MAIN BREAKER QUAGMIRE - HELP

[Strathead]

Been mentioned and I am with those - you never mentioned whether you have 240 volts between L1 and L2. If you don't the problem is definitely "upstream" from where you are trying to measure.

Tree branch rubbed through conductors of an overhead service drop sounds like it could be a possibility.

Lost neutral gives you varying voltages to neutral.
Lost ungrounded conductor will still leave you with consistent 120 volts to neutral on the good ungrounded conductor, but varying volts on the one with that has been lost - but any 240 volt loads will never see 240 volts either.

Loss of an ungrounded plus the grounded conductor leaves everything at one potential - unless you place a probe in remote earth then everything will read ~120 to that probe. Sounds like you could be headed toward this last issue as being the problem with what you have mentioned so far.

Go back and make sure you do measure L1 to L2, and also maybe measure to remote known grounded object. If all you have intact is one ungrounded conductor when your main is closed and line to neutral loads are connected - the only "return path" is going to be the grounding electrode, but it may be high enough resistance that very little volts drop across your intended loads, and the only way to measure any significant voltage is to measure to true ground that is remote from your GES.

I will answer for him. Look at the post with the pictures. He shows the L1 L2 measurement.

 

[al hildenbrand]

KWired,

Been mentioned and I am with those - you never mentioned whether you have 240 volts between L1 and L2. If you don't the problem is definitely "upstream" from where you are trying to measure.

I delved into more information. The fact that when L1-L2 I got 0 on both reads, it may be an issue with the transformer.

Looks like we're all going the same direction with our troubleshooting. KWired, look at the last two, of six, photos that are in Cybatrex' Post #16.

Cybatrex, in addition to the transformer itself, give a think to the number of wire-to-wire splices in the service conductor circuit between the LINE terminals in the Service Disconnect where the conductors from the meter socket land, and the SOURCE in the transformer secondary. Consider just one conductive path, say, L1. (1) Load meter terminal (2) Load meter jaw-to-meter-tine (3) Line meter tine-to-jaw (4) Line meter terminal (5) service L1 to overhead-drop splice (6) overhead-drop to pole-to-pole secondary wire (10) secondary wire to transformer-lead (11) transformer lead to transformer terminal (12) transformer terminal to transformer winding. (for the grounded service conductor omit the connections into and out of the meter itself, that is, omit a count of two.

L1 = 12 splices, L2 = 12 splices, and N = 10 splices, which, added together yields a total of 34 splices all of which are exposed to weather in varying degrees. Mix in heat / cool cycles (with thermal expansion / contraction) and the dirt and oils of atmospheric contaminants, and one has a lot of failure points.

 

[kwired]

I will answer for him. Look at the post with the pictures. He shows the L1 L2 measurement.

For some reason I never seen them, but they just help clarify what he did mention earlier. I still think he has lost one ungrounded conductor as well as the grounded conductor somewhere upstream. Looks like he has a meter with a low Z setting but he is not using it in any of those pictures either. I bet if it used low Z setting he would find lower if not zero readings on all tests with breaker closed.

Seen about the same thing happen before when tree branch rubbed it's way through an overhead service drop, with one ungrounded conductor being only thing left intact.

 

[al hildenbrand]

It may be that one of the lugs is touching the other somehow behind that assembly that's holding the breaker that I can't see.

Personally, I doubt that you have a bus to bus failure very much.

Here, don't forget all the loads inside the house. Unless you have gone around to every single one of them and verified that they are actually off, completely off (no TV remote controls still live, etc.), there will be load connected to the branch circuits. When those branch circuits are ON, with connected load, there is a real resistance from LINE to NEUTRAL and LINE to LINE (for 240 volt loads).

Turning on the 125 Amp Service Disconnect breaker connects the house load RESISTANCE across the L1, L2, N conductors, and, I submit, because of the nature of the splice or transformer failure, is shorting out the "phantom-like" voltage still being supplied by the PoCo.

This guy really explained it best
http://www.anoldman.com/power_systems/understanding_residential_ac_phases

That looks like a good reference. . . but be cautious about the use of the term "ac phase" while trying to understand the circuit theory that is dominating your problem. One of the longer threads ever in this Forum is an argument about how the term "phase" applies to a simple 240 / 120 Volt single transformer grounded-center-tap secondary. In my opinion, any of that discussion here, in this thread, will not help directly with the OPs question.

 

[KundaliniZero]

For me "on" means circuit closed and the load (house or whatever) has to have electricity.

So diference of potencial (delta V) is cero between terminals of the breaker. So your test result is ok.

When the device is off, it is closed Vl1-V'=0-0 or Vl1-V'=120-120 = 0. It depend where you put the referencw in your device.

I think you are in the same wire so probabilily your are in 120V-120V situation, if our reference is earth.

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