so i was working in an old home today, where the second floor plugs and lights are ran all on the same circuit, there was a mix of new and old wiring already in the walls, i simply had to attach some grounds to the plugs because some dummy decided to not use them. anywho, another item on my punch list was a light that the homeowner wanted changed into a ceiling fan, so in the process of swapping the fixture i forgot what wires where what...switch leg, and hot, the light was fed before the switch. as i was doing so i tested one wire to neutral which was the hot which gave me 120v..i tested the other wire (which was the switchleg) and it gave me 60volts to the neutral, the switch was off though, when i turned it on it gave me 120v. when the whole cb was turned off the 60 volts went away also. upon more testing i found that all the plugs have 60 volts to ground but at the panel there is 120 to ground. does this mean somewhere along the line i have a bad ground?? is the neutral and ground tied together possible somewhere seeing as how i got 60 volts on the neutral as well at the light? by the way i got 120 to neutral at all of the plugs. any info would be greatly appreciated. i walked around in a lot of circles today trying to narrow it down
bad ground??
- Thread starter Dg01501
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SG-1
Senior Member
- Location
- Ware Shoals, South Carolina
If you are using a high impedance Digital Multi Meter then the readings are most likely false. You need a wiggy or a meter with a Low-Z setting.
What you were measuring is caused by capactive coupling. If a load is applied the reading becomes normal.
What you were measuring is caused by capactive coupling. If a load is applied the reading becomes normal.
kwired
Electron manager
- Location
- NE Nebraska
You very well may have different readings with a high vs low impedance voltmeter.
Couple other things: sounds like the neutral is possibly switched on the light, and there is open circuit someplace on the equipment ground on the receptacles. No matter which meter you have you should get good voltage from hot to neutral or ground if the conductors are good, so something is open somewhere or has a high resistance.
Couple other things: sounds like the neutral is possibly switched on the light, and there is open circuit someplace on the equipment ground on the receptacles. No matter which meter you have you should get good voltage from hot to neutral or ground if the conductors are good, so something is open somewhere or has a high resistance.
- Location
- Tennessee NEC:2017
- Occupation
- Semi-Retired Electrician
I'm confused, at one point you said you had 60V at the plugs, and then you said you had 120V at the plugs. But it sounds like you might have a set up where the neutral was the switched hot and bonded to the outlet. I might have not described that well, but in some older wiring there was a dangerous set up where the neutral was hot at the lights. Then again, if you have low voltage everywhere upstairs, you probably have an open neutral somewhere.
Rick Christopherson
Senior Member
This is expected. When the switch is open, that conductor is floating, and you will have an induced voltage from adjacent conductors.
The first thing I noticed in your posting was the comment that the previous electrician didn't bother to connect the grounds at receptacles. My immediate thought was that he didn't do this (right or wrong) because the ground didn't really exist. This is supported by your measurement of voltage from neutral to ground at the receptacles. You have an open ground.
Sorry for the nit-pick, but the voltage is not false. It is just more accurate than you/most would prefer. The voltage is real, but the analog meter just masks it.
ptonsparky
Tom
- Occupation
- EC - retired
Older homes you will quite often find that the neutral is switched. Just a fact of life. Same with no EG, someone extended the existing circuit and had no place to hook it to anyway. Both stated already.
Run a good three wire extension cord all the way down to the SE and plug it into a receptacle you know is wired correctly, even if you have to install one. Use this as a testing reference pont to find your hots & neutrals.
Don't trust your pen tester for much of anything.
Run a good three wire extension cord all the way down to the SE and plug it into a receptacle you know is wired correctly, even if you have to install one. Use this as a testing reference pont to find your hots & neutrals.
Don't trust your pen tester for much of anything.
SG-1
Senior Member
- Location
- Ware Shoals, South Carolina
Perhaps this will help to better explain my position, Mr. Christopherson.
View attachment Bulletin-88 Phantom Voltage.pdf
Fluke makes a meter attachment to deal with this. It is a SV225.
View attachment Bulletin-88 Phantom Voltage.pdf
Fluke makes a meter attachment to deal with this. It is a SV225.
Attachments
- Location
- Tennessee NEC:2017
- Occupation
- Semi-Retired Electrician
Fine line between common practice and done a lot, but yes, it used to be done.
kwired
Electron manager
- Location
- NE Nebraska
If it is a capacitively coupled voltage that is being measured, it seemingly disappears with a low impedance meter because the impedance of the meter is low enough to cause the connection through the meter to essentially short out the 'capacitor' which is a very weak 'capacitor' in the first place. This 'capacitor' is nothing more than two or more circuit conductors separated by their own insulation.
kwired
Electron manager
- Location
- NE Nebraska
Non contact testers use capacitive coupling to make them show a voltage is present. I would not trust the reading of one of those to determine what is going on. If you don't have a low impedance meter all you need to do is apply a load to the circuit being tested, just about any resistive load you can imagine will work, light bulb of any wattage will do. A capacitively coupled circuit will not be able to sustain enough voltage to supply the load and you will have essentially no voltage reading at all if the only voltage source is from capacitive coupling.
Rick Christopherson
Senior Member
No need to be snide. I know what a phantom voltage is, but you said it was a "False" reading, and that is the part that is not correct. That is what I was pointing out. The voltage is real, but a low impedance meter dissipates (masks) that voltage. In most power situations it can be ignored, but in some control situations, it cannot. Furthermore, this is important to understand because it may help during various troubleshooting situations, where you have a floating conductor, but wouldn't necessarily realize it if the stray voltage was always masked.
SG-1
Senior Member
- Location
- Ware Shoals, South Carolina
By "false" I mean the voltage measured cannot begin to power a load, but can lead troubleshooting astray. If the situation at hand were a printed circuit board, or other sensitive devices we would be in complete agreement.
mbednarik
Member
- Location
- central iowa
- Occupation
- Electrician
is this an illuminated switch, these actually use the light to complete a circuit. so the light in the switch is in series with the light on the ceiling, and when turned on the light in the switch is shunted, turning on the light on the ceiling. at least that is how to p and s illuminated switches work.
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