Tracking down a short

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  #1  
Old 03-26-15, 05:01 PM
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Tracking down a short

I'm waiting for my local electrician to call me (probably tomorrow; I left a voicemail saying it wasn't an emergency), but thought I'd see what you guys might think of this.
We've got one 15A breaker that tripped and won't reset. After being shut off and then back on, it hums for a second or two, and trips again. One weird thing is that twice after trying to reset it (all wall switches on the circuit off and everything [AFAIK] unplugged), it seems to have made two other breakers shut off. (Not center/tripped position, "OFF off.")

The home is a circa-2000 double-wide on a full basement. The original breaker panel is by the side door. In 2009, we had a generator installed, and the transfer panel for that is in the basement. The breaker that was tripped (now left off) is on that panel. The circuit is for two bedrooms and a "hall" bath at one end of the house; the den; and one wall outlet in the living room (which backs up to the "hall" bath), and the ceiling lights in those rooms. The overhead light for the basement stairs is on that circuit, as is the ceiling light in the closet of the master bedroom. The basement stairs are closer to everything else, but the master BR and bath are at the opposite end of the house. (For reference, panels are "east end," most of the stuff on the dead circuit is "west end.") Oh, yeah; there's an outdoor outlet that's on the "hall" bathroom's outer wall. That was one of the first things I unplugged. (Had an extension cord out to my truck in case I needed to charge its battery.)

We had a rough winter, with some roof leaks, so I suspect it's something overhead. My prime suspect was the GFI/GFCI in the hall bath, which also controls the outdoor outlet, but it never tripped.

Questions/observations so far?
 
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Old 03-26-15, 05:40 PM
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Welcome to the forums! You have quite a bit on a 15 amp circuit, including a bathroom that should, by code, be on a dedicated 20 amp circuit. The humming of the breaker is telling you it is overloaded or there is a fault in the wiring causing a short to trip it. Think back to see if you added anything out of the ordinary to this circuit, like a new TV, etc.
 
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Old 03-26-15, 05:54 PM
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I agree with Larry... a very busy circuit.

The GFI would trip if there was a ground fault but would almost never cause a short.

The fact that it hums for a second or two tells me that the short is a distance from the panel. Make sure you tell your electrician about the second or two.

I have meters I use to find shorts and in your case I'd start at the master bedroom and bathroom.
 
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Old 03-26-15, 07:09 PM
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The long trip time could also signal a high resistance short.
 
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Old 03-26-15, 08:20 PM
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The long trip time can sometimes also mean an overloaded circuit.
 
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Old 03-26-15, 09:24 PM
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Thanks for welcomes and comments so far.
I gotta get used to the format here; I'm used to being able to quote replies and address specific points. Let's see how it comes out with copy-and-paste.

You have quite a bit on a 15 amp circuit, including a bathroom that should, by code, be on a dedicated 20 amp circuit. The humming of the breaker is telling you it is overloaded or there is a fault in the wiring causing a short to trip it. Think back to see if you added anything out of the ordinary to this circuit, like a new TV, etc.
Was that the code when it was built (2000)? The built-in (recessed) panel by the side door wasn't real well-labeled, but I added notes to it as we discovered things over time. For example, the two lines on the label for position #10 are written in pencil as "Lite" and "Lite." It's actually one breaker with two little toggles, each marked 15A. One is the hall, den, etc.; the other is the front and east walls of the living room.
I don't think the guys who hooked up the generator consolidated any circuits; in fact I think they might have put the refrigerator/icemaker on its own breaker. (I'll check that after The Queen of Absolutely Everything leaves for work tomorrow, so I don't get yelled at. )

There's nothing new on the tripped circuit. One or two wall outlets in the den support a printer or two, our modem and router, and there's an overhead light. The light is shut off and all the computer stuff is being fed via an extension cord from another part of the house. Nothing is plugged into the outlets in the back "hall" bedroom. It's just used for storage, and the overhead light rarely gets switched on anymore. The front hall bedroom had a portable heater that was used occasionally, but that's unplugged now. Everything's unplugged from the other two outlets in the front "hall" bedroom, and its overhead light is off when I try to reset the breaker, so I'm 99% sure the problem isn't in there.
Every dang thang I can think of is unplugged or switched off, so I'm pretty sure it's a short rather than an overload keeping it from being reset. The other big "what the heck???" is that it (#8 on the Generac panel) sometimes apparently causes #5 and #7 to shut off.

My prime suspect is the hall bathroom. It has one GFI outlet that had only an LED light with a photosensor plugged in. There are three switches next to that outlet, a pair for the ceiling fan/overhead light combo, which never gets used, and one for the lights over the sink. The "vanity" lights are on the GFI, but I don't know about the fan/light. I was using that bathroom one day and the vanity lights flickered, and I could hear some clicking each time the lights blinked. I think that's when the breaker tripped.

Some things I forgot to mention before:
1) We had mice in the overhead/walls earlier in the season, but then I stopped hearing them for awhile. I trapped 20 last fall/winter, but none this year. Now that we're having warmer days and cold nights again, they--or new ones, if the former crew got zapper--might be back.
2) There's no (human) access to the space between the ceiling and roof. Our roof pitch is pretty low, so access isn't mandated.
3) Some of the circuits that got moved to the new breaker panel in the basement are shut off at the original panel upstairs by the door. Those are the furnace (15A), well pump (ganged 20A's), and one 20A circuit labeled "Kitchen" on the upstairs box. I think that's now a 15A on the downstairs panel, which supports one wall outlet and one or two ceiling lights. The 'fridge didn't seem to be marked anywhere on the original box, but it's got its own 20A now. The outlets on the opposite side of the kitchen (north outside wall, "sink side" of the kitchen, with GFI) don't work when we're not on commercial power, nor does the range. Luckily, the microwave in on that one available south wall outlet.

On to PJMax's reply.
 
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Old 03-26-15, 10:57 PM
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I agree with Larry... a very busy circuit.
I didn't think so at first, but now that I've counted at least eight wall outlets and six ceiling lights, I'd have to agree, even if only a few of them are ever in use simultaneously.

The GFI would trip if there was a ground fault but would almost never cause a short.
I didn't figure it would cause a short, but I was a little surprised it didn't trip instead of the breaker, since my prime suspects were the outdoor outlet or maybe something on or near the ceiling in the hall bathroom getting leaked on.

The fact that it hums for a second or two tells me that the short is a distance from the panel. Make sure you tell your electrician about the second or two.
I think I mentioned that in the voicemail I left him, but thanks for the reminder. The house is maybe 60' long on its north and south sides, and the panel is on the west wall, most of that distance away from the suspect area. (I think earlier I might have mistakenly called the problem area the west end. It's actually the east end. )

I just peeked out the front door and saw the cover was up on the one socket in the outdoor outlet where the extension cord was. Snapped that shut, because there's major drippage from the raggedy gutters. I hope to get those replaced this year, along with the asphalt shingles that have seen too many Maine winters.

I have meters I use to find shorts and in your case I'd start at the master bedroom and bathroom.
I was going to ask about using a "fox/hound" combo, probably one of the audio rather than RF ones, to maybe go between outlets and see if I can narrow down the location of the short. If a DMM would work better for showing where a problem is (meaning "sudden continuity" where there shouldn't be any), I have one. I think I saw a thread (maybe more than one) on here about pulling outlets and disconnecting the hots to see if the breaker will reset somewhere during the process, but I just wondered if there was a way to track it without unscrewing too many things. A master electrician who works at the same place my wife works told her, "First, tell him to get an 'idiot stick'," and she thought that was just too funny. I know that's not going to accomplish much (nor will my DVM, except maybe on ohms) until I can at least isolate the area of the short.
BTW, I think I learned "Test the Tester" ("T.T.T.") from you guys, in another thread. See, I don't know nuthin', but I'm more or less trainable.

The only thing I know of in the master bedroom or bathroom that's on the tripped breaker is the ceiling light in the bedroom closet. (Yep, checked the bulb. Maybe the light's switch is bad, but if not, then it's the closest point to the panel for that breaker #8. BTW, the new #8 was half of breaker #10 in the original panel, the one I mentioned earlier that was only labeled "Lite" for each half of its tandem breaker. Over time, I found out the top half was pretty much the east (now dead) end of the house and about half of the north wall, and the lower half was the master bedroom and bath. (And I just found another outside light and wall outlet that are on the dead circuit, things I overlooked before. The light hadn't been used for months, and I just unplugged some things from the wall socket. )

If it's something that got wet, this rain ain't gonna help. But this is Maine, and it's Mud Season.
 
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Old 03-26-15, 11:09 PM
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You can address all questions in one post.... you don't have to separate them..... unless you want to.

Fox and Hound.... toner.... useless here. They won't work in a shorted circuit.

I have a Fluke digital meter that I use. It's one of the more expensive ones. I'll take it out of auto mode and set it to Rx1 ohms. Then I'll take the leads, short them out and use the zero mode so that the meter reads 0.0 ohms. Then I'll go to the panel, remove neutral from bar and measure from the black to the white wire and then the black to ground. That tells me what is shorted.

Then I go from device to device..... checking between black and white/ground based on which was shorted. The closest to 0.... the closest to the short.
 
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Old 03-27-15, 03:12 AM
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First, unplug that photosensor. They sometimes don't play well with GFCI receptacles. Any outside receptacle should have an "in use" bubble cover. Snap covers won't provide protection with anything plugged in, nor with the door opened. I'd open that receptacle up, make sure it is GFCI protected, dry it out and install a bubble cover.

Your generator should have nothing to do with the everyday operation of the panel. It is disconnected via a Generac switch, hopefully. Describe how it is set up for us. How did they run their wiring to the individual circuits.
 
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Old 03-27-15, 08:08 AM
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You can address all questions in one post.... you don't have to separate them..... unless you want to.
For some reason (maybe too few posts?) I can't quote others' posts the way I can in other vBulletin forums that I use. Gotta copy-and-paste, but it's a minor thing.

Fox and Hound.... toner.... useless here. They won't work in a shorted circuit.
Okay, I thought there was a way to follow the tone on a wire until it suddenly went away (i.e., via an unintended path). I guess for that one you really need to be able to see the wire, huh?

I have a Fluke digital meter that I use. It's one of the more expensive ones. I'll take it out of auto mode and set it to Rx1 ohms. Then I'll take the leads, short them out and use the zero mode so that the meter reads 0.0 ohms. Then I'll go to the panel, remove neutral from bar and measure from the black to the white wire and then the black to ground. That tells me what is shorted.
As in hot-to-ground s/c vs. hot-to-neutral, right?

Then I go from device to device..... checking between black and white/ground based on which was shorted. The closest to 0.... the closest to the short.
Okay, that's probably something I could do. The "divide-and-conquer" thing.
Thanks.
 
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Old 03-27-15, 08:41 AM
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For some reason (maybe too few posts?) I can't quote others' posts the way I can in other vBulletin forums that I use.
Blame the lazy idiots who quote the whole post instead of just the relevant parts like you did.
 
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Old 03-27-15, 10:47 AM
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First, unplug that photosensor. They sometimes don't play well with GFCI receptacles.
It's just an LED nightlight, maybe zero-point-something amps, but I'll keep that in mind. The GFI in that bathroom hasn't tripped for anything in awhile.
A local carpenter built some new steps for us back in September, and his circular saw had a crappy cable. It tripped something, but I can't recall if it was the breaker or the GFI.
Is there any way to test a GFI that doesn't have power to its circuit?

Any outside receptacle should have an "in use" bubble cover. Snap covers won't provide protection with anything plugged in, nor with the door opened. I'd open that receptacle up, make sure it is GFCI protected, dry it out and install a bubble cover.
I know it's "downstream" from the GFI in the hall bathroom, because that's where I had to go to reset the dang thang anytime a tool or something popped the GFI. I thought it had its own Test/Reset, but no. (Provides a good excuse for a break from yard work, but if something kicks the protection too often, I know that's not good.)

Good tip on the bubble cover; thanks. (I just found the DIY.com thread on bubble/in-use covers. I try to learn something new every day, preferably without breaking anything during the learning process. )
I'll have to wait for the weather to improve before I can do anything much with that outlet. By that time, the electrician will probably have been here. (We're scheduled for around 7:45 Monday morning.) At least we've had some off-and-on sunshine today.

Your generator should have nothing to do with the everyday operation of the panel. It is disconnected via a Generac switch, hopefully. Describe how it is set up for us. How did they run their wiring to the individual circuits.
As I mentioned earlier, it's on a transfer switch. It might be a discontinued model, Generac's eight-circuit/100A one.
Maybe this photo will help. Apologies if I'm not up to speed on terminology. (Hey, I know the difference between "cables" and "wires"--usually.)
Name:  GenWiring_1.jpg
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I believe the armored cable is the feed from the generator to the Generac panel (the breakers portion of which is below the bottom of the image frame), the large gray cable running horizontally at the top of the basement wall is commercial power in/up to the original (Square D) panel, and I think the large black one above the unmarked square box is the (commercial) feed from the original panel to the new panel.
The white and yellow "flat" conductors on the unmarked square box go to or from the original panel. The ones in the smaller conduit go to/from the sewer pump and its alarm.

Back to the breakers in the original panel that are now served by breakers in the Generac box: All were switched off except the tandem 15A's for the "hall" bedrooms/bath (plus den), and the master bedroom/bath/living room. The lower half of that tandem is now breaker #7 on the Generac, and the upper part is breaker #8 on the Generac. (The tripped breaker.) Everything on #7 still works after I shut the original (tandem) ones off, but the tripped breaker still would'nt reset.
 
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Old 03-27-15, 10:50 AM
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Originally Posted by ray2047
Blame the lazy idiots who quote the whole post instead of just the relevant parts like you did.
Ah ha; I hear ya on that. I do try to not leave messes behind me. (Although my wife would disagree with that claim. )
 
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Old 03-27-15, 02:57 PM
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Update: Pulled out the low-budget DMM, and began testing outlets. I guessed that the Rx1 that PJmax mentioned was the lowest setting, which is 200Ω on mine.
I started with the hall/"spare"bathroom outlet, and saw maybe 2-3Ω hot-to-hot, neutral-to-neutral, and ground-to-ground between the two receptacles. It didn't seem to do anything hot-to-neutral, hot-to-ground, or neutral-to-ground. (Meaning "infinity.") Then I moved to the front hall bedroom, which shares an interior wall with the bathroom, and things changed. I seemed to get pretty much the same low readings in the wrong places as I did where I'd expect to see continuity. The hall outlet (on the marriage wall, about across from where the bathroom outlet and switches are) did the same.

I went out and checked the outdoor outlet (which is GFI, "downstream" from the hall bathroom outlet), and it was the same as the bathroom outlet. The one living room outlet that's not on the same circuit as the master bedroom (the interior wall it's on backs up to the hall bathroom wall that has the vanity lights on it) seemed the same as the front bedroom and hall outlets.
Checked one of the outlets on the north wall of the den and the one I had forgotten until last night. (The one that's under the switch for the back deck light.) The one in the den was the same as all the non-GFI ones. Just in case I misunderstood what PJmax wrote, I cranked the meter selector knob up to 2000KΩ. That might have been a dumb idea. I started getting negative numbers in all the places where there was continuity, but otherwise it seemed to act like most of the others. Now when I touch the probes together with it on 200Ω, it shows upwards of 70Ω instead of the 2.0 or less I was getting before. I'm hoping that's just the batteries.

Am I doing it right so far?
 
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Old 03-28-15, 01:17 PM
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Today I started trying to narrow down the location of the short. Thinking the outdoor outlet was a good place to start, I opened up the hall bathroom GFI outlet and pulled the load wire off it, and tried to reset the breaker. That didn't accomplish anything, so I pulled both line wires off it. Still no reset.

I assume (yeah, I know that old saying) that rules out the bathroom outlet, the outdoors outlet, and the four light sockets over the vanity.

Next stop: the bathroom ceiling fan/light.
 
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Old 03-28-15, 09:20 PM
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Let's just take a quick step back. Yes.... the 200ohm is your lowest setting.

It is critical that you never connect a meter set to ohms to 120vac. Be sure you don't try to check any live receptacles or the meter could literally explode.


A short is 0 ohms. You need to get your meter to read 0 every time you touch the leads together. If you can't do that.... your testing will be useless. The idea is the closer you are to the short... the lower the reading.

You go to the panel and pull the white wire out of the bar. Check from black to white and from black to ground. One of them will show the short. Try to get an accurate resistance reading. I'm going to guess and say 2 ohms.

Now go the farthest location from the panel. Measure it again. I'm going to guess .5 to 1 ohm.

Now go the middle and measure. Compare your readings. The lowest reading is the area where the short is.

This is why I use a really good meter and auto zeroing. The resistance numbers you are working with are very low and will be very close. I look for very fine differences between the readings. I can usually find the short in under 1/2 hour.
 
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Old 03-29-15, 01:10 AM
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Let's just take a quick step back. Yes.... the 200ohm is your lowest setting.
Okay. I just wasn't 100% sure if that was the same as "Rx1."

It is critical that you never connect a meter set to ohms to 120vac. Be sure you don't try to check any live receptacles or the meter could literally explode.
That, I knew, but I appreciate the reminder. The breaker won't reset, so I know it's off (and I leave it "OFF off" between tests), but I always stop before I insert the probes into any outlet and ask myself "How do you KNOW this circuit is off?"
BTW, UPS says my new Fluke 2AC VoltAlert tester will be here Friday. I hope it arrives sooner. That can be one final check before I test anything, or maybe I'll start out with the multimeter's selector on AC Volts before doing resistance testing.
"Safety awareness helps avoid rude surprises."

A short is 0 ohms. You need to get your meter to read 0 every time you touch the leads together. If you can't do that.... your testing will be useless.
I wish my meter could be zeroed. I think it's time for this "generic" one to be replaced, anyway.

The idea is the closer you are to the short... the lower the reading.
Okay, that's what I thought. I just wasn't sure if the 2.4 to 3.5 ohms readings I was seeing when measuring hot-to-neutral and hot-to-ground in those various outlets were valid. I was also seeing about 2.5 ohms when I checked anything hot-to-hot, neutral-to-neutral, or ground-to-ground.
The bathroom and outdoor outlets (GFI) weren't showing anything between differing sides (hot-to-neutral or ground), only where I'd expect to see continuity (hot-to-hot, etc.).

You go to the panel and pull the white wire out of the bar. Check from black to white and from black to ground. One of them will show the short. Try to get an accurate resistance reading. I'm going to guess and say 2 ohms.

Now go the farthest location from the panel. Measure it again. I'm going to guess .5 to 1 ohm.

Now go the middle and measure. Compare your readings. The lowest reading is the area where the short is.

This is why I use a really good meter and auto zeroing. The resistance numbers you are working with are very low and will be very close. I look for very fine differences between the readings.
Alright, I'll try that. I was hoping to sniff out the short without sticking my nose into the panel, but I'll start there and work outward, instead of working from the "outlands" back toward the breaker box.
Is it a pretty good bet that anything on a switch, with the switch off, is much less likely to be the problem? (Guessing that the problem is more likely to be in a wall socket or other place that's always "live," even without anything plugged into it.)

I can usually find the short in under 1/2 hour.
That's where you've got me beat; Education and Experience wins out.
 
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Old 03-29-15, 01:48 PM
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If you think logically you'll find the problem.

The reason for removing the neutral is that currently the neutral and ground are connected in the panel hampering your testing.

That Fluke tester is just a voltage probe. It's ONLY job is tell you that there is dangerous high voltage in the area. In this case since you have a dead short.... it will show you nothing rendering it un-useable for this repair.

Your meter doesn't have to always come to 0 but it must always come to the same point. If you can only set the meter as low as two ohms.... that's fine. Take all your measurements from there.

The problem is in the area where the resistances measured are the closest to your shorted probe reading.
 
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Old 03-29-15, 09:35 PM
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If you think logically you'll find the problem.

The reason for removing the neutral is that currently the neutral and ground are connected in the panel hampering your testing.
Got it now. That part had eluded me.

That Fluke tester is just a voltage probe. It's ONLY job is tell you that there is dangerous high voltage in the area. In this case since you have a dead short.... it will show you nothing rendering it un-useable for this repair.
Could I get some credit for a little knowledge, even if I have darn little? I know it's hard to tell for awhile whether the new guy might be "a danger to himself and others," but I'm not completely inept.
That device was purchased solely for use as a last safety check to make sure I don't blow up a multimeter (or worse), something mentioned in a prior post. Since the breaker is shut off, I'm not expecting any indication from the VoltAlert, but as I've learned through the posts here (and in some other threads), that's the reason for using one: preventing some possible "what the hell???" moments.
I'm certain there are no circuits in the house that might be fed from more than one source (something I saw in fallen overhead lines once while I was on a traffic detail at a car-vs.-pole crash scene years ago ), but I'd rather just avoid any unpleasant surprises. Kind of a "Measure twice, cut once" thing, but with more at stake. Or as Kopcha's Rule says, "There is always one more son of a ***** than you counted on."

Your meter doesn't have to always come to 0 but it must always come to the same point. If you can only set the meter as low as two ohms.... that's fine. Take all your measurements from there.
Got it; I was at least getting the similar readings in similar situations (point-to-point on the same conductor, etc.). It showed very low resistance in the places I expected to see that, and I figured anything above zero was just from the wire and connections, and any inherent in the meter itself. But the low resistance at places where I expected it to be infinite was what flummoxed me. That was probably due to my improper technique.

The problem is in the area where the resistances measured are the closest to your shorted probe reading.
Alright; on Monday, I'll buy a new meter, disconnect that neutral at the bus bar, and start anew.

Also, does anyone have any input on the likelihood of a light fixture being the problem spot? (Switched off now, and rarely used before the problem.) I want to test first on places that are easiest to access, so ceiling outlets would be last on my list. I already discovered that while the GFI outlet in the hall bathroom had backstab connections, the wall switch for the ceiling light in the master bedroom closet (still wondering why that's on that circuit) has some I didn't expect. The wires are looped around the screws, which is okay, but the screws don't seem to back all the way out so the looped wires can be removed. I'm assuming the loops were formed and then screwed down, but I didn't want to reef on the screws and break something. It's a colossal pain to work on in a confined space like the closet. (And I'm sure you pros have encountered way worse locations than that.)

The tripped breaker apparently causing two nearby breakers to shut off is another thing that no one's commented on yet. It's only happened twice so far, but I probably haven't attempted to reset the tripped breaker more than 10-12 times since it first kicked out.

Thanks.
 
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Old 03-29-15, 10:07 PM
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Get an analog not digital multimeter. For this it will be visually easier to read. For voltage readings it is less likely to give you a false reading. An $8-$15 one is all you need.
 
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Old 03-29-15, 10:19 PM
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If it's a light that is controlled by a switch.... then as long as the switch is off it should the light as a problem.

I didn't mean to belittle you about the voltage probe. Those things are great and do have their place. As far as checking if a receptacle is live before using the ohmmeter is a great idea.

Keep this in mind for the future. You have a circuit in the house go dead. Half the receptacles are working. You come in with your tester and all receptacles show live. What now you think. The probe tester has confirmed power but since you lost a neutral the circuit is no longer complete. The probe cannot check for neutral.


Just to repeat myself again..... you are working with very close resistances. Maybe only an ohm or two throughout the entire circuit so slight differences are very important.

A backstab issue will not be your problem. A backstab issue will cause an open circuit. Based on removing the neutral from the panel you will find out if you have a short to neutral or short to ground.
 
  #22  
Old 03-30-15, 09:48 AM
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Originally Posted by ray2047
Get an analog not digital multimeter. For this it will be visually easier to read. For voltage readings it is less likely to give you a false reading. An $8-$15 one is all you need.
Ah ha; I thought I had seen a mention of an analog meter somewhere along the way. Thanks for the tip, Ray.

Originally Posted by PJmax
If it's a light that is controlled by a switch.... then as long as the switch is off it should [rule out] the light as a problem.
Okay; and it's more likely to be something that's "always live," like a wall outlet, right?

I didn't mean to belittle you about the voltage probe.
Nah, it wasn't belittling; I might have been unclear earlier about how I intended to use it.
It did take me a little while to "suss out" the suggestion from the electrician my wife works with about "first, tell him to buy an 'idiot stick'." At first I thought, "Well, that ain't gonna work on a dead circuit." Then I realized "Oh, okay; that's how we can initially and periodically confirm that it's a dead circuit."

Those things are great and do have their place. As far as checking if a receptacle is live before using the ohmmeter is a great idea.
Cool; thanks.

Keep this in mind for the future. You have a circuit in the house go dead. Half the receptacles are working. You come in with your tester and all receptacles show live. What now you think. The probe tester has confirmed power but since you lost a neutral the circuit is no longer complete. The probe cannot check for neutral.
And now I'm finding out the subsequent steps to determine if it's a lost neutral, etc. "With a little help from my friends."

Just to repeat myself again..... you are working with very close resistances. Maybe only an ohm or two throughout the entire circuit so slight differences are very important.
I made a crude sketch of the outlet locations as I checked them the other day, and wrote down the ohm readings for each. Maybe the next time I make those tests, with the neutral off the bar, the readings will be a little more significant.

A backstab issue will not be your problem. A backstab issue will cause an open circuit. Based on removing the neutral from the panel you will find out if you have a short to neutral or short to ground.
I mentioned that outlet just as a comparison to the light switch which had different terminals. The one with backstabs was a heck of a lot easier to disconnect/reconnect than the one where the screws didn't seem to want to release the wires so I could do more testing. There are some kind of clamps over the loops, so they can't just be lifted off when the screws are backed out. "It's a gigantic pain in the ***," as Griffin said in MIB 3.
If the switch (or its related outlet) is less likely to be the problem point, that;s a Good Thing.
 
  #23  
Old 03-30-15, 02:50 PM
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Bought a little Gardner Bender analog VOM (GMT-312) and a Greenlee DM-25 this afternoon. Then I went and peeked inside the Generac panel. (It's not too scary, if I keep both hands in my pockets and don't put my nose or anything too close to it.)
I haven't pulled the main breaker yet, trying to choose a time when the furnace isn't running, so I won't have to open it up and reset it. So all hots are being regarded as HOT until proven to be NOT.

While I was in there, I tried resetting the tripped breaker a couple of times, and saw a small flash and heard a little "snap!" that I hadn't noticed before. I caught that on video, if anyone thinks it might shed some light (pardon the pun) on this. I won't attach 'em (MP4's) unless you want to see.

Here's a pic of the inside of the panel. If I called the tripped breaker #8 in prior posts, it's actually #7.
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I'm guessing the slightly larger white wire at the top of the bar is for the ganged 20A breakers at the top left, and the other six wires are for the single breakers.

Meanwhile, I'll go get some measurements with one or both of my new meters.
 
  #24  
Old 03-30-15, 09:46 PM
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I wouldn't keep trying to reset the breaker. It only has so many dead short resets in it. Every time you reset it your arcing the contacts. Yes..... it's normal to see an arc.

Most panels are labeled as below....

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  #25  
Old 03-30-15, 11:38 PM
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Yeah, I finally remembered the odd-numbers-left thing.
I tried to edit my previous post, but had run past the 180 minutes. So the tripped breaker is #6.

Retracing some steps:
Originally Posted by PJmax
You go to the panel and pull the white wire out of the bar.
To confirm, do you mean the white for breaker #6?
I forgot to mention earlier (and found it was too late to edit), but I had removed the bottom three neutrals one at a time and tried resetting the breaker, and that was when it arced. Assuming breakers 1 and 3 have a common neutral, I tried to figure out which one of the other six would be for breaker #6. Since it seemed to be arcing to the neutral bar, I tried an experiment. With the breaker still off (it's not going to do much of anything but trip or remain off, apparently) I measured VAC from its hot to the neutral bar, and got zero. I checked resistance, and the meter beeped, showing about 1.2 to 1.5 ohms.

I checked breaker #5 the same way, first volts with it On (~120), and zero volts when Off. Then I checked resistance hot-to-neutral, and that was infinite.

I've now gone around and gotten some hot-to-neutral and hot-to-ground readings on various outlets and switches. I think the GFI outlets in the hall bathroom were showing around 7.5 ohms. Various ones in the front hall bedroom and den were down around 1.5-2, and I saw 0.7 on the switch for the back deck light. The reading flickered around a lot, but that was the lowest I saw. I'd expect higher resistance when the connection wasn't good (it's not easy holding all that stuff steady), but I thought <1 was kinda weird.
None of the wall switches so far has had a neutral on it, just two hots (line/load) and a ground. There's a bundle of white wires in the back of the switch box, maybe with a wire nut, but those wires seem to just go up the TPS in the wall toward the ceiling, along with the hots from the load side of each switch.

Time to rake a break from it until later today. (It's Tuesday already.) I'll make a better diagram and write down the readings then.
 
  #26  
Old 04-05-15, 02:27 PM
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The only new development here is that the (hall) bathroom GFI outlet and the outdoor outlet "downstream" from it are now showing infinity when measured hot-to-neutral, where they had been around 7.5 ohms before. Other outlets on the circuit are still reading around 1.5 ohms.

I'm going to replace the outdoor outlet with a WR/TR one, "just because," and add a While-in-Use cover over it.

Any suggestions for finding which neutral on the bar goes with breaker #6, short of disconnecting and capping all of them, one at a time? (And what are the chances that the breaker isn't arcing to just its own neutral on the bar, but to the bar itself?)

Originally Posted by PJmax
I wouldn't keep trying to reset the breaker. It only has so many dead short resets in it. Every time you reset it your arcing the contacts.
Yeah, I might replace it on general principles, but would prefer to avoid that. But until I locate that circuit's exact neutral wire and cap the wire (if that's where the arc in the panel is going), won't I be just "spinning my wheels" trying to find the location of the short?

Thanks.
 
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