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Old 12-03-2008, 09:45 PM   #31
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Will reverse polarity trip breaker??


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Originally Posted by Duane 70 View Post
What should the resistance be?
With a normally wired outlet, voltage should be 0 and resistance should be very low, and most multimeters will actually be off a little at this low value, but 0-3 ohms is in the target range, depending on the length of the wire to ground and the accuracy of your meter.

However, if your outlet is truly just an open ground, voltage should be zero and resistance should be infinite (ie, no connection).


Last edited by BobearQSI; 12-03-2008 at 09:57 PM.
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Old 12-03-2008, 09:56 PM   #32
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Will reverse polarity trip breaker??


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Originally Posted by Stubbie View Post
Somewhere in your work you corrected the ground fault and now things are fine.
Thats the best I can do without seeing the situation .
I agree. From the description of your problem, it sounds like reversed polarity. However, you said that now you put everything back and just tightened some loose (but not exposed) hot wires. So my best guess is the same, that somewhere along the line you inadvertently fixed the problem.

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Originally Posted by Duane 70 View Post
I'm wondering if by removing the wire the on the outlet from the switch, making the outlet non-switched, was actually the thing that corrected the problem?
It sounds like you did some re-wiring to bypass the switch . . . maybe during part of this you corrected it? Also, if the wires were reversed upstream in the line somewhere, everything downstream could be the right color wires and screws and still be reversed polarity, so you could have missed something along the way because of that.
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Old 12-04-2008, 08:08 AM   #33
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Will reverse polarity trip breaker??


Yes, it seems somewhere I corrected the problem. The outlet still shows a floating ground. All other outlets on that circuit show good ground - both with the little circuit tester and the multimeter. Everything is wired correctly, black to gold, etc. The outlet box is plastic and the switch box is metal. I guessing it was somewhere with the switch box or switch wiring. I completely disconnected the switch out of the circuit. Now everything is direct wired to the outlet(s). One issue could have been that instead of running proper wires (insulated) from the switch to the outlet for the switched half of the outlet, they used 14/2 NM cable and just wrapped elec. tape around the ends of the ground wire in the NM cable and used that ground wire for the hot wire from the switch to the switched half of the TV outlet!!!! I have disconnected that wire from the circuit. Of course they also nice enough to cut off the ground wires in the switch box so I can't reconnect the ground to the TV outlet. Thanks everyone for your time and help with this problem. I would probably still be scratching my head if weren't for you folks knowledge and help.
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Old 12-04-2008, 08:24 AM   #34
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Will reverse polarity trip breaker??


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Originally Posted by Duane 70 View Post
Yes, it seems somewhere I corrected the problem. The outlet still shows a floating ground. All other outlets on that circuit show good ground - both with the little circuit tester and the multimeter. Everything is wired correctly, black to gold, etc. The outlet box is plastic and the switch box is metal. I guessing it was somewhere with the switch box or switch wiring. I completely disconnected the switch out of the circuit. Now everything is direct wired to the outlet(s). One issue could have been that instead of running proper wires (insulated) from the switch to the outlet for the switched half of the outlet, they used 14/2 NM cable and just wrapped elec. tape around the ends of the ground wire in the NM cable and used that ground wire for the hot wire from the switch to the switched half of the TV outlet!!!! I have disconnected that wire from the circuit. Of course they also nice enough to cut off the ground wires in the switch box so I can't reconnect the ground to the TV outlet. Thanks everyone for your time and help with this problem. I would probably still be scratching my head if weren't for you folks knowledge and help.

Thats exactly what I thought they did!

Makes more sense, the coaxial sheild is bonded with the ground in the tv, the 120 is going into the ground of the tv, finds its way through the coaxial.

Well, you need to install a ground somehow...do you have an attic above this space?

If you leave it like it is, you need to swap the 3 prong with a 2 prong outlet or install a gfci.
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Old 12-04-2008, 10:12 AM   #35
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Will reverse polarity trip breaker??


What you said about using the bare ground wire as a hot is really scary, but I can believe it!
Some people who do wiring in their homes shouldn't be touching the stuff. That's why we have professionals and inspectors!

After reading in your posts about "hot chassis", I did some testing of my equipment. I get no connection between neutral and any of the external jacks on my stereo receiver, DVD player, or TV.

As I recall, "hot chassis" TV sets came into existence when manufacturers stopped using heavy transformers. They literally used line voltage for the "low voltage" circuits, since there wasn't anything as low as we use today with microprocessor controls, etc.
The chassis was connected to the neutral prong on the plug (and a polarized plug was used)

Those TV's had to use plastic components on the outside, as well as plastic shafts on all the controls to insure the user would not be shocked if the TV were plugged in incorrectly, creating a true hot chassis condition.

These old sets never had any line input or output, just an earphone connector, which was isolated using a small transformer to protect against having line voltage on the headphone cord, so there weren't any issues with connecting grounded cables to the TV and possibly causing a short.

I do not know the construction of LCD TV, so I don't know whether they are using transformers again, or still live chassis with zener diodes and transistor regulating circuits to get the desired low voltages used in these sets.

If your new TV set has a ground prong on it's plug, I would assume that it is connected to the chassis of the set. Anything else would be foolish.

The rest of you have already covered all of the possible scenario, so I won't go back there.
I will say though, that if this were my bran-new expensive LCD set, I would not plug it into a malfunctioning receptacle.
The set has a grounded cord and plug for a reason. By plugging it into an ungrounded receptacle, you are compromising both your safety and that of the TV set.

I would be using surge protection for such an expensive TV set. I use them on all my computer and audio/video components.
Without a properly grounded receptacle, you cannot get adequate surge protection.

You really need to have an electrician in to fix this situation, or if you are competant and comfortable with electricity, do it yourself.
In the mean time, run a heavy guage (Air cond type) extension cord from a known good receptacle, and plug the TV into it.
While I do not recommend the use of an extension cord as a permanent fix, I would use it temporarily as long as it's the heavy duty type with a ground, and it is run in a completely exposed area (not under carpeting, etc) and not near any heat generating devices, or in an area that it could be tripped over, or damaged in any way.
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Old 12-04-2008, 10:45 AM   #36
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Will reverse polarity trip breaker??


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I do not know the construction of LCD TV, so I don't know whether they are using transformers again, or still live chassis with zener diodes and transistor regulating circuits to get the desired low voltages used in these sets.
Any modern digital (like LCD) TV is going to have a transformer right at the power input connected to a switching power supply that probably has a couple different voltage rails coming off of it.

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Originally Posted by KE2KB View Post
I did some testing of my equipment. I get no connection between neutral and any of the external jacks on my stereo receiver, DVD player, or TV.
Also, in newer equipment, I've always seen the shield side of the jacks connected to neutral. The reason is so that multiple pieces of equipment have the same ground reference for their signals. This is to avoid issues like ground loops (http://en.wikipedia.org/wiki/Ground_loop_(electricity)). When all pieces of equipment are plugged into the same outlet, hopefully through a surge protector, they all then have the same reference to ground.

So yes, it makes sense that older equipment would not bother to tie the connectors into neutral and go around the transformer.

On my 3-prong TV, the chasis is tied to ground and the connectors are tied to neutral.
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Old 12-04-2008, 04:07 PM   #37
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Will reverse polarity trip breaker??


I find it very surprising that UL would allow anything that is accessible on the outside of the unit be tied to neutral, since a fault somewhere in a neutral line could put the operator right in the middle of a current carrying wire!

The equipment I tested is at least 10yrs old. I'll have to see if I have anything around that's a lot newer and check it's continuity to neutral.
If it is true that the neutral is tied to the shield of the connectors, I would install GFCI receptacles or breakers on all circuits that have such equipment.
That way, at least you are protected from a lethal shock in case something is wrong with the equipment, wiring to or the receptacle it is plugged into.

Sanity check: Let me see if I am thinking correctly here: Will the GFCI trip if there is a problem?

Example 1): Bad connection in neutral at receptacle. Potential on neutral of equipment is higher than ground. Equipment is probably not working properly in this situation, due to the poor connection at neutral.
Operator comes in contact with a part of the equipment which is connected to it's neutral prong, and also to a good earth ground.
Depending on how poor the connection to neutral is, and what the person's skin resistance is, there may or may not be enough current flowing through this poor guy (or gal) to cause the GFCI to trip.
That's OK though, since the GFCI will limit the amount of current that can flow through the person to a non-lethal amount.
This is because when the person is contacting both the equipment's neutral connected chassis or connector and an earth ground, some current will bypass the poor connection (a resistance) in the neutral line at the receptacle.
This current will NOT travel through the receptacle's neutral, thus causing an imbalance between hot and neutral.

Example 2) Equipment is plugged into a GFCI receptacle, but this receptacle is reverse wired.
The receptacle will still function normally as long as the current between hot and neutral is the same.
Operator comes in contact with exposed part of equipment that is supposed to be connected to neutral, but is now connected to hot because of the reverse wiring at the receptacle, and also to an earth ground.
Current through hot wire increases due to the person acting as a small load. Current through neutral does not increase, because current through person travels to earth ground, bypassing neutral in receptacle.
GFCI trips.

OK. Sanity test passed. GFCI will save your life!
I can tell you right now that if I find that I have any equipment where the neutral is connected to any part of the equipment that is accessible to the user, I am going to install GFCI receptacle. If that receptacle trips, I am going to get rid of the equipment!

I've said my piece. Now you can debate me all you want, but it still won't change my thinking on this issue. Nothing should be tied to neutral except the power supply input!
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Old 12-04-2008, 04:18 PM   #38
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Will reverse polarity trip breaker??


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Any modern digital (like LCD) TV is going to have a transformer right at the power input connected to a switching power supply that probably has a couple different voltage rails coming off of it.
I have never seen consumer electronics use a transformer before an SMPS. It's either/or.


Neutral should not be connected to signal shields in devices, that's one good way create ground loops, not prevent them.
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Old 12-04-2008, 04:33 PM   #39
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Will reverse polarity trip breaker??


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I have never seen consumer electronics use a transformer before an SMPS. It's either/or.


Neutral should not be connected to signal shields in devices, that's one good way create ground loops, not prevent them.
Right. The transformer is part of the switcher, and isolates line from equipment.
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Old 12-04-2008, 04:37 PM   #40
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Will reverse polarity trip breaker??


To satisfy my curiosity, and preserve my sanity, I checked all of the electronic appliances that have only 2 wire cords, and found a total of zero that have any connection between neutral and any part that is externally accessible. I also checked for capacitance on some of them, and found only nanofarads there, which would not conduct enough AC to cause an issue.

Someone, please give me an example of any piece of equipment built within the last 20 years that has it's neutral tied to anything external, whether it be the chassis or a connector.
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Old 12-04-2008, 05:17 PM   #41
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Will reverse polarity trip breaker??


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Someone, please give me an example of any piece of equipment built within the last 20 years that has it's neutral tied to anything external, whether it be the chassis or a connector.

An electric dryer.
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Old 12-04-2008, 05:26 PM   #42
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An electric dryer.
Sorry (buzzz), that's not even in the same category as a TV. It's either hard wired or connected through a special plug on a dedicated line.
I'm looking for something along the lines we were discussing here.
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Old 12-04-2008, 05:28 PM   #43
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Will reverse polarity trip breaker??


It appears, at least to me that the OP's problem is that his ground was hot.
It may not be now, since he has been working on the circuit, but originally it seems likely that is what caused this whole mess.
Hot ground, connect CATV line (grounded) and sure enough, blow the breaker.

Now he said he's got an open ground, so that's much better than a hot one!
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Old 12-04-2008, 06:32 PM   #44
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I haven't the time to respond fully at the moment, but just list my equipment for now.
My definition of continuity: My multimeter reads 0.3 ohms or less. (http://www.bkprecision.com/products/...ls/?model=388B)
1) Onkyo TX-SR605 Amplifier/Receiver, released April 2007 - with everything unplugged, the neutral prong on the plug shows continuity between the entire chasis of the unit and the shield of every connector. The whole thing is almost entirely metal.
2) Toshiba HD-A20 DVD player, released some time in 2007 - neutral prong shows continuity between the entire chasis and all the shields.
3) Panamax M4300-PM surge protector - neutral prong shows continuity of the entire chasis. It also has a metal binding post on it called 'grounding post,' that is NOT continuous with neutral, but rather the ground pin of the power plug.

Also, because the receiver has neutral on all input/output shields, anything connected to the reciver is also going to get connected to neutral through the shield.

Tonight, I will re-test all of my equipment, 90% of which is pretty new, and report all models and their findings. I did all this testing about 4 months ago, and I'm pretty sure I remember the results, but I will double check tonight.

EDIT: THIS IS ALL WRONG, see my later post.

Last edited by BobearQSI; 12-05-2008 at 12:44 AM. Reason: I must have dimentia
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Old 12-04-2008, 07:57 PM   #45
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Will reverse polarity trip breaker??


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Someone, please give me an example of any piece of equipment built within the last 20 years that has it's neutral tied to anything external, whether it be the chassis or a connector.
Modern switching power supplies have input capacitors like this:

Hot----||----Ground----||----Neutral

This will always leak a few milliamps, sometimes enough to trip a GFCI.

The capacitors are class Y which means they are rated for cases where failure can lead to a direct chassis ground fault (hot-ground), risking electric shock.

Capacitors that are line-neutral are class X, rated for hot-netural.

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