240v wiring in phase?

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  #1  
Old 11-24-14, 03:30 PM
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240v wiring in phase?

Hi there,

I've just installed an electric wall oven and am having some trouble with the wiring. I'd be really grateful if any of you have ideas.

After installing a new mini dual-pole 240v breaker and wiring in the oven, nothing happens at all--no lights go on, the panel stays dark, etc. Testing the connection at the back of the oven with a voltmeter, I read 120v across live-ground, 120v across the other live-ground, and zero volts across the two live wires (should be 240v). This suggests to me that the two live wires are in phase, rather than split-phase, and they're canceling each other to zero volts instead of adding to 240v.

The new dual-pole breaker is installed next to two other dual-pole breakers that supply my house's electric heat, which seems to be working fine, so I think the rails are functioning properly.

Any idea what's going on, and how I could fix the problem? I need the oven to make Thanksgiving dinner!
 
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Old 11-24-14, 03:58 PM
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Can you post a picture of the breaker you installed? I have a feeling you installed the wrong type. http://www.doityourself.com/forum/el...your-post.html
 
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Old 11-24-14, 04:20 PM
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Do you have a GE breaker box. What you describe is a common mistake with GE breaker boxes. If not GE then Like Larry I'd suspect you used a tandem breaker not a 2-pole breaker.
 
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Old 11-24-14, 05:21 PM
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This is indeed a GE breaker box. Photo attached; the new 240v dual-pole breaker is the bottom pair of 15 amps. How does it look to you?Name:  IMG_20141124_171456.jpg
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Old 11-24-14, 05:45 PM
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What is the amperage rating of your wall oven? I'd bet it is more like 30 amps instead of 15 amps. You don't add the amperage of the two breakers.
 
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Old 11-24-14, 05:50 PM
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Actually it's an unusually small oven; it's rated at 15A. The breaker isn't tripping, for what it's worth; it's just (I think) delivering power in phase (rather than 180 degrees out of phase) on the two 120v circuits.
 
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Old 11-24-14, 05:58 PM
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You may need to move the breaker up a half slot. I'm pretty sure you have both contacts of the breaker on the same leg. You need to move it up so the two contacts are on different legs. It will read 240 when you get it right (0 when wrong).

Suggestion remove the 20 amp single pole above it. Move the 2-pole up into that slot and put the 20 amp single pole below it.
 
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Old 11-24-14, 06:27 PM
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With both legs reading zero between them means you are only on one leg of the panel. You need to hit both legs to get 240 volts.
 
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Old 11-25-14, 12:02 PM
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Remarkably, the problem was two faulty circuit breakers in a row. The other 240v breakers were working, so we knew the rails weren't the problem, and moving the problem breaker around didn't do anything. Finally trying yet another new breaker did the trick.

Thanks for your help everyone!
 
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Old 11-25-14, 12:06 PM
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A good lesson for everyone. New doesn't mean good. It means maybe good. Thanks for posting. Your experience may help others.
 
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