220V Outlet question

[john6221]

While looking at my electrical panel, I discovered something interesting. I was initially interested in seeing if I had enough slots to run 220V to my garage, but it appears that it might be done for me already...maybe....

Here's what I saw: In the electrical panel, there is a double-pole, 30A breaker. Two single copper wires are running out, through the panel's knock-out, into rigid electrical tubing. In addition, a white wire is also running into the rigid tubing and connected to the main neutral bus bar on the other end. No ground wire. These are all single wires and not NM sheathed cable.

The rigid tubing runs across the crawlspace and into my garage wall into an outlet box. I opened the box and found a standard 120V outlet. One of the black wires connected to one side, and the white neutral wire connected to the other. The additional black copper wire is capped with a nut.

I don't understand why someone would have gone to the trouble of installing the 30A double-pole fuse, running the 10 gauge copper wire, and then just hooking it up to a standard outlet.

So, my question is, can I easily convert it to 220V by just installing the proper receptacle? Do I need to run a ground wire? Something else I'm missing?

Thanks.

[Drifterrider]

I am not an electrician.

Having said that, you could hook up a 220V outlet, plug something in and see if it either a.  starts a fire.   b.  brakes the thing you plugged in.  c.  trips the breaker.

OR.....  You could get an electrician over to tell you.  If by "double pole" you mean two 30A breakers are hooked together (so that they both move at the same time), it is probably a 220V circuit.

I'd go with an electrician.  Plus, it is real hard to see your circuit box through this computer.

[SwordGuy]

It's perfectly possible to hook up a 220v circuit to what looks like a regular outlet.

I learned that the hard way - didn't know it was 220v!

Get a circuit tester.  They don't cost much and then you'll know for sure what's at each end.

[paddedhat]

I am an electrician. What you have here is the result of two different occurrences. First, somebody ran 220 to the garage, and either used it for a purpose, like they had a welding receptacle installed, and took it with the welder, when they moved, or they never completed the 220 circuit. At some point a 120 volt, 15 or 20 amp receptacle was added to the box. It is an illegal install at the moment, as the receptacle (15 or 20 amp, 120 volt ) is protected by an over-current device (30 amp breaker) that exceed the device rating.

The good news is that you have 95% of the work already completed to install a new 220 volt receptacle in the garage. First, it is legal to count the metallic conduit as a ground. I don't like it, and I do not do work like that, but it is acceptable to the current electrical code, in most areas. The one thing you have to ground however, is the receptacle to the box. This involves a short piece of #10 wire from the ground screw of the receptacle to the ground screw of the junction box. You will most likely be using a metal box cover with a hole in it to fit your new receptacle. Once you install everything it appears that the metal strap of the receptacle, the metal cover of the box and the metal junction box should provide an adequate ground, but they do not, and the ground jumper wire is required. Remember, the new receptacle cannot be rated for more than 30 amps.

 BTW, you didn't say, but on the slight chance that you are providing a 30 amp receptacle for an RV, they are not 220 Volt, they are 30 amps at 120 Volts. It's an easy mistake to make, and the RV forums frequently have tales of woe from DIYers, who destroyed every electrical part of their camper because they thought the big heavy cord, and huge plug from the RV simply must be 220 volts. (sadly enough, there are plenty of tales of idiot electricians who do exactly the same thing, and destroy their customer's RVs)

[john6221]

Paddedhat, thank you very much for the reply! I'm an electrical engineer, but not an electrician, so I just wasn't sure if I was missing something. I don't deal with high voltage at work, so I appreciate your detailed response.

My plans for the outlet are either a table saw or dust collector. Not sure which one I want to upgrade first!

[john6221]

Paddedhat, one more question. Can I wire more than one outlet to the circuit?

[paddedhat]

Paddedhat, one more question. Can I wire more than one outlet to the circuit?

Sure with the understanding that you may not be able to run both machines at once. Unless, one or both, are equipped with soft start capacitors, the inrush starting current, (FLA, locked rotor amps) may trip the breaker if one machine starts while the other is running. That said, without reading nameplates on the tools, I'm just posting hypotheticals here. There is no harm in trying, and it's probably a pretty easy job to add an additional 220v circuit in the conduit, assuming it's at least 3/4" trade size.

[zolotiyeruki]

Paddedhat, another question for you, on the topic of grounding.  I have the misfortune of living in NE Illinois, where EMT is required for residential installations. I've done a fair bit of electrical work around the house (replacing outlets, adding outlets, rewiring outlets, adding light fixtures, etc), and I have yet to see a ground wire from an outlet to the box.  I think the assumption is that the outlet is grounded via the 6-32 screws that secure it to the metal outlet box.  Stupid and ineffective, but so is the requirement to use EMT in houses.

[paddedhat]

Yea, apparently your area may be the last place on planet earth that gives up on conduit in single family homes. It's actually stupefying to talk to Chicago area electricians who truly believes that Romex is inferior, and dangerous. The trillions of feet of it, safely in use everywhere else, must be just a statistical anomaly.

Bottom line in your case is that the conduit IS the ground, and your receptacle is grounded by the back strap, which is the metal strap that has the screws and "mouse ears" on each end. If you look carefully, you can usually see how the ground contact inside the receptacle is mechanically bonded to the strap.

Now this differs from the information earlier on the thread, about needing a ground tail from a receptacle to the box. In that case, the larger receptacle will probably be installed in a 4" square junction box. The cover plate is called a raised cover, and it will have the receptacle physically attached to it (not the box) before it's secured to the wall. The code requirement is based on the theory that the receptacle and metal cover could work loose from the box, and compromise the ground.  What's the difference between what I wrote and your standard receptacles, which could also come loose? Not much, IMHO.  In your renovations and repairs, you could easily add ground tails to any receptacle you replace. They can be purchased pre-made with a ground screw already attached to one end of an 8" piece of green #12 wire. They are available in solid or stranded wire. I have even used stranded ones with the ground screw already inserted in a ring stak-on at one end, and a fork stak-on at the other. Doesn't get any easier.