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Bathroom light was flickering, then out. Circuit tester shows Hot/Grd. reverse.

Bathroom light was flickering, then out. Circuit tester shows Hot/Grd. reverse.

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  #1  
Old 02-05-11, 09:05 AM
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Bathroom light was flickering, then out. Circuit tester shows Hot/Grd. reverse.

A little history but brief. We have been in this house 5 yrs., no changes to this bathroom circuit. 3 weeks ago vanity light bulbs began intermittently flickering. Then one burned out. A few days later nothing in the bathroom worked.

This circuit powers the bathroom GFCI outlet, light, fan, and one outlet in another room. I used a plug-in tester in the outlet(s) that shows HOT/GRD reverse. I pulled the GFCI outlet and found the line coming from the breaker. When testing with my meter I get 120V from BLK to grd, 14.8V from WHT to grd., and 100V from BLK to WHT. The wiring in the outlet box looks good.

Any recommendations on how to proceed from here? Will I have to trace the line to/from the breaker box? I am just puzzled as to why this would happen out of the blue.

Thanks,
Steve H.
 
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Old 02-05-11, 10:32 AM
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You probably have an open neutral. Are there other fixtures on this circuit? If so the problem will be at the last good or last bad fixture before the receptacle. My guess would be a bad connection at the light.
 
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Old 02-05-11, 10:35 AM
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You'r description suggests a drop of 20 volts in the Neutral ( White wire ) conductor between the outler box where the voltages were read , and the breaker panel.

You need to determine what other outlets are connected to this circuit by switching the breaker off, and then locating all the outlets that were affected by de-energizing the circuit.
 
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Old 02-05-11, 10:57 AM
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Am I correct that there should be NO voltage from Neutral to Grd.? Why would I be getting 14V on the Neutral?

I cannot find any other outlets that have been effected by turning off the breaker. Therefore I am thinking the wiring goes direct from the breaker box to this GFCI outlet box. I will probably have to pull the breaker box cover and trace the wiring thru the box and across the basement as best as possible.

Steve
 
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Old 02-05-11, 11:48 AM
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The 14 volts between the Neutral and Gnd. is the value of a Neutral current X a resistance in the Neutral conductor between the outlet - box and the Neutral temination in the Service panel , say 2 amps X 7 Ohms = 14 volts.

Essentialy , the Neutral conductor , box-to-panel , and the Grounding Conductor , panel to box , are "in series" when you apply the test probes to the ttest -points.

If the Black / White "Feed-In" pair at the outlet-box goes directly to the panel, and to no other outlets , then with Zero current in the open circuit the voltage across the Black / White pair at the box must equal the voltage across these conductors where they terminate in the Service panel

A voltage difference , or drop , indicates current in the conductors.
 
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Old 02-05-11, 12:53 PM
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Am I correct that there should be NO voltage from Neutral to Grd.? Why would I be getting 14V on the Neutral?
The neutral is a current carrying conductor. I wouldn't be surprised to find some volatge on the neutral, but what you have could be just a phantom voltage too. As far as only having 100 volts, hot-to-neutral, you have a bad neutral connection somewhere upstream in the circuit, I've seen it many times. I would be checking for poor back stab connections at devices as well as checking all wire nutted connections between the device and the service panel. Check the neutral connection at the neutral bus in the panel too.

Those plug in testers can be useful at times, but don't trust them 100% of the time without their results being confirmed with a real piece of test equipment.
 
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Old 02-05-11, 07:58 PM
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Smile

Well I think that I got it. Knock on wood...

I was able to figure out which neutral and ground in the breaker panel were for that circuit. The neutral connection at the bus was a bit loose - I was able to tighten the connection screw a 1/4 turn. That seems to have done the trick.

I rechecked voltages coming into the outlet box from the panel. I have 120V Hot to grd., 120V Hot to Neutral, 0V from neutral to grd.

Hopefully that's all it was.

Thanks for all of the ideas. I will post back if anything changes.

Steve
 
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Old 02-05-11, 08:25 PM
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Good catch. Thanks for letting us know how it worked out.
 
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Old 02-07-11, 07:44 PM
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Wgukew ti===
While you are at it, you might as well tighten (to better clean the connection, loosen it a quarter turn and then retighten) all of the screws and set screws holding the neutral and ground wires in the panel. Also the wires on the circuit breakers, swithc each breaker off when tightening.

NEVER!! Try to tighten the screws on the MAIN BREAKER. Always turn off the main breaker before tightening any other screw. Always turn off branch circuit breaker before tightning. Remember there are "HOT" parts even with the main breaker off
 

Last edited by ray2047; 02-07-11 at 09:37 PM. Reason: For reasons of safety
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