Multiple circuits affect a single non-working outlet?

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Old 08-15-10, 12:30 PM
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Question Multiple circuits affect a single non-working outlet?

Introduction
My townhouse has a wall-mounted exterior electrical outlet that, to put it simply, does not work. The outlet is a Leviton 15-Amp White Self Grounding Duplex Power Outlet. A "weatherproof" outlet cover, like this Greenfield Duplex Weatherproof Electrical Outlet Cover, protects the outlet.

Caveat lector
I am an amateur. I have accomplished relatively simple electrical work, such as replacing electrical outlets and installing ceiling fans and light fixtures. I have no relevant formal training, though.

Tools
  1. RadioShack "GFCI TESTER"
  2. DT-5806 digital multimeter

Actions and Observations
I discovered the problem when the outlet failed to power a tool that I'd plugged into it.

I checked both plugs of the outlet using the RadioShack GFCI tester, which indicated no reading for either plug. I interpreted this lack of reading as insufficient voltage.

I checked both plugs of the outlet using the DT-5806, which indicated approximately 4.5 VAC between conductor and ground. All circuits had been enabled at the circuit breaker panel. This low voltage reading struck me as very odd (and induced some heebie-jeebies ).

I decided to uncover the outlet for closer inspection. Before removing the outlet's cover, I decided to try to zero the DT-5806 voltage reading. While my wife monitored the voltage reading, I disabled one electrical circuit at a time. No single circuit-disablement zeroed the voltage reading, but several single circuit-disablements reduced the voltage reading. By disabling four (yes, four!) particular circuits, we minimized the voltage reading at approximately 0.7 VAC. (This added "the willies" to my heebie-jeebies. )

Phantom voltage? Stray voltage?
Before posting this message, I searched this forum. A reply in another thread in this forum cautioned the thread's original poster, who (like me) used a digital multimeter, that phantom voltage (or stray voltage) can mislead. I found NEMA Engineering Department Bulletin No. 88 (October 1998; Revised February 2003) educational.

Guesses
I guess that this electrical outlet has an open circuit that is capacitively-coupled with powered circuits, somewhere between the outlet and the circuit breaker panel (about 30 feet away), and that my digital multimeter reads the induced phantom voltage.

Questions
  1. Do you think that my digital multimeter is reading phantom (stray) voltage?
  2. What causes, other than phantom voltage, can account for the low voltage readings?
  3. Should I obtain and use a solenoid voltmeter, such as the Wiggy, to continue troubleshooting this electrical outlet?
  4. What do you recommend I do with this problem?
 
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Old 08-15-10, 01:06 PM
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You need to look for a GFCI outlet that has tripped. These will look like a normal out with two button in the middle. They will be either in your bathrooms, garage, or even another outdoor receptacle.

You need to reset this device...
 
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Old 08-15-10, 01:19 PM
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I strongly recommend that amateurs use a solenoid-type tester because it is immune to phantom voltages. And yes, it IS phantom voltage that you are reading and having to turn off multiple circuits to lower or dismiss the phantom reading is completely normal.

Hot is correct that "somewhere" you have a GFCI receptacle that feeds power to this outside receptacle...unless the receptacle was installed by an unknowing previous homeowner. In my own home I found the related GFCI receptacle in the garage but with a "six outlet adapter" covering the test and reset buttons.
 
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Old 08-15-10, 01:22 PM
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Originally Posted by HotinOKC View Post
You need to look for a GFCI outlet that has tripped. ... You need to reset this device.
@HotinOKC: I reset my house's two GFCI outlets and re-checked the voltage; the voltage remains approximately 4.5 VAC, and the problem persists. Thanks.
 
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Old 08-15-10, 01:38 PM
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Originally Posted by furd View Post
I strongly recommend that amateurs use a solenoid-type tester because it is immune to phantom voltages. And yes, it IS phantom voltage that you are reading and having to turn off multiple circuits to lower or dismiss the phantom reading is completely normal.
@furd: Thanks for confirming my guess about the phantom voltage. I will obtain and use a solenoid voltmeter.

Originally Posted by furd View Post
Hot is correct that "somewhere" you have a GFCI receptacle that feeds power to this outside receptacle...unless the receptacle was installed by an unknowing previous homeowner. In my own home I found the related GFCI receptacle in the garage but with a "six outlet adapter" covering the test and reset buttons.
As far as I know, my house has only two GFCI outlets: one in the upstairs bathroom, and one in the laundry room. The outlets share the same circuit. My house has no garage or outbuildings; it does have a utility closet that contains the HVAC equipment and sump-pump, but no GFCI.

Both of the two GFCI outlets did their "CI" thing on the day I tried to troubleshoot the exterior electrical outlet, probably during my circuit-disablements. I reset both of the GFCI outlets and re-checked the exterior outlet. The problem persists.

@furd: Any more thoughts? Thanks for your time and advice.
 
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Old 08-15-10, 01:55 PM
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Over time we have posters who swore they had tested all the GFCI receptacles after days of testing they found another GFCI behind a piece of furniture, behid a box in a storage area or in an unexpected place like an attic or crawl space.

If it isn't a GFCI then it is probably a bad connection either at the last good receptacle or first bad receptacle. All wires in back stabs should be moved to the screws. Any wire nuts should be removed and checked for corrosion or loose wires. Bad connections can also occur in switch boxes and ceiling boxes.

If this is a condo you may have an accidentally shared circuit with a neighbor, not likely but it happens. Of course if you aren't the owner legally you can't do any work on the electrical.
 
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Old 08-15-10, 03:04 PM
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Originally Posted by Three_Oh_Five View Post
[*]Do you think that my digital multimeter is reading phantom (stray) voltage?
Yes.

Originally Posted by Three_Oh_Five View Post
[*]What causes, other than phantom voltage, can account for the low voltage readings?
None. Phantom voltage is caused by other conductors next to the circuit you are working on. The voltage in induced by the other conductors.

Originally Posted by Three_Oh_Five View Post
[*]Should I obtain and use a such as solenoid voltmeter to continue troubleshooting this electrical outlet?
That or buy a quality digital meter. I use a Fluke 7-600 and it blocks pretty much all phantom voltage.

Originally Posted by Three_Oh_Five View Post
[*]What do you recommend I do with this problem?
Keep looking for a hidden GFCI. Places to look are in bathrooms, garages, basements, other outdoor receptacles and the panel for GFCI breakers. Turn off and then on each and every breaker. Also remove the device and take your readings directly from the wires.
 
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Old 08-15-10, 03:08 PM
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Originally Posted by ray2047 View Post
Over time we have posters who swore they had tested all the GFCI receptacles after days of testing they found another GFCI behind a piece of furniture, behid a box in a storage area or in an unexpected place like an attic or crawl space.
@ray2047, et. al.: Fair cop. I will scour my house for GFCI outlets/receptacles!

Originally Posted by ray2047 View Post
If it isn't a GFCI then it is probably a bad connection either at the last good receptacle or first bad receptacle. All wires in back stabs should be moved to the screws. Any wire nuts should be removed and checked for corrosion or loose wires. Bad connections can also occur in switch boxes and ceiling boxes.
@ray2047: I will trace the connections from this outlet to the circuit breaker panel, and deal with each intermediate junction/outlet as you have recommended. Thanks!
 
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Old 08-15-10, 03:16 PM
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Originally Posted by Tolyn Ironhand View Post
Phantom voltage is caused by other conductors next to the circuit you are working on. The voltage in induced by the other conductors.
...
That or buy a quality digital meter. I use a Fluke 7-600 and it blocks pretty much all phantom voltage.
@Tolyn Ironhand: Thanks for confirming my guess about phantom voltage, and for recommending a better digital multimeter.

Originally Posted by Tolyn Ironhand View Post
Keep looking for a hidden GFCI. Places to look are in bathrooms, garages, basements, other outdoor receptacles and the panel for GFCI breakers. Turn off and then on each and every breaker. Also remove the device and take your readings directly from the wires.
@Tolyn Ironhand: I will scour my house for GFCI outlets/receptacles! Thanks!

@Tolyn Ironhand: Why do you recommend that I "turn off and then on each and every breaker"?

@Tolyn Ironhand: As I recall, the voltage readings from the device matched the voltage readings directly from the wires. I had removed the device in order to replace it with a new electrical outlet, since the original outlet showed some rust/corrosion.
 
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Old 08-15-10, 05:17 PM
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Originally Posted by Three_Oh_Five View Post
@Tolyn Ironhand: Why do you recommend that I "turn off and then on each and every breaker"?
Sometimes people miss seeing a tripped breaker. By switching them all off, and then back on, it will reset them.
 
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Old 08-15-10, 05:45 PM
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Originally Posted by Tolyn Ironhand View Post
Sometimes people miss seeing a tripped breaker. By switching them all off, and then back on, it will reset them.
@Tolyn Ironhand: Thanks! That makes sense.
 
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Old 08-15-10, 06:42 PM
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One thing also perhaps needs clarification. You write "multiple circuits". That would mean multiple breakers. Don't you mean multiple outlets* on one breaker? If fixtures on more then one breaker were involved baring unlikely coincidence the cause would be different from the causes we are discussing.

*(An outlet by NEC definition is a point where power can be taken for utilization, e.g. receptacle or light)
 
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Old 08-15-10, 08:33 PM
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Originally Posted by ray2047 View Post
One thing also perhaps needs clarification. You write "multiple circuits". That would mean multiple breakers. Don't you mean multiple outlets* on one breaker? If fixtures on more then one breaker were involved baring unlikely coincidence the cause would be different from the causes we are discussing.

*(An outlet by NEC definition is a point where power can be taken for utilization, e.g. receptacle or light)
@ray2047: Thanks for clarifying terminology with the NEC definition. I did mean imply "multiple [circuit] breakers" when I wrote "Multiple circuits" in the title of my original post, because multiple circuits (multiple breakers) changed the phantom voltage reading I described:
Originally Posted by Three_Oh_Five View Post
No single circuit-disablement zeroed the voltage reading, but several single circuit-disablements reduced the voltage reading. By disabling four (yes, four!) particular circuits, we minimized the voltage reading at approximately 0.7 VAC.
 
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Old 08-15-10, 08:43 PM
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Hey everyone, thanks for your help so far! I really appreciate your time, advice, and sanity-checking.

As I griped to my wife about this problem, she reminded me of some funky/confusing wiring I'd encountered when trying to troubleshoot a non-functioning switch on the interior-side of the same wall on which the troublesome exterior electrical outlet is installed. The switch had been incompletely-wired to the blower for the neighboring gas fireplace. My wife reminded me that the switch's housing had contained some wires that seemed spurious; I need to check whether that exterior outlet should have been wired into that switch's circuit.

So, while I welcome more thoughts from you, I have need to search for GFCIs and to investigate that switch housing before I can provide more details. Thanks!
 
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Old 08-15-10, 09:55 PM
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I did mean imply "multiple [circuit] breakers" when I wrote "Multiple circuits" in the title of my original post, because multiple circuits (multiple breakers) changed the phantom voltage reading I described:
But as you now know the phantom voltage changes are not necessarily relevant to your problem. I'd bet all are on the same circuit.
she reminded me of some funky/confusing wiring I'd encountered when trying to troubleshoot a non-functioning switch on the interior-side of the same wall on which the troublesome exterior electrical outlet is installed. The switch had been incompletely-wired to the blower for the neighboring gas fireplace.
Yep, sounds like the place to start.
 
 

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