Voltage on neutral wire of outlet

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  #1  
Old 05-14-04, 09:45 AM
FrankM1
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Voltage on neutral wire of outlet

Going from line to load I have 124V, but I also have 36 volts if I go from the neutral to ground. The connections are good in the fuse box, and I pulled the outlet covers off the other outlets in the circuit, everything seems to be wired correctly. I found it using a non-contact voltage probe. Any ideas what could cause this?
Thank You
Frank
 
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  #2  
Old 05-14-04, 09:50 AM
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The key question is, if you plug a lamp into that receptacle, does it work?

You may have either an open ground or an open neutral.
 
  #3  
Old 05-14-04, 10:30 AM
FrankM1
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The outlet works fine.
 
  #4  
Old 05-14-04, 11:06 AM
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When you say 'you found it with a non-contact voltage probe', did you actually measure this ground to neutral voltage with a two probe volt meter?

Were you measuring this voltage between the ground and neutral terminals on a receptacle, or between neutral and some convenient 'ground'?

Do you have a good solid connection between the volt meter probes and the points you are measuring?

Have you tried killing power to the circuit and measuring the _resistance_ between the ground and neutral?

Do you have single phase power (normal home) or three phase power (many industrial supplies, as well as some large apartments)?

-Jon
 
  #5  
Old 05-14-04, 11:34 AM
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I'd say you have no grounding. Is there some reason that you think you should have grounding? In what year was the house built?

I just kinda ignored that part about measuring a voltage difference with a non-contact probe. That didn't actually make sense to me.
 
  #6  
Old 05-14-04, 11:42 AM
FrankM1
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Jon
After I found voltage at the neutral with the circuit tester I tested it for voltage with my multi-meter. I mispoke above: if I go from the neutral wire/terminal/or outlet socket to the bare ground or gang box I get 24 volts, if I check from load to bare ground or gang box I get 48 volts.

I think my readings were good/solid, I've checked it at least a dozen times with the same results. I tracked the wire down in the fuse box, it's a GFI breaker, I pulled the breaker and checked terminations and they were tight. Connections to the ground bar in the box are good also.

Single phase

I will try checking resistance tonight.

Thank You
 
  #7  
Old 05-14-04, 12:23 PM
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Frank,

Please answer the question about the ground. Do you KNOW that a ground wires exists from the panel to the receptacle? Do you KNOW that the box is properly grounded.

I suspect that thjis particular receptacle, and perhaps much of your house, is not grounded.

Answer John's questions, about when the house was built, etc.
 
  #8  
Old 05-14-04, 12:46 PM
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In fact, your voltage readings are not good. You are being fooled by phantom voltage. Put away your voltmeter for a while. It is leading you astray. Answer the questions we have asked.
 
  #9  
Old 05-14-04, 12:53 PM
FrankM1
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The house was built in 1979, the entire house is grounded. This is the only outlet in the entire house that has this problem, I checked every one with the circuit tester. The bare ground in the gang box is wrapped around the bolt that holds the wires in place in the box and tightened down then continues on to hook to the green grounding screw on the outlet itself. This is the last box in the run so it only has the one 3 wire cable coming in.

Just within the last 3 months I also had the power company check the trasnformer ground and the ground in my fuse box to make sure they were operating properly.
 
  #10  
Old 05-14-04, 01:00 PM
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So if this is the last box in the run, then check the grounding connections in the second-to-last box in the run.
 
  #11  
Old 05-14-04, 02:04 PM
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Actually, you have answered the necessary questions. The outlet clearly has a bad ground, or your meter's connection to the ground pin is bad.

The fact that a light works fine means that you have 120V hot to neutral.

The fact that your hot to ground and neutral to ground voltaged don't add up to 120V means that you have an _open_ ground. The wires may be in place, but somethine is broken somewhere.

As John said,your multimeter is reading 'phantom voltage', capacitively coupled voltage on a non-connected line. A very useful test instrument for this sort of stuff is a _low_ impedance volt meter, such as a 'wiggy'. These will 'short out' the phantom voltage, and give you a true reading of the supply voltage applied to a line.

Note that enough current will flow though a wiggy to trip a GFCI breaker.

Somewhere between this receptacle and the previous one in the chain, the ground is broken. It may look correct, but the receptacle is not grounded.

-Jon
 
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