Continuity between phase conductors, neutral, and ground

[Jacobbaker522]

Hey everyone,

I had a client contact me after she woke up in the middle of the night to a loud pop. When she got up the next morning all of her individual breakers in a main lug panel had tripped. She reset all of the breakers and everything held. She then called me to come take a look. When I arrived I tightened all of the connection on each breaker as well as the incoming feeders into her panel. This unit is a condo building and her service is 120/208. I grabbed my multimeter to check voltage and continuity. All voltage read correct, but I checked continuity I was getting a very loud ring between both phase conductors, neutral, and both phase conductors to ground. I was also reading over 500 ohms when checking between phases. The panel was energized while I was doing this test so I am assuming that is why I had such high resistance between everything. My question is why would I have continuity with a high pitch ring on my fluke meter between my phase conductor and grounding conductor. Wouldn't this indicate a short?

Thanks for your help.

 

[jim dungar]

Why are you checking continuity on live circuits?
Meters have been known to explode when this is done.

 

[Jacobbaker522]

Why are you checking continuity on live circuits?
Meters have been known to explode when this is done.

I did not have the ability to turn off the main breaker and I wanted to make sure the I did not have any shorts between conductors. Do you think because I performed this test while it was live I may have fried my tester and that is why I am getting the ringing between my hot and ground?

 

[jaggedben]

Your meter's loud ring is its way of warning you that you are measuring a live circuit on the wrong setting and should stop. It does not indicate a short. And you should ignore any ohm readings in that situation.

 

[Jacobbaker522]

Your meter's loud ring is its way of warning you that you are measuring a live circuit on the wrong setting and should stop.

Okay, thank you for that information.

 

[jaggedben]

Are the individual breakers all AFCIs? I can't think of much that would plausibly trip all the branch breakers in a panel if they weren't AFCIs. Never seen that sort of thing happen,.

 

[Jacobbaker522]

Are the individual breakers all AFCIs? I can't think of much that would plausibly trip all the branch breakers in a panel if they weren't AFCIs. Never seen that sort of thing happen,.

I haven't hear of it happening before either, there are no AFCI's. My first thought was there was a surge from the utility, but as far as I am aware it only occurred in this one unit. Everything is operating correctly and no equipment was damaged, but I was wondering if anyone had any thoughts on the issue for why each of the branch circuit breakers tripped.

 

[LarryFine]

Welcome to the forum.

The panel was energized while I was doing this test . . .

You need to hire an electrician.

 

[Jacobbaker522]

Welcome to the forum.


You need to hire an electrician.

Do you have any idea for why each of the individual branch circuit breakers would have tripped?

 

[Little Bill]

Do you have any idea for why each of the individual branch circuit breakers would have tripped?

Did you witness them tripped? If not, the customer might have been mistaken. They could have turned them all off, then back on thinking that would help. I've had customers tell me half there power was out when it was only one circuit.

 

[ptonsparky]

Be glad you had a half way decent meter. They used to do a rapid disassembly in front of your face.

 

[PizzaSolei]

Calling Fluke about your experience with your meters response would be educational.

 

[Jraef]

Aside from the dangerous nature of what you did, you will read continuity through any and every load that is connected without an actual switch. So every wall wart power supply/charger, most large appliances now that have a display and/or clock, anything on a solid state switch like a dimmer or “smart” switch, etc.

But don’t do that again!

 

[MD Automation]

I am pasting some content I posted earlier this month regarding a similar thread about trying to measure resistance on a live circuit. I am including it here just in case it helps the OP understand something about how an ohm-meter functions - and why having other voltage sources also present in the circuit can make the ohm-meter's reading inaccurate.

<snip>

Fyi... using an ohmmeter to read resistance while the conductors are energized will not give you valid readings.

Your meter has a battery and to get a measure of resistance in a circuit, that little battery causes some current to flow across whatever you are trying to measure. Then the meter reads the voltage drop it sees and turns that into a resistance measurement. This is a long way of saying that a standard ohmmeter is really measuring voltage - and using Ohm's Law to turn the measured voltage into a reading of ohms. And the source of that measured voltage MUST be from the meter's battery and ONLY the meter's battery.

So you don't want to use an ohmmeter with the power turned on. That introduces another source of voltage (however small) that will "confuse" (mathematically) the meter's reading.

<snip>