Greetings and Puzzling Electrical Problem

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  #1  
Old 10-10-03, 09:41 AM
Jon_sparky
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Question Greetings and Puzzling Electrical Problem

Hi,
Greetings! I am new to this forum, just a few things about myself.
I have been a electrician for 20 years and have my own buisness since 1986.
I have a very interesting electrical problem, one that i never incountered before...
I am working in a Nunnery, it was wired in 1968 in steel flex. I was working in one of the bathrooms, where there is a thermador wall heater, I am moving a timer for the heater that was to close to the bathtub. I identify the circuit in a nearby sub-panel and turn it off. This is where it gets interesting; The voltage is still present in the circuit, after the breaker is opened the voltage drops to 32 volts! It is a split circuit sharing the nuetral with a receptical circuit. When I turn off the other breaker the 32 Volts drops to 0 V. I haven't had a chance to go into the bedrooms yet to open everything up, and check it out.
Does anyone have any idea what is going on??? The nuetral is solid to the panel, as the other circuit is 120V from hot to nuetral. Jon
 
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  #2  
Old 10-10-03, 01:37 PM
winkleal
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Are you using a Digital multimeter to measure the voltage? If so, you are not putting enough load on the circuit to drop the voltage. If you were to use an analog meter, my money is on that it would register close to zero volts while the other circuit is on.

DMM tend to read funny sometimes due to the fact that the internal resistance is so high.

Tony
 
  #3  
Old 10-10-03, 04:27 PM
Jon_sparky
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You were right!
That was my first thought too. The thing that threw us was that the Fluke Voltage alert showed power present.
I checked it with my Fluke 12 DMM with a function called V check, this will check for "real " power. This meter read 1.63 VAC i still don't know where this voltage is leaking in from... Maybe it is transients on the nuetral?
Thanks for the help, saved me from opening up all those receptical boxes!!!
Jon
 
  #4  
Old 10-10-03, 05:05 PM
winkleal
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The 1.63 V you are still seeing is probably due to the current still flowing on the neutral from the circuit that is energized. Your reference is the bare wire, which has "no current" and the wire you are testing has a current flowing through it. You are measurung the voltage drop of the neutral wire from the test point to the panel. (approximately) To test this theory, turn off different loads on the other circuit and see if the voltage changes.

Remember, wire has a resistance. That is my theory on why you are seeing the voltage when the circuit you are working on in turned off.

Tony
 
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Old 10-10-03, 09:23 PM
Jon_sparky
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Thanks for the input! You are probably right about the the return voltage on the nuetral wire, I will check it next week and post the findings... Jon
 
  #6  
Old 10-11-03, 10:01 PM
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I have also had some DMM problems where the wiring is not able to be traced easily, and there are problems requiring troubleshooting. Especially when the grounding is not 100%, and/or the circuit has the nuetral accidenlty tied into another circuit. gj
 
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