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-   -   Will reverse polarity trip breaker?? (http://www.diychatroom.com/f18/will-reverse-polarity-trip-breaker-33021/)

Duane 70 12-02-2008 12:48 PM

Will reverse polarity trip breaker??
 
Our kids just bought us a new LCD HD TV. We plugged it into the same switched receptacle used by the old TV for 6 yrs. with no problems. Started to connect the TV cable and got shocked - thought what the f---!!! Unplugged it and hooked up the cable. Plugged it in, turned it on and the breaker (15 amp) tripped after about 4-5 seconds. Took TV back to store and got another one (same model). Tried hooking up again - no shock this time but still tripped breaker. Took TV back to store and went to another store and bought a different brand/model. Hooked up, turned on, still tripped breaker - what the f---??? Brother-in-Law said sounds like the polarity may be reversed. Get multimeter and check other outlets for correct polarity. Other circuts tested correct. Run extension cord from correctly wired outlet to TV, turned on, works good. So I reversed the wiring on the TV receptacle, disconnected the switch and tried the TV again - works good. Tested the other outlets on the same circut and they all test correct polarity. What is going on? Did builder/electrician somehow get the wiring reversed somewhere on the switched outlet? All wires I can see seem to be connected correctly. Do the new TVs require correct polarity to work? Why would the breaker trip? Wouldn't the TV have to be pulling more than 15 amps? Would reverse polarity cause that - somehow a dead short??? Thanks for any suggestions/ideas.

J. V. 12-02-2008 01:42 PM

How did you check polarity with a multimeter and 120 volt ac circuit. You can determine the hot from the neutral though. Is the white (neutral) on the silver colored screws on the receptacle? Check the white to ground and the hot to ground to check correct connection of the receptacle. You say the recept is switched? If so the switch leg wire may be white. Do not use the switched side of the recept for the TV. Use the continous hot (usually the top).
Can you plug something else into this recept. and see if it is working correctly? Since the old set worked fine on this recept, it is something of a mistery to me. I am not sure that polarity is the issue, but it could be. What is the current rating of the TV? Is this a big screen TV?

KE2KB 12-02-2008 02:15 PM

It wouldn't just happen that the 15A breaker your TV is connected to is a GFCI, is it?
If so, the TV will trip the breaker when the polarity is wrong, because there is leakage through capacitance to ground. It is a normal thing for TV to have this.
That said, if the breaker is not GFCI, there is a problem. I cannot imagine for an instant that UL would approve any appliance that would, when plugged into an improperly wired receptacle allow the user to get a shock for any reason.
Connecting the cable or antenna to a TV should never give someone a shock!
That said, did you experience a "full" 115V shock, or was it less than that?
Also, was there a big spark when you touched the CATV line to the TV?
If there were enough current to trip a 15A breaker (even after a few minutes), you would see a large spark.

When I lived in my apartment, I was getting a small amount of current through me when I was hooking up the cable TV to the television. This happened because the STB (set top box) had surge suppressors in it, and there was a small amount of current (far from what would have hurt me) flowing through the CATV shield to ground.
This would most likely have tripped a GFCI, but none was installed.

If I were you, I would disconnect the CATV/Sat line from the TV, and measure the potential between it and the ground (not neutral) of a known-good receptacle.
There should never be 110V there. You may get a reading of between 25V and 40V, but that's as much as I would ever tolerate being on that line.

Yoyizit 12-02-2008 02:35 PM

Quote:

Originally Posted by Duane 70 (Post 192780)
the breaker (15 amp)
tripped after about 4-5 seconds.
So ~45A flowed.
Probably your coax cable shield and cable insulation is damaged.

I assume the TVs have ground pins in their plugs.

rgsgww 12-02-2008 03:03 PM

How old is the wiring in this house?

Can you post pics of the culprit outlet?

Duane 70 12-02-2008 03:19 PM

Thanks for the replies. First, the outlet/circut is not on GFCI. The wires were connected originally black wire to gold screw/white wire to silver screw. I know everything is connected correctly in the breaker panel because we just an electrician put in a new panel and breakers last year to replace an old Zinsco setup. I watched everything he did and all blacks (120v lines) are connected to the breakers and all whites to the neutral bar w/all grounds to the ground bar. Yes, on the first set, there was a good shock and spark - like 120v type. I switched the wire on the outlet to white on gold and black on silver and the TV works OK. I actualy replaced the receptacle with a new one and removed the wire from the switch so the outlet is no longer switched, just straight wired with the rest of the circut. Strangely, the rest of the outlets on this circut are wired correctly. I tested this with a multimeter set on 200 volts and tested between hot an neutral (118 v), between hot and ground (118 v) and between neutral and ground (0 v) on the all the outlets. The house is 30 years old and all circuts except one show ground connected. The outlet that was switched for the TV did not show a ground even though it has a ground wire connected to it. Not sure where it goes but it seems if the rest of the outlets on this circut have ground then the switched outlet should also have had ground but appeared not to. I guess my terminology is wrong. When I say I checked the polarity, I mean I checked the correct positioning of the hot and neutral wires. Does anyone know if that would cause a TV (40" LCD HD) to not work or trip the breaker if the wiring is reversed? Sounds odd to me. Haven't encountered any problems since I switched the wires around. Any more ideas on this???

jbfan 12-02-2008 04:48 PM

If you have the black wire on the silver screw, then you have the receptacle wired incorrectly.
You need to trace this circuit out and find where the mix up is located and fix it.

KE2KB 12-02-2008 06:10 PM

Quote:

Originally Posted by jbfan (Post 192861)
If you have the black wire on the silver screw, then you have the receptacle wired incorrectly.
You need to trace this circuit out and find where the mix up is located and fix it.

Exactly! One of the upstream receptacles has it's downstream wiring connected incorrectly.
Perhaps at the now removed switch?

Duane 70 12-02-2008 06:46 PM

That's what I don't understand. The rest of the outlets on this circut are wired correctly, black to gold, white to silver. The switched outlet was also black to gold and white to silver when it was tripping the breaker. Had to change that outlet to black to silver and white to gold to get the TV to work. I'm thinking it has to be with the switch somewhere - except the switch is now disconnected and the TV still works with black to silver and white to gold. Also, why would the breaker trip with reversed wiring? Wouldn't it have to be pulling more than 15 amps? What would cause this with just the wiring reversed and why would the original TV work without any problems for 6 years??

Duane 70 12-03-2008 08:01 AM

I guess my main question is why the outlet/circuit worked fine with my old TV (37" tube set) for so many years, but tripped the breaker with the new LCD 40" set? The only difference that I can see is that the old set did not have a ground wire in the cord, where the new set has a ground wire/plug prong in the cord. Are the new TVs electronics so sensitive that reversed wiring in an outlet would trip a 15 amp breaker? I'm not so sure that reversed wiring is the problem. The wires were correct when I pulled the outlet (black to gold, white to silver) as well as all of the other outlets on the some circuit. After reversing the wires on the TV outlet, the TV works OK. 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? If it was a switch to outlet wiring problem, wouldn't that already have caused the breaker to trip with the old TV?? I haven't tried putting the wires on the outlet back in their correct locations because I hate to take a chance on screwing something up in the TV if it trips the breaker again by doing that since it works OK now as is. Just can't figure out why reversed wiring would cause the breaker to trip. Any takers on this puzzle??

rgsgww 12-03-2008 08:21 AM

Quote:

Originally Posted by Duane 70 (Post 193141)
I guess my main question is why the outlet/circuit worked fine with my old TV (37" tube set) for so many years, but tripped the breaker with the new LCD 40" set? The only difference that I can see is that the old set did not have a ground wire in the cord, where the new set has a ground wire/plug prong in the cord. Are the new TVs electronics so sensitive that reversed wiring in an outlet would trip a 15 amp breaker? I'm not so sure that reversed wiring is the problem. The wires were correct when I pulled the outlet (black to gold, white to silver) as well as all of the other outlets on the some circuit. After reversing the wires on the TV outlet, the TV works OK. 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? If it was a switch to outlet wiring problem, wouldn't that already have caused the breaker to trip with the old TV?? I haven't tried putting the wires on the outlet back in their correct locations because I hate to take a chance on screwing something up in the TV if it trips the breaker again by doing that since it works OK now as is. Just can't figure out why reversed wiring would cause the breaker to trip. Any takers on this puzzle??

Hmmm...Something isn't wired right. I wouldn't leave it like it is because this is a hazard.

Check any junctions. Find the cable going to that outlet, disconnect it, test resistance between ground and neutral, hot and neutral and hot and ground.

Stubbie 12-03-2008 11:52 AM

Duane

Please check the tv coax ground shield for voltage...you got shocked to the tune of 120 volts you said. This didn't magically go away by reversing the wires on the receptacle. When you unplugged the new tv with grounded cord you were able to connect the tv coax to the tv. Then when you plugged it back in it tripped the breaker.

rgsgww 12-03-2008 11:54 AM

Check the coaxial shield...forgot about that. Im thinking the voltage may be present on the coax.

Duane 70 12-03-2008 12:03 PM

Obviously I am not an electrician, nor I play one on the internet, but why wouldn't the problem expose itself with the old TV that was plugged into that same outlet and the same cable for 6 years (we just bought the house six years ago) and have had other things (vac. sweeper, Christmas tree lights, etc) plugged into it with no problems. Could it possibly be that a ground was connected incorrectly somehow, somewhere with that switched outlet setup since the other previous things plugged into it didn't have a ground wire in the cord plug?? Just seems totally strange occurrance to me.

rgsgww 12-03-2008 12:10 PM

Quote:

Originally Posted by Duane 70 (Post 193235)
Obviously I am not an electrician, nor I play one on the internet, but why wouldn't the problem expose itself with the old TV that was plugged into that same outlet and the same cable for 6 years (we just bought the house six years ago) and have had other things (vac. sweeper, Christmas tree lights, etc) plugged into it with no problems. Could it possibly be that a ground was connected incorrectly somehow, somewhere with that switched outlet setup since the other previous things plugged into it didn't have a ground wire in the cord plug?? Just seems totally strange occurrance to me.


Seems like a ground may be installed incorrectly. Eliminate all junction points until you find the problem.


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