240 volt service

[James P. Javery]

I'm considering setting up a 240 volt appliance in my garage and I need to determine whether it is being supplied with 220-240 volt service. The breaker box in the garage has three wires coming in from elsewhere in the building, one white wired to the neutral bus bar and two black wired to a 70 amp double pole breaker.

1. multimeter shows ~116 volts from hot to neutral for each of the two poles on the main breaker
2. multimeter shows 0 volts from hot to hot between the two poles on the main breaker
3. multimeter shows 0 ohms resistance between from hot to hot between the two poles on the main breaker

Am I not testing this properly, or is it possible that my garage is not wired for "three wire single phase" as I suppose electricians prefer to call it? My understanding would lead me to believe that the two hot wires are connected upstream to the same half of my building's electrical supply, so I'm only getting 120 in my garage despite the two hot wires.

Any ideas? Are there any other tests I can perform to verify or invalidate my conclusions? Thanks for any help you may provide...

-James

[Greg]

You have both "hots" on the same phase. Go back to the main panel and figure out why.

[Mad Mac]

[zxcvbob]

Also, the breaker box in the garage should have 4 wires coming into it, since it's being fed as a subpanel from another panel elsewhere in the building. If it were a detached garage, you could use the grounded wire as a neutral and make a new ground.

In your case, with only 3 wires, you need to tape the ends of the wire green and you don't have a neutral. It would be best not to have a breaker box in the garage (and just hardwire the appliance) if you do this, because someday someone will want to hook up a 120V circuit and try to use thata ground for a neutral connection.

Bob

[Dan]

Sounds like your double pole breaker feeding the garage needs to be moved one position. It is apparently connected to the same phase on both sides. Some panels will let that happen, some are keyed so it won't.

Dan

[newsgroups01REMOVEME]

Are you allowed to re-identify a wire as an equipment grounding conductor?

The question I would ask, what type of cable is feeding the subpanel, is it AC or is it all EMT, since he mentions no specific ground.

As for the 0 volts accross both ungrounded bars, I'm sensing this was a 'home owner' installation, and caution needs to be taken by this homeowner in trouble shooting and fixing to get 240 volt properly supplied.

IMHO,

tom @ FreelancingProjects.com

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