Multiwire circuit or just 240?

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  #1  
Old 04-16-07, 06:13 PM
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Multiwire circuit or just 240?

I'm going to try my best to describe this situation. I thought I understood that it was just a 240 VAC circuit but now I'm not sure. Backgroung: 1970s house, all copper wire (all 12/2+g) except AL 6/3 for some major appliances, I moved in about a year ago.

I have two twin breakers in the lower left corner of my panel. From top to bottom they are wired Black, White, Black, then White, all with 12/2+g (the whites were not reidentified). I put a multimeter on all of them and it showed 120 VAC at each connection. The top B and bottom W are the same cable and the middle W and B are the same cable. I assumed this was to provide 240 VAC to some underfloor heating I have in the bathrooms. However, I turned them off only to discover my refridgerator in the spare room when off. It is plugged into a standard 120VAC receptacle. Is it possible that someone pulled a neutral from somewhere else (again these are both 12/2+g)? Is this acceptable?


I'm going to investigate somemore!
Thanks,
Guy
 
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  #2  
Old 04-16-07, 06:29 PM
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When you say "twin" breakers are you talking double pole breakers or the tandem single pole variety?

roger
 
  #3  
Old 04-16-07, 06:41 PM
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Tandem single pole - two independant switches/breakers each with their own connection point for the outgoing wire in a single molded body. I have not removed the breaker yet from the panel.

I did, however try turning them all off one at a time and found a near by 120 VAC receptacles that turned off when I did. Of the four (again, B, W, B, W top to bottom) only turning off the bottom W removed power from the receptacle (again, the top B and bottom W are of the same cable. That eliminated my theory that there was (for some reason) a transformer somewhere knocking the voltage down.

Once I had the power disconnected to the receptacles, I removed it from the box and found two 12/2+g wires. Both the blacks were on the hot side and the whites on the neutral side...it was wired like a standard feedthrough receptacle would be wired. Again, it was the bottom W that I turned off to disconnect power from this outlet. (Of course when I put it back in the box and flipped the breaker back on it tripped out, so I have to open it again, because I 'm pretty sure I shorted it to the box...ooops).

Any thoughts?!?!
Thanks,
Guy
 
  #4  
Old 04-16-07, 06:58 PM
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This already sounded unusual when you said that the house is wired with all 12-gauge wire. But your description of these breakers sounds very unusual.

I would like more detail about your voltage readings. Let's call those four wires B1, W2, B2, W1, top to bottom. If I understood you correctly, B1 and W1 are from the same cable, and B2 and W2 are from a second cable. Is this correct?

You said, "I put a multimeter on all of them and it showed 120 VAC at each connection." All voltage measurements are taken between TWO points. To get any meaning out of a voltage reading, it is essential to identify BOTH points that you used for the reading. Otherwise, the information is meaningless.

What is the voltage between each wire and the grounding bar in the panel? What is the voltage between B1 & W2? Between B1 & W1? Between B2 & W2? And between B2 & W1?

For these two cables (#1 and #2), what wires do they contain? You said that they contain a black and a white. Do they also contain a bare wire? Anything else?
 
  #5  
Old 04-16-07, 07:32 PM
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Somebody improperly used at least one of these cables for a multi-wire circuit.

I am betting that somewhere you will find a junction box that has the black and white used as the hots and the ground used as the neutral and ground for what then becomes two circuits. The other cable may be the same, or it may actually be used as a 240 volt circuit.

It's also possible you have a combination of the two on a single circuit, which would be really bad.

I suggest that you determine exactly what loses power when you turn off these breakers one at a time, and then determine if the ground wire is in fact being used as a neutral.
 
  #6  
Old 04-16-07, 07:45 PM
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Yes, I meant they were all 120VAC above ground. Here are the Voltages:

B1 - G = 120 VAC
B1 - W2 = 0 VAC
B1 - B2 = 240 VAC
B1 - W1 = 240 VAC

W2 - B1 = 0 VAC
W2 - G = 120 VAC
W2 - B2 = 240 VAC
W2 - W1 = 240 VAC

B2 - B1 = 240 VAC
B2 - W2 = 240 VAC
B2 - G = 120VAC
B2 - W1 = 0 VAC

W1 - B1 = 240 VAC
W1 - W2 = 240 VAC
W1 - B2 = 0 VAC
W1 - G = 120VAC

Both cables are 12/2+g (just a black wire, white wire, and bare ground connected to neutral bar - that was going to be another question that is perhaps related, they seem to have used the neutral and ground bars of the panel interchangably, ie both white wires and bare wires connected on both bars, is that correct?).

I also used the connectivity function of the multimeter and found that the neutral and the ground of this receptacle I opened (which is about 3 ft from the panel) have connectivity with the ground of the panel. I also found that the black hot wires of this receptacle had connectivity with W1 (the breaker I used to disconnect power from the receptacle).

I hope that gives more details. About the whole house being wired with 12/2+g, except for special circuits (ie oven/cooktop/AC) I have yet to encounter anything but 12/2+g. I did some more looking around tonight, and that is still the case.

I also, perhaps I should mention this "spare" room used to be a garage, but has been finished off. I believe these receptacles were installed as it was finished and are not original (I could be wrong, but I think they are located where the garage door was).

Thanks for the assistance,
Guy
 
  #7  
Old 04-16-07, 07:48 PM
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Would it be possible to put a current meter on the bare ground to determine if that is being used as a neutral?
 
  #8  
Old 04-16-07, 08:04 PM
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Yes, Bob's diagnosis is unfortunately correct. This is a really bad situation you have. The person who wired this had absolutely no regard for minimum safety standards.

Correcting this hazard is a job for a professional, or at least a very electrically skilled DIYer. If this isn't you, call an electrician. It cannot be corrected merely by rearranging wires. If it could, it would not have been done in the first place. The person who wired this cheated big time in order to avoid running more cable.

And no, you cannot do any tests with your multimeter to see if the ground is being used as a neutral. And the test isn't necessary anyway. We already know it is.
 
  #9  
Old 04-17-07, 07:29 AM
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Well I feel REALLY good now that I know I've had a refrigerator plugged into one of these outlets and have run a 15 amp saw off another one. I'm planning to rennovate this room in the near future, so will probably discontinue use of these outlets until that time. Then I will probably be removing all the wallboard and will have a goo idea what is going on. In the mean time, I may see if I can find that junction box and completely disconnect these outlets.

About my other question, is there a problem with using both the neutral and the ground bars in the panel for both purposes? Both bars are located at the top of the box, the neutral (connected to the incoming White from the meter) is on the left and the ground (connected to a bare AL) on the right. Both sides have bare grounds and white neutrals connected to the bars.

Thanks,
Guy
 

Last edited by 4thisguy; 04-17-07 at 07:29 AM. Reason: Typos
  #10  
Old 04-17-07, 08:13 AM
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In the panel housing your main disconnect, the neutral bar and grounding bar are electrically bonded and can be used interchangeably. Not true in subpanels.
 
  #11  
Old 04-17-07, 08:21 AM
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Note that to be legal all splices in cables must be inside junction boxes. Further these junction boxes must be permanently accessible. Permanently accessible means NOT inside walls.

Already knowing that these splices are incorrect and dangerous, I have little faith that they are in a properly placed and accessible junction box, but that would be how I would look first. Look for a blank cover on a wall somewhere, and then look in the box behind it. Also check in each and every box that gets power from either of these breakers.
 
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