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Old 12-04-2008, 08:59 PM   #46
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Will reverse polarity trip breaker??


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Originally Posted by BobearQSI View Post
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.
Are you... completely unplugging the equipment first?

You do realize that if it's plugged in (or anything connected to it is plugged in), you will get continuity from the ground bonding at your service panel, right?

The only proper way to test this is to completely disconnect all the power and signal cables.

I think this is where your confusion comes from. Even if you unplug say your DVD, if it's got coax to a plugged in TV, you will see ground-neutral continuity.

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Old 12-04-2008, 09:31 PM   #47
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Will reverse polarity trip breaker??


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Originally Posted by Gigs View Post
Are you... completely unplugging the equipment first?

You do realize that if it's plugged in (or anything connected to it is plugged in), you will get continuity from the ground bonding at your service panel, right?

The only proper way to test this is to completely disconnect all the power and signal cables.

I think this is where your confusion comes from. Even if you unplug say your DVD, if it's got coax to a plugged in TV, you will see ground-neutral continuity.
I got the impression that he was checking with the device unplugged, measuring from the neutral blade of the plug to chassis.

I guess things have changed since the last time I purchased electronic equipment, as none of my equipment is less than 10 years old.
There is one exception though; A Canon multi-function printer. It doesn't even have a polarized plug, and of course there is no continuity between either blade and anything metal on the device.

With this configuration being approved for electronic equipment, I would think that a GFCI receptacle should be mandated for every receptacle in the house, since such equipment could at any time cause a lethal shock if the conditions are right (as I discussed in my previous post).

Oh yea; One thing I forgot to ask; Are you living in the US? If not, then all bets are off! I know that other countries have different wiring configurations. If the power delivery system does not use a ground reference, you have no connection between either line conductor and ground, so there isn't such a risk if something gets "hot".
All of us (who understand power delivery systems even to a small degree) know that without that connection to ground on one side or the CT of the transformer, you have no issues when someone comes between either conductor and earth. Wouldn't it have been nice if our POCO's had done this from the very beginning! Of course we all know why they did use the ground as a conductor $$
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Old 12-04-2008, 09:54 PM   #48
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Will reverse polarity trip breaker??


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Oh yea; One thing I forgot to ask; Are you living in the US? If not, then all bets are off! I know that other countries have different wiring configurations.
No country would ever allow any device to directly tie current carrying neutral to the chassis ground. He's testing it incorrectly or misinterpreting the results or something.

The IEC grounding classes are international, and none of them would allow this.
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Old 12-04-2008, 10:24 PM   #49
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Will reverse polarity trip breaker??


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Originally Posted by Gigs View Post
No country would ever allow any device to directly tie current carrying neutral to the chassis ground. He's testing it incorrectly or misinterpreting the results or something.

The IEC grounding classes are international, and none of them would allow this.
I agree with you, yet I am intrigued by all of this.
Perhaps they are taking ohmmeter readings while the device is connected to grounded CATV or other external wiring, and measuring between chassis and the neutral slot of the receptacle.
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Old 12-04-2008, 10:39 PM   #50
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Will reverse polarity trip breaker??


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Originally Posted by KE2KB View Post
I agree with you, yet I am intrigued by all of this.
Perhaps they are taking ohmmeter readings while the device is connected to grounded CATV or other external wiring, and measuring between chassis and the neutral slot of the receptacle.
That's what I was thinking, somehow they were seeing the neutral bonding at the panel.
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Old 12-05-2008, 01:36 AM   #51
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Okay, so I don't know what I must have been smoking 4 months ago. Neutral is NOT tied to any of my chasis or connectors. I was trying to find the source of a ground loop problem that could only be heard when HDMI devices were plugged into my receiver/amp. I thoroughly analyzed everything. I eventually determined it was a problem with the amp, and sent it in for service and got it back fixed. All I can think of is that neutral being connected to the chasis was the problem with the amp, and they fixed it. I explicitly remember holding one end of the multimeter to the large end of a 2 ponged only plug on my amp, and the other to all the connectors. I'm pretty sure I wasn't seeing ground/neutral binding at the panel, because I was testing both hot and neutral with all sorts of parts on the equipment, and that wouldn't have gone well where other things connected through to a live outlet. Plus, the resistance from neutral to ground at the socket is about 2 ohms rather than 0.2, I'd hope I'd have noticed that.

Anyway, I re-tested everything tonight, and nothing was connected to neutral at all. All devices with 3 prong sockets had their chasis and all connectors hooked to the ground pin. All 2 prong sockets had floating ground/chasis. Sorry for the mis-information here. You all must have felt like this guy: http://xkcd.com/386/
Yes, I do live in the US, too.

Secondly,
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I have never seen consumer electronics use a transformer before an SMPS. It's either/or.
I don't know of any electronics SMPS that doesn't have a transformer. They usually convert AC current to DC and/or AC current of a lower value. Maybe the confusion what how I said it, what I meant was 'a transformer is usually part of a SMPS.' An example is the first picture here: http://en.wikipedia.org/wiki/Switched-mode_power_supply where the transformer is clearly labeled.

So, back to the original issue with Duane's TV and wall socket, I think I now may know what the problem could have been: The bare hot wire was probably touching some part of a screw or other ground on the actual outlet itself. He said the box was plastic, but sometimes the metal screw connecting the outlet is long and is exposed inside the box. That would make the ground pin hot through the screws in the receptacle. And obviously no ground wire because the ground and hot could touch.

The ground was hot, thus the TV chasis was hot when connected, and then connected to CATV's seperate ground when plugged in. The problem is gone now because after re-wiring, the hot wire is no longer touching the screw or outlet other than where it should be.

Duane, I think everyone agrees here that this bare hot wire and no ground needs to be fixed permanently. If it even barely touches the screw, the same thing will happen again. You said there was tape around the wire, was that both ends (at the switch and the outlet)? Either way, its not good on many levels to have a bare hot wire running behind the wall, probably touching insulation, possibly nails, or who knows what.
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Old 12-05-2008, 01:42 AM   #52
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Will reverse polarity trip breaker??


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I agree with you, yet I am intrigued by all of this.
Perhaps they are taking ohmmeter readings while the device is connected to grounded CATV or other external wiring, and measuring between chassis and the neutral slot of the receptacle.
Also, no CATV here. Just satellite and a small, self-built antenna, neither of which is grounded to earth. Unless my roof has grounded metal hiding in it. They are grounded through the surge protector, though, but like I said, my testing of hot to chasis wouldn't have gone well if stuff was plugged in.
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Old 12-05-2008, 08:07 AM   #53
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Will reverse polarity trip breaker??


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Originally Posted by BobearQSI View Post
Also, no CATV here. Just satellite and a small, self-built antenna, neither of which is grounded to earth. Unless my roof has grounded metal hiding in it. They are grounded through the surge protector, though, but like I said, my testing of hot to chasis wouldn't have gone well if stuff was plugged in.
I thought sat systems were always grounded to earth before the line enters the house. Are you sure yours doesn't have a ground wire running down from the dish?
IMO, it should be grounded to protect you and your equipment against lightning surges (not even a direct hit).
During storms, you can get some pretty heavy currents flowing through ground wires. In your case, the current would have to flow through the shield of the coax into your home before finding a ground. That could conceivably cause a fire.
Same reason all of my amateur antenna were (no longer have them up) grounded by rods as close to the antenna as possible.
It is also important from an RF point of view. More important for transmitting antenna than receiving though.

I recall once reading a story by Ansel Adams. He was standing on a beach in CA, photographing a storm coming over the cliffs, or maybe it was coming in over the ocean, not sure.
He thought it was time to get out when his tripod started to get warm!
The tripod was conducting a heavy current from the atmosphere due to the approaching storm.
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Old 12-05-2008, 08:44 AM   #54
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Will reverse polarity trip breaker??


Thanks guys. Just to clarify about the hot ground wire. What the original wirer did was use the ground wire encased in the 14/2 NM cable sheath as the hot connection from the switch to the outlet (only half of the outlet was switched). Where the ground wire exited the NM cable, they wrapped black elec. tape around it for insulation. I as far as I know, the configuration was like for the 30 years the house has been built with no problems manifesting themselves until I plugged the 3 prong cord on the new TV. I recall if anything else with a 3 prong cord was ever plugged into the outlet or not. When I decided a couple of nights ago to pull the switch to see what was inside the box, I could hear some sparking going on. When I pulled the wires from the box, there was a short section of exposed bare "ground" wire that the tape was not covering. I don't know if that exposed section of wire was contacting anything else in the box or not. Also, when I wiggled the wire nut on the black wires, I could hear sparking. I turned of the breaker and removed the wire and found the connections were loose. The switch was wired to the outlet as follows: a short jumper wire (again a piece of bare ground wire wrapped with elec. tape for insulation) from the hot wire nut connection to one terminal of the switch; from the other terminal of the switch - the ground wire in the NM 14/2 cable from the switch box to the outlet box was taped with black tape from the cable sheath to the switch for insulation (this tape was also fairly loosely wrapped). From the switch, the ground (now "hot") wire travels in the NM cable sheath to the gold screw on the top half of the TV outlet. The outlet end of the ground (now hot) wire is also wrapped with black elec. tape. So it seems somewhere, somehow, the wire from the switch to the outlet must have been making contact somewhere it shouldn't have been. I removed the short jumper wire in the switch box completely and re-twisted and re-nutted the black wires in the switch box (also re-twisted and re-nutted the white wires). I also removed the taped up "ground" wire from the outlet and re-taped it up. That wire is now not connected at anything at either end (switch box and outlet box) so I no longer have a switched outlet (just a switch in a box that is not conneted to wires). I also replaced the outlet itself with a new one because the old had the tabs between the screws removed so that only one half (the top half in this case) would be switched. Does this help clear up anything I confused folks on earlier or make things any more sensible?? Thanks again for all of your help and suggestions.
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Old 12-05-2008, 02:57 PM   #55
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Will reverse polarity trip breaker??


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What the original wirer did was use the ground wire encased in the 14/2 NM cable sheath as the hot.

I'm glad you called him a wirer and not an electrician. Whoever that guy is, he should be sued into oblivion.

Call an actual electrician to check every box and circuit in your house. I could not sleep at night knowing that kind of wiring was in my house. It might cost a couple hundred bucks to have him check over everything, but it'll be well worth it.
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Old 12-05-2008, 03:04 PM   #56
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Originally Posted by BobearQSI View Post
Anyway, I re-tested everything tonight, and nothing was connected to neutral at all.
Yeah it could have been one faulty device confusing you.

Quote:
I don't know of any electronics SMPS that doesn't have a transformer.
That's right, they all have a transformer. It's a high frequency transformer that operates around 30 to 60 kilohertz though, it's not doing anything to the line power.

Quote:
They usually convert AC current to DC and/or AC current of a lower value.
Transformers are always AC to AC devices. Saying AC current is like saying ATM machine. Sorry I'm being pedantic. :P

Quote:
Duane, I think everyone agrees here that this bare hot wire and no ground needs to be fixed permanently.
I agree there.
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Old 12-05-2008, 03:25 PM   #57
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Will reverse polarity trip breaker??


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It's a high frequency transformer that operates around 30 to 60 kilohertz though, it's not doing anything to the line power.
Right, the point I was making when I originally brought it up was that the transformer isolates everything from DC testing (like resisitance) but still allows current of the alternating type to flow through.

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Quote:
Originally Posted by BobearQSI
They usually convert AC current to DC and/or AC current of a lower value.
Transformers are always AC to AC devices
When I said 'They' I meant 'SMPSes.' Re-read as 'SMPSes usually convert AC current to DC and/or AC current of a lower value.' Although, technically, the SMPS I've seen that outputs AC and DC, the AC didn't go throught much more than a transformer, so the AC output side wasn't really going through the SMPS.
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Old 12-05-2008, 03:54 PM   #58
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Will reverse polarity trip breaker??


Duane,

I've replaced wire behind a wall before, although it wasn't power wire, my technique may work for you. Is the wall straight from the switch to the socket?

Here's what I did: completely disconnect the existing wire from both sides. Tie the new wire to one end of the old one. MAKE SURE YOU TIE IT GOOD. Also, you probably can't have a big knot in it. You'll have to figure out some way to connect the wires up and secure them so that when you pull on them hard, they don't come apart. Maybe something like this with each individual strand: http://www.tollesburysc.co.uk/Knots/Carrick_bend.htm and leave more space to wind the wire around itself for better holding, or figure something out, then wrap it all in electrical tape, etc. Next, pull the other end of the wire out of the wall so that you pull the old wire out of the wall and the new wire through the wall.

That's the tricky part - you don't know how small any holes the wire will go through are. Plus, you have to make sure the tied part does not come apart half way through - if it does, you're really SOL.

Once you get the new wire through (make sure it is overly long), cut off the excess and reconnect everything, now with a proper ground.

I'm assuming since you're posting on a DIY forum, that you'd rather get around hiring an electrician if possible. So this is one option that worked for me before, but you do run the risk of the wire disconnecting in the middle, and the smaller any holes inside the wall are or turns, etc, will make it more difficult. And make sure you wire the new socket correctly as well.
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Old 12-05-2008, 04:49 PM   #59
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Will reverse polarity trip breaker??


I agree with what Gigs said. Call a a real electrician to have your entire house checked out.
You don't know how many other circuits you have wired some crazy way that is just a fire waiting to happen.
Seeing that bare ground wire in the NM used as a hot would have caused me to immediately begin checking every receptacle, switch, light, and anything else that uses electricity in the house.

My burning question: Why in Hell did the guy who wired this use the bare wire as a hot?
It would have made at least a tiny bit of sense (but still be way off being code) if he had used the black and white as the hots, and the bare wire as neutral.
If I could find out who wired your house, I would file a lawsuit today! Then of course, the guy would vehemently deny that he did any wiring, and no one could prove he did.

One further note: Since you have no ground on the receptacle for the TV, you should probably install a GFCI just to be safe.
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Old 12-05-2008, 06:57 PM   #60
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Will reverse polarity trip breaker??


Thanks again guys. I have already replaced all of the outlets and switches in the house and all appreared to be wired correctly. The reason I replaced everything was because the outlets were back-stabbed and I'm sure all of youl electricians know what happens to back-stabbed connections after a few years. I had a bedroom circuit quite working because of a loose back stab connection. Then the wife decided she wanted white outlets/switches instead of almond - so everything got changed. I didn't find anything like the ground wire fiasco in the switch box for the TV outlet. Yes, probably a good idea to up a GFCI in the TV outlet box now.

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