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manforthejob · Jan 19, 2009, 12:28 PM

While replacing burnt outlet from portable heater (I didn't do it!) got 8 volt reading between ground and nuetral could device elswher on circuit be causing this ?

stanfortyman · Jan 19, 2009, 01:08 PM

8 volts with a digital meter is likely nothing more than phantom voltage. I would not worry about it. The breaker was off and you tested the wires to a known ground, right??

andrewc24301 · Jan 19, 2009, 06:57 PM

Originally Posted by stanfortyman

8 volts with a digital meter is likely nothing more than phantom voltage. I would not worry about it. The breaker was off and you tested the wires to a known ground, right?????

Stan Forty:

I'm curious (as I do not know the codes through and through as you all do), but if the neutural is bonded to the ground in the service panel, then shouldn't any low voltage present on either the ground or neutral zero out due to being on the same potential?

KISS · Jan 19, 2009, 07:49 PM

I disagree. I think 8 volts is too high.

Makes me think that you lost ground somewhere.

stanfortyman · Jan 19, 2009, 08:49 PM

Originally Posted by andrewc24301

Stan Forty:

I'm curious (as I do not know the codes through and through as you all do), but if the neutural is bonded to the ground in the service panel, then shouldn't any low voltage present on either the ground or neutral zero out due to being on the same potential?

No, because the neutral is isolated from the grounds all the way back to the panel.

Google "phantom voltage" and you will get a ton of info on it.
Here is the Wiki page (although I acknowledge Wiki is not always right): Phantom voltage - Wikipedia, the free encyclopedia

Handyman2007 · Jan 22, 2009, 07:07 AM

Originally Posted by KeepItSimpleStupid

I disagree. I think 8 volts is too high.

Makes me think that you lost ground somewhere.

I agree 100%. There should be little or no voltage present between ground and neutral. There is something wrong here. Any "stray" would be 1 volt or less. Check back to the service box. If in doubt , call an electrician.

stanfortyman · Jan 22, 2009, 04:11 PM

Originally Posted by Handyman2007

I agree 100%. There should be little or no voltage present between ground and neutral. There is something wrong here. Any "stray" would be 1 volt or less.

Really? Do you own a good digital meter? Youv'e never read 5-10 volts or more where NONE existed?

Are you familiar with the term "phantom voltage"?? It is a REAL issue, and is not something I just thought up.

Handyman2007 · Jan 22, 2009, 04:32 PM

Try putting an ammeter between neutral and earth ground... that is a more important factor. If there is stray current. Then, I must insist, there IS a problem.
And to answer your question, never on one of my installations,, ever.

stanfortyman · Jan 22, 2009, 04:48 PM

Originally Posted by Handyman2007

If there is stray current. Then, I must insist, there IS a problem.

Stray current is NOT phantom voltage. Not even close.

Originally Posted by Handyman2007

never on one of my installations,,,,ever.

Gee, me neither. But I have seen it in many existing settings where absolutely NO problem existed.
I suggest you look it up. It is not a new thing.

pelle · Jan 22, 2009, 05:27 PM

There should be no voltage on a neutral wire.. Stan you are correct about phantom voltage if you are using a non true rms meter I have seen 5-8 volt differences with the inexpensive meters. That being said voltage on the neutral could come from a lot of different things i.e.. A TV plugged into a non polarized outlet backwards.. (ask any cable installer about this one)..
"Man" try this turn the main breaker off in the house and check the neutral to ground reading. If it drops to '0' then the problem is inside . Turn main breaker back on and one by one check each individual breaker on to off to see when the voltage goes away. When it does go away that is the problem circuit. If when turning off the main breaker the voltage does not go away call your electric utility they should be able to isloate the problem.

Stratmando · Jan 22, 2009, 05:31 PM

I would check for voltage between the Neutral and Ground at the Panel.
I thought Phantom was power being supplied to a circuit, even though it is off, a TV needs the Ir receiver to have power, so it can turn it on, draws power when the TV is off.

KISS · Jan 22, 2009, 05:51 PM

I know how those voltages get generated and they are real, but are not supposed to be there.

The one place they are not usually not from is the input bias current of the meter. The 10 M input Z swamps it out.

Ground loops are not phantom voltages.

One that might be considered a phantom voltage is when a ground opens and a device with a 3 prong plug and an RFI filter dumps to what it thinks is ground. The leakages there can be an AC impeadance or a DC resistance and can act as a voltage divider.

pelle · Jan 22, 2009, 06:01 PM

Kiss can phantom voltage be equated to capacitance. We get that a lot on long runs of underground cable where you will get voltage readings to ground but you can bleed it off with a light bulb on a pigtail and get the reading to '0'.. obviously the light bulb won't light which is how we know it is capacitance and not real voltage.

Stratmando · Jan 23, 2009, 05:48 AM

pelle, that is voltage, however, it has no amps to do anything with, my belief.