ground problem?

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  #1  
Old 10-30-04, 11:25 PM
Daydrmr999
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ground problem?

The original wiring in my home has no ground wire. I've branched off the existing outlets and added a couple new outlets using three wires. now the new outlets show voltage between the hot and ground terminals. Is this normal, and if not, what did I do wrong?

Thanks,

Mike
 
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  #2  
Old 10-31-04, 03:50 AM
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1) How are you measuring this 'voltage'?

2) In the original outlet boxes with only two wires feeding them, what sort of wiring method was used? Old NM cable ('Romex') with only two wires, or AC (metal armor clad) cable with two wires, knob and tube?

3) When extending these circuits with modern three wire NM cable, where did you connect the ground wire at both ends.

4) You should know that it simply does not meet code to install three prong receptacles with out an EGC (ground) conductor that properly goes all the way back to the panel. The only exception is if you are replacing an existing receptacle, and you provide GFCI protection. For these _new_ receptacles, you should run circuits back to the panel.

-Jon
 
  #3  
Old 10-31-04, 10:36 AM
Daydrmr999
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more info

The old wiring is old "romex", two sheethed wires which are each covered in rubber? then weaved cloth?. The ground is simply connected to the grounds on each outlet. The new outlets are for two wire under cabinet lighting so I don't actually need the ground (switched with a plug/switch combo).
And I did add a gfci at the first outlet in the series.
Thanks

Mike
 

Last edited by Daydrmr999; 10-31-04 at 10:38 AM. Reason: added last line
  #4  
Old 10-31-04, 10:51 AM
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You didn't say _how_ you measured the voltage. I am _guessing_ that you used a digital volt meter rather than some sort of low impedance tester.

If my guess about the digital volt meter is correct, then what you describe is entirely normal. You are seeing 'phantom voltage'; search this forum for other cases. I would expect you to also see voltage between the neutral and ground in this case.

If you are actually using a low impedance tester, such as a 'wiggy' or a neon light tester, and you are actually seeing current flow here, then you have a 'bootleg ground' where the neutral wire is shorted to the ground wire. This should be located and repaired.

IMHO your installation is as safe as some things permitted in current code, but it is not code compliant. If you have the option, you should upgrade this circuit back to the panel.

-Jon
 
  #5  
Old 10-31-04, 11:47 AM
Daydrmr999
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analog voltmeter

I'm using an analog voltmeter, I'm getting 125 across both neutral/hot and hot/ground, nothing from neutral to ground.

mike
 
  #6  
Old 10-31-04, 11:53 AM
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Those readings are perfect. Everything is fine.
 
  #7  
Old 10-31-04, 12:20 PM
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Daydrmr999,

Your extension is very possibly not wired correctly, and you probably have a 'bootleg ground'.

As John Nelson says, the voltage readings that you've gotten are exactly what you should be getting from a properly wired receptacle with a proper neutral and ground bond in the panel.

But since the feed to these receptacles is through two wire _without ground_ NM cable, there is a strong suggestion that neutral and ground are improperly connected somewhere in the wiring that you added.

The other possibility is that the circuit is properly grounded, and that the first box in the series (where you added the extension) was grounded via an external wire. Was this box a metallic box?

-Jon
 
  #8  
Old 10-31-04, 12:28 PM
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Oops, I didn't read the entire thread. Jon is correct, you may (or may not) have a terribly unsafe hazard. This must be further investigated, and corrected if necessary, ASAP before somebody gets killed. No ground at all is much, much safer than a bootleg ground. The reasons for this have been explained in millions of words in this forum.

However, the voltage readings you got are the same as in a correctly-wired system.
 
  #9  
Old 10-31-04, 01:10 PM
Daydrmr999
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the first box in the series is metal, how can i tell if it is grounded? Thanks

mike
 
  #10  
Old 10-31-04, 02:51 PM
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Use a neon circuit tester to see if it lights up when you touch the probes to the hot connection and the metal box. This isn't a fool-proof test, but it's better than nothing. If you find voltage there (and you probably will), then you are probably okay. Testing for true ground (not bootlegged) requires more sophisticated test equipment than you are probably interested in buying.
 
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