending on the age of the panel the terminals to the main breaker may be covered. To be honest, I wouldn't bother with it. It's not really a good insulator and if you do happen to ground the wire it could turn into a flaming piece of cardboard. Not good. If you can find a stiff piece of plastic that would be better.

Assume all wires are live. Assume anything metal other than the box itself is live.

Still, you can never be too careful. During the renovation, I've been in the main panel more times than I can remember. At one point I was nonchalantly routing wires in the panel less than an inch from the main and I said to myself, "I'm getting way to comfortable doing this..." and made a point of paying attention to what I was doing a little better.

Here is the run I'll have to make from the panel to the compressor. Up into the attic, down into the wall in front of the compressor.

Here is the cable (can this go through the wall as-is, or do I need a sheathing of some sort?)

The new breaker

The open box

The knockouts (how do I knock these out in a low-impact, not-likely-to-drop-metal-things-on-electricity way?)

The outlet

The plug

Does that help?

I don't think that wall is insulated, being in the unheated/uncooled garage

Thanks

So, what's the problem? Just follow what you have there and do likewise. Turn off the power to that panel, make sure the power is off. Punch out the knock out with a hammer, screwdriver and some pliers. Put the breaker in the panel. Knock out the panel cover where the breaker goes. Run 220V Romex where you want it, put the new plug in a junction box by the compressor. Turn the power back on. Oh yeah, DON'T KILL YOURSELF.

Forgot about the romex. Comes with its own cladding.

Good stuff regardless if you run it in or outside of the wall or attic space.

I think you have the gist of this.