VOLTAGE TO GROUND WITH THE NEUTRAL GROUNDED

Status
Not open for further replies.
bobby ocampo

bobby ocampo

Senior Member
LarryFine said:
A voltage from an open current pathway is very different from a voltage from capacitance.
Click to expand...
All system has a system capacitance. This is due to the potential difference from the line conductor to ground. Check chapter 1 of IEEE 142 or test by voltmeter yourself.
 
mtnelect

mtnelect

HVAC & Electrical Contractor
Location
Southern California
Occupation
Contractor, C10 & C20 - Semi Retired
Fred B said:
His hand contact is on the grounded side (neutral). If you follow illustration of the current flow, hand is onto the conductor after some sort of utilization device (maybe a light) on the side returning to the grounded point (possibly in the panel board), this is a current carrying conductor.
If the hand was simply on the grounding conductor your assertion would be valid, but illustration is not showing that.

Terminology specifics can get you.

Real life experience: My helper working on a switch and wiring replacement. Breaker of circuit off. Suddenly he got a shock. Got a measurement of 80V neutral to ground. Neutral was tied together with one on another circuit, and when someone in another room turned on the light the current took all available paths to source, including through my helpers hand .
Click to expand...

I am in the beginning stages of a NEC proposal based on your comments, see attachment.
 

Attachments

  • NATIONAL ELECTRIC CODE #1.pdf
    76.4 KB · Views: 11
bobby ocampo

bobby ocampo

Senior Member
Fred B said:
80 volts was a result of the splitting of the current between 3 circuit neutrals all tied together in a jbox. Additionally resistance of the equipment that the lighting circuit was turned on. And by metering between the neutral and grounding conductor at the switch that was being rewired it was measuring another conductor potential back to source. When the offending light was turned off no current present. Made a repair at attic jbox and no more shock and no more N/G voltage reading. Just continuity on N/G that would be expected on the home run.
Click to expand...
In an UNGROUNDED SYSTEM the system capacitance of a neutral to ground of a 240 volts line to line voltage is 70 volts more or less. Experiment with a voltmeter?
 
H

Hv&Lv

Senior Member
Location
-
Occupation
Engineer/Technician
bobby ocampo said:
Why do you think someone is complaining on washing machine shocking them? Is it because of no return path to the source that the circuit breaker won.t trip? Or was it because the ungrounded conductor is suddenly touching the non current carrying part of the equipment?
Click to expand...
Polarized plug backwards will do that.
 
don_resqcapt19

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
bobby ocampo said:
In an UNGROUNDED SYSTEM the system capacitance of a neutral to ground of a 240 volts line to line voltage is 70 volts more or less. Experiment with a voltmeter?
Click to expand...
You are talking about an ungrounded system in a reply to a post that is very clearly about a grounded system. Why?
 
tortuga

tortuga

Code Historian
Location
Oregon
Occupation
Electrical Design
Sea Nile said:
Work out the current and voltage assuming 25 Ohms of resistance for ground rod, 1000 ohms of resistance from hand to foot. And the conductor resistance of 14 AWG copper.

I would bet the current and voltage would be so insignificant that it wouldn't be a concern at all
Click to expand...
Well good point we need to put some numbers on this scenario say its a space heater in a barn.
First the load, say its 1440 Watts, that the max load you typically see on a 120V circuit, that would be a 10 ohm resistive load, like a space heater.
Now we need a circuit length; say its 490 feet out to the barn.
Now we'll use the numbers others have said, 25 ohms for the grounding system, and 1000 ohms across the person.
Now its just a matter of solving for the combination circuit.
EDIT Hold on never mind, he said the neutral, this is for the hot
voltage_drop.png
 
tortuga

tortuga

Code Historian
Location
Oregon
Occupation
Electrical Design
LarryFine said:
These threads seem like we're being interrogated. We have to keep answering the same questions until we get it right.
Click to expand...
Just think of it as a combination Series/Parallel Circuit refresher puzzle.
What do you come up with if they touch the neutral in the above scenario?
 
bobby ocampo

bobby ocampo

Senior Member
don_resqcapt19 said:
You are talking about an ungrounded system in a reply to a post that is very clearly about a grounded system. Why?
Click to expand...
Fred B said:
80 volts was a result of the splitting of the current between 3 circuit neutrals all tied together in a jbox. Additionally resistance of the equipment that the lighting circuit was turned on. And by metering between the neutral and grounding conductor at the switch that was being rewired it was measuring another conductor potential back to source. When the offending light was turned off no current present. Made a repair at attic jbox and no more shock and no more N/G voltage reading. Just continuity on N/G that would be expected on the home run.
Click to expand...
In an UNGROUNDED SYSTEM the system capacitance of a neutral to ground of a 240 volts line to line voltage is 70 volts more or less. Experiment with a voltmeter?

Mr Fred mentioned that he was able to get a voltage to ground of 80 volts. This will occur if the system is ungrounded measuring voltage from neutral to ground in an ungrounded system of 240 volts line to line. Try for yourself to verify
 
Last edited:
Status
Not open for further replies.
Top