Strange not-quite-240 high-voltage smoke problem... short? circuit breaker?

Hi all,
I have a puzzler and need help. I'm getting some very strange high voltages, high neutral-ground voltages, and smoke! I'm not sure if I've got a bad breaker, or a wall short, mis-wiring, or a broken ground, or ???
My sister-in-law's condo has a 2-pole 20Amp Sylvania circuit breaker circuit which provides two different phases of 120V to the following:
1st 120V pole: Garbage disposal, powered on by a wall switch. 2nd 120V pole: Dishwasher
One of the above also powers a regular wall socket but I didn't check which pole (probably the 1st). The wiring for both poles is pretty much behind the sink, likely routed next to each other from the main box.
The disposal and dishwasher have worked fine in the past, but all of a sudden, both stopped working. As the dishwasher was old and had a broken latch too, she decided to buy a new dishwasher, and nice brother- in-law that I am, I agreed to install it for her for free (tight budget).
I noticed something strange with the voltage meter from the start, which is that I still had some residual voltage on either circuit until I turned BOTH circuit breakers off. For example:
With nothing connected to either circuit (which turns out to matter but shouldn't), I measured voltages of the wires at the appliances:
1st pole (disposal) breaker OFF, 2nd pole (dishwasher) breaker ON: 1st pole: black->neutral ~12V ; black->ground ~13V ; ground->neutral ~1V 2nd pole: normal 120V (black->neutral ~121V ; black->ground 123V)
1st pole breaker ON, 2nd pole breaker OFF: 1st pole: normal 120V (black->neutral ~121V ; black->ground 123V) 2nd pole: black->neutral ~15V ; black->ground ~16V ; ground->neutral ~2V
So then, I wired up the dishwasher, turned on the 2nd pole and... nothing. The dishwasher didn't work. It didn't matter that I had just measured 120V before connecting it.
Next I plugged in the disposal, turned on the 1st pole, then the wall switch and then... the disposal ran like a bat-out-of-hell! Then SMOKE appeared at both the disposal, AND from the bottom of the dishwasher (which wasn't even running) !!!
Fortunately, when I tested both the disposal and the dishwasher on a different wall-plug circuit, both still worked fine. Nothing smoked, and the disposal motor was clearly running normal, slower than before.
One more test: With the dishwasher connected (2nd pole circuit) I measured voltages at the (1st pole) disposal wall plug (without the disposal connected, since that makes smoke), and I got the following abnormal voltages:
With both 1st pole and 2nd pole breakers ON:
2nd pole: black->neutral 206V!!! ; black->ground 123V ; neutral->ground 85V!!!
With the 1st pole breaker ON, and 2nd pole breaker OFF, it seems "normal":
2nd pole: black->neutral 121V ; black->ground 123V ; neutral->ground 3V
With the 1st pole breaker OFF, and the 2nd pole breaker ON, it's weird:
2nd pole: black->neutral 47V! ; black->ground 33V! ; neutral->ground 83V!
Oh, and by the way, during the many measurements of voltages, I got careless and managed to arc the wires at both circuits with my voltmeter probe (which lost it's nice brand new pointy tip :-O ). It neither case did either 20A breaker trip. Maybe it didn't exceed 20A, but I was a bit suprised it didn't trip the breaker).
What the heck is going on? How come the dishwasher won't work with JUST it's own breaker turned on, and with 121V no-load voltage measured?
How come I get smoke and strange high-voltages with both appliances connected and both breakers on, as soon as I turn on the disposal?
Should I just replace the breaker first, and if that doesn't fix it, call an electrician? Or is replacing the breaker a waste of time and money?
Thanks in advance for any help, Kent
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Either your a troll or not very smart, call a pro before anything else goes wrong, you probably damaged more than you realise
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m Ransley wrote:

Cammon play nice. If you expect people who ask questions to know the answer beforehand, you're in the wrong place.
--
gabriel

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Kent Monroe wrote:

Wouldn't you want to replace this with two separate one-pole breakers?
--
gabriel

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It seems as though you have a shared neutral which you failed to connect properly, thereby sending 220 volts through the appliances. This is the down-side of using a 2 pole breaker with a shared neutral to power 120 volt equipment.
Stop using your voltmeter. Your readings are normal and confusing you. Your meter is picking up voltage that is passing through each appliance. Check your neutral connection by beginning at the panel and finish where it terminates at each appliance.
If it was my house, I would run a separate line and get those 120 volt circuits off of a 2 pole breaker.
John Grabowski http://www.mrelectrician.tv

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Hi John,
Thanks for advice.
Regards to the "2 pole" breaker... I'm just reading the extraordinarily small print off the breaker. It's inside a "Sylvania breaker box 390-205-09", but I can't find any reference to Sylvania breakers. To me, the breaker looks like the pictures of the Zinsco type R38, or maybe RC38 (but there's no bar between them).
This is a thin double 20A breaker. Small type on the breaker: 2 pole, issue # LK-4137 120/240 VAC type R38 (or it could be A30, A38, R30, cause damn... it's small print) E16248 SA LR17830 It's 3/4" thick for the 2 switches, and 4-5/8" wide.
Is it possible to replace this 2-pole breaker with two single-pole 20A breakers, as another poster (gabriel, thks) suggested? Can I do this without rewiring?
My sister-in-law's place is a condo, but think "apartment" because it's surrounded above and on 2 sides by other units. She says nobody has done any electrical work in her apartment that could explain this recent failure. Routing new wires would involve tearing into walls, and major work which I'd really like to avoid, if possible (and she can't afford).
I didn't change any wires in the walls or anything, and hooking up the dishwasher is very simple. It seems unlikely that the previously working circuits were mis-wired, shooting 220 voltage though the original appliances without an immediate failure...
Therefore, something in the current wiring failed. From what you say, it sounds like the "neutral" is a common neutral for this 2-pole breaker, and I should be looking at whether that neutral is still connected between the breaker and each of the appliance neutrals.
You said:

Can you please forgive my ignorance, and suggest how? Should I turn off the house power, clip on a 20 foot wire to the breaker neutral, and do a continuity/resistor test to the neutrals of the disposal and dishwasher in the kitchen? Or is there something else you had in mind?
Is it still possible it's just the breaker which has failed, or does that sound unlikely from what I've described?
Thanks again, Kent
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Kent Monroe wrote:

Huh? Is it a breaker with two 20A switches that fit into one slot of the breaker box? The switches are _not_ tied together, and they do not trip/turn off and on at the same time, right? This has to be the case if the breaker is 3/4" thick with two switches on it...
If so, then you do _not_ have a 2-pole breaker (which is normally used for 220V circuits). You have a compound single-pole breaker.
Anyway, if this is the case, we have been addressing the problem totally wrong (so throw out _everything_ that's been said), so please confirm.
--
gabriel

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I confirm that they are _not_ tied together. However, I don't think the 3/4" size dictates which type it is. For example, see: http://www.breakerbroker.com/zintwopoltwi.html which says: Zinsco Two Pole Twin, Separately Switched, R38, vs. Zinsco Two Pole Twin, (joined), RC38
I'm guessing I have the "R38", or something similar, maybe not even Zinsco because I can't see a brand name and will bring a magnifying glass with me next visit.

So sorry if I mislead you, but the breaker says "2 pole" so I just repeated it here.
I'm going to look for a bad neutral, but as my last post says, I'd appreciate any help how to go about it. And, I'm interested to know if I can replace the breakers easily with some other (better) compatible model, and how to tell...
You guys are being a big help, thanks! Kent
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Open up the circuit breaker box. Tighten down all of the screws terminating neutral conductors on the neutral bar. After that open up every junction box, outlet, switch, and luminaire on those two circuits and confirm that the neutrals are spliced together tightly. Next go to the affected appliances and make sure that the neutral is tightly connected to the receptacles.
You can check the circuits with a pigtail socket and a light bulb or a lamp. Turn on one circuit and plug the light in. If it lights dim or not at all, you still have a problem. If it lights normal, the neutral and hot are connected. Do the same with the other breaker. Next, turn them both on and plug the light in. If it burns exceptionally bright or burns out immediately, you still have a problem.
I'm not sure who manufactures Zinsco type circuit breakers these days. I think Sylvania was at one time, but I seem to recall that Challenger was now making them. In any case you should be able to buy Zinsco circuit breakers at an electrical supply house. Changing the circuit breaker from a 2 pole to two single pole breakers will NOT get rid of the problem if it is indeed a broken neutral, but it is a good idea and worth doing unless it is a code violation in your locality.
If the circuit breaker failed, you might not have any power on those circuits. What I don't understand is why a 2 pole breaker was used for two 120 volt circuits? Is this condo located in the United States? How old is the building? Older wiring can contain many loose connections. It is possible that just by replacing an appliance, something that was loose before has now separated completely. You did mention in your original post that both appliances stopped working which prodded the purchase of a new dishwasher. Obviously there was a problem before the new dishwasher was installed.

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Kent Monroe wrote:

Just a couple of suggestions.
It sounds like that should be two independent breakers.
You should make sure you do not have a floating neutral.
Don't try to use a modern digital meter to measure the voltage. It will respond to stray current coming from lines running close to the one you are measuring. Get an old meter analog meter than has a low internal resistance to bleed off this voltage to get an meaningful measurement.
--
Joseph E. Meehan

26 + 6 = 1 It's Irish Math
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Hi Kent!
KM> I have a puzzler and need help. I'm getting some very strange high KM> voltages, high neutral-ground voltages, and smoke! I'm not sure if KM> I've got a bad breaker, or a wall short, mis-wiring, or a broken KM> ground, or ??? Part of the problem is using a digital volt-ohm meter: they tend to read voltages that aren't there. The other problem is you either have a bad contact at the circuit breakers or a loose neutral. Personally I don't like fiddling around with service panels so I'd get an electrican.
KM> My sister-in-law's condo has a 2-pole 20Amp Sylvania circuit breaker KM> circuit which provides two different phases of 120V to the following: KM> KM> 1st 120V pole: Garbage disposal, powered on by a wall switch. KM> 2nd 120V pole: Dishwasher Hmmm: one phase is the black wire and the other is red or blue? The common white could be loose in a junction or outlet box.
KM> One of the above also powers a regular wall socket but I didn't check KM> which pole (probably the 1st). The wiring for both poles is pretty much KM> behind the sink, likely routed next to each other from the main box. KM> KM> The disposal and dishwasher have worked fine in the past, but all KM> of a sudden, both stopped working. As the dishwasher was old and had a KM> broken latch too, she decided to buy a new dishwasher, and nice brother- KM> in-law that I am, I agreed to install it for her for free (tight budget). KM> KM> I noticed something strange with the voltage meter from the start, KM> which is that I still had some residual voltage on either circuit until KM> I turned BOTH circuit breakers off. For example: KM> KM> With nothing connected to either circuit (which turns out to matter but KM> shouldn't), I measured voltages of the wires at the appliances: KM> KM> 1st pole (disposal) breaker OFF, 2nd pole (dishwasher) breaker ON: KM> 1st pole: black->neutral ~12V ; black->ground ~13V ; ground->neutral ~V
These voltages probably due to stray capacitances picked up by the DVOM.
KM> 2nd pole: normal 120V (black->neutral ~121V ; black->ground 123V) I believe those reading to be withing normal limits.
KM> 1st pole breaker ON, 2nd pole breaker OFF: KM> 1st pole: normal 120V (black->neutral ~121V ; black->ground 123V) KM> 2nd pole: black->neutral ~15V ; black->ground ~16V ; ground->neutral ~2V Stray capacitances again.
KM> So then, I wired up the dishwasher, turned on the 2nd pole and... nothing. KM> The dishwasher didn't work. It didn't matter that I had just measured 120V KM> before connecting it. Try a standard light bulb? (Perhaps problem with dishwasher.)
KM> Next I plugged in the disposal, turned on the 1st pole, then the wall switc KM> and then... the disposal ran like a bat-out-of-hell! Then SMOKE appeared KM> at both the disposal, AND from the bottom of the dishwasher (which wasn't KM> even running) !!! KM> KM> Fortunately, when I tested both the disposal and the dishwasher on a differnt KM> wall-plug circuit, both still worked fine. Nothing smoked, and the disposa KM> motor was clearly running normal, slower than before. My guess is some how the wiring to one of the phases got reversed. When you connected the disposal it was receiving 240 volts instead of 120, possibly through the dishwasher (in series).
KM> One more test: With the dishwasher connected (2nd pole circuit) I measured KM> voltages at the (1st pole) disposal wall plug (without the disposal KM> connected, since that makes smoke), and I got the following abnormal KM> voltages: KM> KM> With both 1st pole and 2nd pole breakers ON: KM> KM> 2nd pole: black->neutral 206V!!! ; black->ground 123V ; neutral->ground 85V!!
Adnormal, yup! I'd be looking for a white wire is wired to 'hot' somewhere.
Continued in next message.
* Fun with Greek #4: Fee, , fo, fum!
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barry martin wrote:

No, the voltages *are* there, or the meter wouldn't register them.
What's happening is that those voltages are being fed through extremely high impedances (capacitive reactances between parallel, but not directly connected, wires.) There's enough current flow to make the meter register, but not enough to do any real work.
An easy way to keep a digital meter from being fooled by that kind of stuff is to wire a small incandescent bulb (like a 6 watt night light) across the meter leads, use two bulbs in series if you also have to measure 230 volts circuits.
Jeff
--

Jeff Wisnia (W1BSV + Brass Rat '57 EE)

"If you can smile when things are going wrong, you've thought of someone
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*Continued from previous message.
KM> With the 1st pole breaker ON, and 2nd pole breaker OFF, it seems "normal": KM> KM> 2nd pole: black->neutral 121V ; black->ground 123V ; neutral->ground 3V KM> KM> KM> With the 1st pole breaker OFF, and the 2nd pole breaker ON, it's weird: KM> KM> 2nd pole: black->neutral 47V! ; black->ground 33V! ; neutral->ground 83V! Which is why the dishwasher didn't work.
KM> Oh, and by the way, during the many measurements of voltages, I got careles KM> and managed to arc the wires at both circuits with my voltmeter probe KM> (which lost it's nice brand new pointy tip :-O ). It neither case KM> did either 20A breaker trip. Maybe it didn't exceed 20A, but I was a KM> bit suprised it didn't trip the breaker). It probably exceeded 20A but not for a long enough time to cause the breaker to trip. Similar to when you turn on an appliance with a heavy-draw start-up current you'll see the lights dim but then come back to normal.
KM> Should I just replace the breaker first, and if that doesn't fix it, KM> call an electrician? Or is replacing the breaker a waste of time KM> and money? I'm thinking the problem may be at the switch. If they used a single wire you have a white lead which is really a switched black.
- barry.martinATthesafebbs.zeppole.com
* Fun with Greek #4: Fee, , fo, fum!
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PROBLEM SOLVED!! Thanks to everyone for your replies. The advice was a big help to me.
It turned out to indeed be a floating/ungrounded neutral connection, and it also turned out to be relatively easy to spot and solve.
When I opened the (powered off) circuit breaker box and really started looking closely at all the neutrals, I could see a corroded wire whose insulation had melted and stuck to another couple of wires. One of these 3 affected wires was so loose, I doubt it was connected at all. I cut off short sections to eliminate the damage, then reconnected the neutrals to the neutral bar. I then tightened ALL of the screws in the circuit breaker box and expected all to work --- well, my original problem was solved but now a nearby light switch no longer worked, darn it.
So then (power off) I tugged on all the wire connections and found a completely loose hot wire, which had apparantly slipped out from underneath the tightening screw when I had tightened them all. Fixed it, and it's all working fine now!
I was prepared to test the ground/neutral/hot connections everywhere, and even bought a simple LED plug-in circuit tester from Home Depot that uses 3 LEDs to test for cross-wired-connections or broken wires but it turned out not to be necessary (to spot the problem). I did use it to check the connections when all was working, and it's all correct.
Thanks again to all who replied! Kent

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