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voltage present when power is turned off??? #1770
05/29/01 09:20 PM
05/29/01 09:20 PM
S
smokey  Offline OP
Member
Joined: Apr 2001
Posts: 41
cctxusa
out on a job once i remember sticking my meter to check for voltage and all i was reading was 6.6v between ungrounded conductor(hot) and the grounded conductor (neutral) on the receptacle with the breaker feeding the circuit turned off.. where was this mysterious voltage coming from??? could it have been a backfeed of some sort???

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Re: voltage present when power is turned off??? #1771
05/29/01 09:22 PM
05/29/01 09:22 PM
S
sparky  Offline
Member
Joined: Oct 2000
Posts: 5,360
smokey;
it's probably induction, you could flip breakers until the culprit was found.

Re: voltage present when power is turned off??? #1772
05/30/01 10:00 PM
05/30/01 10:00 PM
S
smokey  Offline OP
Member
Joined: Apr 2001
Posts: 41
cctxusa
thanks sparky

Re: voltage present when power is turned off??? #1773
06/01/01 07:32 AM
06/01/01 07:32 AM
electure  Offline

Member
Joined: Dec 2000
Posts: 4,274
Fullerton, CA USA
I still carry my old solenoid Wiggy with me, as well as my digital tester. The Wiggy puts enough load on the wire being tested to zero out these induced readings (try them both at once = 0). You can get some pretty high readings w/ the digital on long homeruns @ 277/480.

Re: voltage present when power is turned off??? #1774
06/01/01 01:18 PM
06/01/01 01:18 PM
sparky66wv  Offline
Member
Joined: Nov 2000
Posts: 2,236
West Virginia
Sans Wiggy, I have put a resistor (light bulb on a pig tail) between the same two points and then measure the voltage. The connection to ground tends to "bond" any stray voltage...I think. If it reads 0 volts set up this way, then no worries...if the bulb burns, you have a short. I'm sure the wattage of the bulb comes into play here too for any resisted shorts that would complicate the issue.

I'm asking opinions here rather than suggesting this method. It's sort of a "poor man's" troubleshooting trick, but I'd like to know all the "druthers" involved... Any comments?


-Virgil
Residential/Commercial Inspector
5 Star Inspections
Member IAEI
Re: voltage present when power is turned off??? #1775
06/01/01 08:20 PM
06/01/01 08:20 PM
Joe Tedesco  Offline
Member
Joined: Oct 2000
Posts: 2,749
Boston, Massachusetts USA
Look for the report at www.nema.org

[This message has been edited by Joe Tedesco (edited 01-09-2003).]


Joe Tedesco, NEC Consultant

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