Circuit Tester Causes Backfeed

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  #1  
Old 05-29-02, 09:32 AM
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leelaw
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Circuit Tester Causes Backfeed

I am troubleshooting a non working outside GFI outlet.
The outlet tests at 125V with no load, 64V with load. I've purchased two plug in testers and both indicate reverse hot/neutral. I checked the wiring of the outlet and it is correct. Additionally, when I plug in one of the testers, my electric company provided security light begins to buzz like it is coming on. It is located before the breaker panel and meter.

This outlet is on a circuit with 3 regular outlets (inside the house and not GFI protected) and two switched lights. 1 switch controls an indoor flourescant light, while the other switch controls two outdoor porch lights.

The GFI outlet seems to be the last in the circuit as there are only three wires leading into it (Black, White, Bare).

I've checked all the outlets and they all read normal with the test. Everything seems connected good as well, even though the outlets are using the "backstab" holes instead of the lugs. I've taken the fixtures apart and checked the connections and all seems fine.

I'm not an electrician, so I'm not familiar with how the switch wiring should be. Someone suggested that the GFI was somehow connected with a switch loop.

Another person told me to check the breaker panel and tighten the neutrals. I've done this, even though it didn't seem like any of the neutrals were loose.

I have replaced the GFI outlet with a new one.

This outlet has never worked.
 
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  #2  
Old 05-29-02, 12:08 PM
J
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The outlet tests at 125V with no load, 64V with load.
What is the load you tested with, and how did you conduct the test?
I checked the wiring of the outlet and it is correct.
Do you mean that the black wire is connected to the brass screw and the white wire is connected to the silver screw, both on the "load" side of the receptacle?
Everything seems connected good as well.
Do you mean that you have verified that at every outlet on this circuit, all blacks are connected to brass and all whites are connected to silver (or the backstab holes adjacent to those screws)?
Someone suggested that the GFI was somehow connected with a switch loop.
Tell us about everything on this circuit that is controlled by a switch, and what that switch controls.

Have you or anyone else made any recent wiring changes? Do you have reason to suspect that some of this wiring may have been done by an unqualified person?

It sounds like someone may have tried to add a receptacle to a switch that was wired with a switch loop. Are any receptacles on this circuit in the same box (or in a nearby box) as a switch? If so, what does this switch control?
 
  #3  
Old 05-29-02, 12:38 PM
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leelaw
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Quote: The outlet tests at 125V with no load, 64V with load.
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What is the load you tested with, and how did you conduct the test?
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***I tested with a 60 watt table lamp plugged in with the plug slightly out so I could insert the multimeter probes in behind the plug to touch the plug prongs.



quote:
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I checked the wiring of the outlet and it is correct.
--------------------------------------------------------------------------------
Do you mean that the black wire is connected to the brass screw and the white wire is connected to the silver screw, both on the "load" side of the receptacle?


***Yes, the black wire is connected to the side of the GFI that says black and the white is connected to the side that says white.



quote:
--------------------------------------------------------------------------------
Everything seems connected good as well.
--------------------------------------------------------------------------------

Do you mean that you have verified that at every outlet on this circuit, all blacks are connected to brass and all whites are connected to silver (or the backstab holes adjacent to those screws)?

***Yes, I have taken each outlet out and checked the wiring, I even took a couple of them out of the backstabs and attached them with the screws. I also tested each outlet with the plug in tester, all of which tested good.




quote:
--------------------------------------------------------------------------------
Someone suggested that the GFI was somehow connected with a switch loop.
--------------------------------------------------------------------------------

Tell us about everything on this circuit that is controlled by a switch, and what that switch controls.



***There are only 2 switched devices on this circuit. 1 switch controls a flourescant light in a closet, the other controls 2 outside porch lights.




Have you or anyone else made any recent wiring changes? Do you have reason to suspect that some of this wiring may have been done by an unqualified person?

***No wiring changes. It is existing wiring. The wiring was done about 10 years ago by me and my father who is a contractor and was inspected by the local inspector. For the first few years, we never used the outside outlet, so when I first tried a couple of years ago, I assumed the GFI had gone bad.


It sounds like someone may have tried to add a receptacle to a switch that was wired with a switch loop. Are any receptacles on this circuit in the same box (or in a nearby box) as a switch? If so, what does this switch control?

***No, only 3 unswitched outlets (not counting the outside GFI) and 2 switches (1 for closet light, 1 for 2 outside porch)

I've also been reading about the off the shelf consumer grade testers and their reliability. Which from what I've read are not always reliable. Would a pro model provide better information?
 
  #4  
Old 05-29-02, 04:06 PM
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Wgoodrich
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Everything you are saying is suggesting a loose connection. Power when no load with a connection barely touching, but loss of power when under load connection not good enough contact to maintain connection under load.

Check for a wire in a wire nut that didn't make it in the wire nut as it should have. Pull on each individual wire on each wire nut.

Then check bad connection where the spring clip in the back stab receptacle has lost tension. I think this is your real culprit. Somewhere on that circuit you probably will find a back stab with a failed sprng connection in the back of that receptacle.

Turn off that branch circuit in the panel and check each receptacle for a bad spring connection back stab that is off with that breaker off.

Good Luck

Wg
 
  #5  
Old 05-29-02, 04:09 PM
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Wg is right about a loose connection........I'd look really hard at the neutral wires because of your comment that voltage drops to 64 volts and your other light buzzes like it wants to come on
 
  #6  
Old 05-29-02, 04:44 PM
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leelaw
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Thanks for all the great advice. I've taken all the backstabbed leads and screwed them on instead.

I got a bright idea to use my continuity tester.

With circuit powered off (of course), I inserted the test leads into an outlet. And I have continuity.

I had left the outside porch lites on so I would know the circuit was dead.

Flip the switch off, no continuity.

I suspect that I should have no continuity between the hot and neutral legs, and the switch is miswired somehow.
Now my problem is figuring out how to wire that switch. It controls two lights. One light has 4 cables coming into it.
Below are my assumptions on what they do.
#1 cable - Feed from box or power source
#2 cable - Switch leg
#3 cable - Feed to 2nd light
#4 cable - I have no clue unless it's feeding the rest of the circuit.

Of course these cables are not labeled in this manner so I'm not sure which one does what.
 
  #7  
Old 05-29-02, 06:11 PM
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leelaw
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Does this look like the proper wiring?


 
  #8  
Old 05-29-02, 06:29 PM
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Wgoodrich
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Absolutely not. YOu are switching your grounded leg instead of your hot conductor in your drawing that is against the rules of the NEC. A grounded leg [aka neutral conductor] must not be switched. Your black of switch leg should be connected to the two blacks of the light and the white of your swtich leg should be connected to your black power in and power out. All the rest of the whites must be wire nutted together under one wire nut.

You may be misidentifying one of these wires causing a series wiring affect to your outside receptacle. This would create a false reading on your continuity tester leading you down the wrong path for diagnosis reading a grounded leg through the filament of your light bulb to ground.

I am convinced you either have a loose white wire in one of your receptacles or in a wire nut. You need to correct your switch box wiring as discribed above. Then start over in your test of that receptacle. If you still have a dead receptacle under load then go back to your back stab connections of receptacles or a loose wire nut. As Mike 134 suggested I too suspect a bad connection of a white grounded leg [aka neutral] plus a bad and unsafe wiring design in your switch box.

Wg
 
  #9  
Old 05-29-02, 07:07 PM
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leelaw
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Would this wiring configuration cause the circuit tester reading to indicate reverse hot/neutral? And also cause the tester to create a backfeed out to the security light?

I have pulled all the wires from the outlets and secured them with the screws. There is only one other switch on this circuit, a florescent fixture, that also creates continuity in an outlet when switched on.

I checked some of the other switches in the house and they are wired as you said. I don't know why this particular arrangement was used.

Everyone's input and advice has been greatly appreciated!! I think I'm going to call an electrician tomorrow, though, as it looks like this may be getting too complicated for me.
 
  #10  
Old 05-29-02, 08:26 PM
J
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Ah, the picture is very clear now!!

You have incorrectly labeled the cables in your diagram. The labels "AC in" and "Switch" are reversed. Try reversing the labels. Then your light is correctly switched, and is wired in the normal manner according to code.

This also explains the reversed polarity. Since the cable you labeled "Switch" is actually the power source, you can see how the black from this cable is connected to the white from the "AC out" cable, and the white from the power cable is connected (through the bulb filiment) to the black from the "AC out" cable. This also explains the 64 volts, since the light bulb is in series with the "AC out" cable.

This explains absolutely all the information you have presented!

The problem can be corrected by reconnecting the "AC out" and the "Feed to the 2nd light" to the like colors on the power cable (which is incorrectly labeled "Switch" in your diagram). Note: if the "feed to the 2nd light" is supposed to be a switched feed, you can leave it connect as it is now. However, the "AC out" cable should definitely be reconnected directly to the power cable.

I'm pretty confident of this explanation.

P.S. Your continuity test is as expected. You got continuity through the filiment of the lightbulb. No great surprise there.
 
  #11  
Old 05-30-02, 04:56 AM
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leelaw
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I can't eat, I can't sleep, I can't even get any work done until I solve this problem. I'm obsessed with it now.

(Note that wife left me this morning: I heard something growl in the lawn on the way to the car this morning, please call the electrician, and MOW THE YARD.)

I have verified the switch leg by removing all the connections, and using the continuity tester. With the switch on, the only pair that I got continuity on was the one listed. From there I verified the feed to the second light by putting in the the bulb and testing continuity. The Feed out (AC Out) to other receptacles I verfied by putting a jumper across the hot and neutral of an indoor receptacle on this circuit. This left the AC In Cable. Now whether this is a direct feed from the box or another receptacle/light, I'm not sure. I can't seem to find anything else that isn't working while this circuit is off. ******(((NOTE TO OTHER DO IT YOURSELFERS- DOCUMENT EACH AND EVERY CONNECTION ON THE CIRCUIT!!!)))******
I then followed WG's instructions for wiring the junction. Still I get the hot/neutral reversed reading.

So then I get the bright idea to bypass the porch lites altogether. I take AC In black and connect to AC Out black, same for the white. I test the GFI again and this time my circuit tester indicates "Hot on neutral W/open neutral".

There's one more place to look for an additional connection to this circuit. It's up in the overhead crawlspace.

Then I'm out to mow the yard.
 
  #12  
Old 05-30-02, 07:41 PM
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leelaw
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I DID IT!!!!

I can sleep now. And even get some work done.

Got to thinkin, why aren't there switch wires in the flourescent light? Hmmmmm,....

JUNCTION BOX OVERHEAD.

Looks like I've got it.

Lemme make sure I've got this right... Switches are wired hot.


Thanks Again for everyone's input.
 
  #13  
Old 05-30-02, 09:26 PM
J
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And the yard's looking good too?
 
  #14  
Old 05-31-02, 06:50 PM
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leelaw
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And the yard looks good too!!


I've gotten everything back together and the outlet is working fine and all the lights and outlets on the circuit are working as well. But there is one peculiar thing. I bought 2 testers the other day at Lowes. One a Sperry Instruments circuit tester for GFCI outlets with the 3 neon lights and test trip button. When using this tester on the previously troublesome GFCI outlet, it indicates 2 yellow lights, which is everything is okay. And the trip button trips it. But when I use the other, a Sperry Instruments "Stop Shock", which does not have the GFCI trip button, it indicates defective ground. Which of these testers are telling the truth.

BTW, when using the "Stop Shock" tester, my security light still buzzes.

Thanks All!
 
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