Unusual event

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L1 to L2 around 80V L1 to N - 127V L2 to N - 11V

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It's the same at the air as the dryer? Are these breakers new or existing? are they full sized breakers or mini breakers?

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Same at both.
Full size breakers. Both are working perfectly. Each breaker is about 5 years old (after a heavy up).

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Are the cables that go from the breakers to the dryer and airconditioner continuous, or are there junction boxes

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In theory, continuous, but they were laid 40 years ago, and I cannot see exactly where they go.
Note that they were working perfectly until about a week ago, and simultaneously failed.

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It sounds like you lost one leg of each cable, but I can't imagine how that could have happened. At this point you'd need to disconnect each cable from the breaker and at the load end, and do a continuity test to verify each conductor

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Already done, and there is continuity, but the power down the "bad" leg is bad.
I'll tear apart the wall near where the electrician ran the new wire, and see if he possibly nicked both of the lines.

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Even if he cut 99 percent through a wire, you'd still get a full voltage reading . The dryer or airconditioner wouldn't work, but the no load reading would indicate full voltage. The most puzzling thing is that its affecting two independent cables and breakers. In the real world, that just doesn't happen. let us know what you find. Good luck

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Have you measured the voltage at the output of the breakers, in the breaker box, when the AC and dryer are attempting to run?
Are the bad voltages you've given us at the receptacles? Or somewhere else nearby? And are they when the AC and dryer are attempting to run, or when they are OFF?

They may be, but it bothers me that you keep saying they are both wroking perfectly. AFAICT, all you have done is measure the voltage at the output end of the breakers. There is more to working perfectly than that. Like, Do they both trip at right current?
Not that any other problem would necessarily be related to the problem you're posting about, and not that I can help you much with it, but on principle and practice it bothers me that you keep saying they are working *perfectly*. It also makes me think you are vulnerable to missing something.
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mm wrote:

to be able to test the tripping current.
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"Take sides! Always take sides! You may sometimes be wrong - but the man
who refuses to take sides must *always* be wrong! Heaven save us from
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H wrote:

I'm betting L2 is open somewhere along its path and you're using an electronic voltmeter which is responding to a current being capacitively coupled from L1 to L2 and displaying that current as "11 volts between L2 to neutral".
Similarly, the L1 to L2 reading is low because of the open on L2 and the voltmeter is being "measured" through the high impedance of the capacitive coupling between L2 and neutral.
If it was me seeing that 11 volts between L2 and neutral, I'd stick the fingers of one hand across the voltmeter probes and watch that voltage drop to zero. But I won't advise you to do that because some nervous Nellie on this group would scream you could get "burned" is the open on L2 magically reconnected at just that point in time. <G>
Having recently celebrated my 50th college reunion, I remembered the Brit Professor who taught our sophmore course in "Rotating Electrical Machinery". We were mucking around with motors and generators and 3 phase power in the lab when he said, "You men will never become real engineers until you learn how to "take" a shock. <G>
Jeff
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Assuming the voltages were measured with an electronic VOM I'd say that L2 is open between the breaker panel and the load. Most likely your electrician cut or drilled through it.
Note that a 220/240V load doesn't care about the neutral; it only cares about L1-L2.
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keep in mind the OP says he has two double pole 40 amp breakers and two cables, one to the dryer and one to the A/C unit. Both cables show the same low voltage at the load ends. He also says a continuity test shows all conductors are continuous

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On Thu, 21 Jun 2007 16:58:30 -0400, "RBM" <rbm2(remove

I guess it's possible that the cables were one on top the another, and the electrician drilled through both of them at the same time.

Maybe he made a mistake on that somehow. Maybe some alternate path he didn't exclude.
A lof of maybes but something has to explain this strange problem.

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On Thu, 21 Jun 2007 01:50:37 +0000, H wrote:

Is that after the breakers? Sure isn't much else in you panel that could be faulty.
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Folks,
Firstly, thanks to all responders.
The problem was caused by the contractor who installed the line for the new addition. He did, in fact, slice cleanly through the two 240V lines that were behind the wall into which he drilled the hole.
The 11V, I was told by an electrician, actually means zero, since just about anything, including one's own skin, has that much electricity in it. So, despite the fact that I said continuity was tested, that was before I understood that 11V could mean zero.
The original contractor came in and repaired it, firstly by cutting a hole in the ceiling in the basement so he could see and confirm the damage, and then by going upstairs into the kitchen, cutting a hole in the wale above the problem and putting in a box in which the old lines were (presumably correctly) spliced onto a new leads to go to the breaker box.
We have A/C and a dryer again, for which my bride is extremely grateful.
H

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Glad you found it. That's pretty amazing, not to mention pretty bad luck. The other thing that I find amazing, is that someone could cut through two 40 amp lines and not know it

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What RBM said

Not only that, you didn't understand what it means to check continuity, and maybe you still don't. You don't check continuity by finding 120 volts at one end and 11 at the other. Or even by finding 120 at both ends. You check continuity by disconnecting the hot end, the end at the breaker, and disconnecting the dryer etc. at the other end, and measuring the resistance, the ohms, from one end of the wire in question to the other.
You coudl do this either by connecting two wires in the same cable at one, and measuring the resistance between the two of them at the other end. It should be zero or substantially less than an ohm. OR By running your own wire from your owhmmeter to the far end of the wire, and the other wire/test lead from your ohmmeter to the near end of the wire, and measuring the resistance. It should also be zero or at least substantially less than an ohm. If you use a continuity tester, you can find continuity if the buzzer buzzes or the light glows.
You should never have told us you tested for continuity. Especially since that statement confused people. All you did is test for voltage, and you should have told us the details of that, but not used the word continuity.
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But thanks for getting back to us. Much appreciated.
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Utterly incorrect on all counts. Please, next time learn how to use a voltmeter and ohmmeter before asking for help.
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