Brandon Loyd
Senior Member
Should I be concerned if I find neutral to ground voltages (0.855v) present on random electrical equipment?
Neutral to ground voltage
- Thread starter Brandon Loyd
- Start date
- Status
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
I would not be concerned and in fact that is normal to have some voltage.
Brandon Loyd
Senior Member
At what point should I be concerned? Over 3 volts? Would you agree this could be cause by harmonics issues or bonding issues?
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
111130-1506 EST
Brandon Loyd:
Just made some measurements. Readings change from time to time and where measured.
Ground at the main panel to ground on my workbench, 0.027 V and fairly stable.
Bench ground to neutral at same outlet 1.05 V, then changed to 0.087 V.
Bench ground to neutral at same outlet 0.106 changes to 1.254 V with 1160 heater plugged into same outlet.
Same outlet hot to neutral with no load 125.3 V drops to 121.1 V with 1160 W load.
1160 W at 121.1 V is 9.579 A. Total loop drop was 4.2 V at 9.579 A. But on neutral to the main panel about 1.1 V or 3.1 V for hot side from pole transformer to bench outlet and neutral from pole to main panel.
Get two plastic handle 10 or 12 inch screwdrivers. Two meter leads with clips each about 6 ft long. Connect the meter leads to the meter and screwdrivers. Pick different spots in your backyard and insert the screwdrivers in the ground about 12 ft apart. Measure the AC voltage. Change the angle of the line between the screwdrivers at the same location and read the meter. You pick angles like 0 (meaning N-S), 45 deg, 90 deg (E-W), and 135 deg. Pick another spot and do the same. Does the angle of maximum voltage remain the same or change?
.
Brandon Loyd:
Just made some measurements. Readings change from time to time and where measured.
Ground at the main panel to ground on my workbench, 0.027 V and fairly stable.
Bench ground to neutral at same outlet 1.05 V, then changed to 0.087 V.
Bench ground to neutral at same outlet 0.106 changes to 1.254 V with 1160 heater plugged into same outlet.
Same outlet hot to neutral with no load 125.3 V drops to 121.1 V with 1160 W load.
1160 W at 121.1 V is 9.579 A. Total loop drop was 4.2 V at 9.579 A. But on neutral to the main panel about 1.1 V or 3.1 V for hot side from pole transformer to bench outlet and neutral from pole to main panel.
Get two plastic handle 10 or 12 inch screwdrivers. Two meter leads with clips each about 6 ft long. Connect the meter leads to the meter and screwdrivers. Pick different spots in your backyard and insert the screwdrivers in the ground about 12 ft apart. Measure the AC voltage. Change the angle of the line between the screwdrivers at the same location and read the meter. You pick angles like 0 (meaning N-S), 45 deg, 90 deg (E-W), and 135 deg. Pick another spot and do the same. Does the angle of maximum voltage remain the same or change?
.
SG-1
Senior Member
- Location
- Ware Shoals, South Carolina
Here is an article by Fluke that covers you question.
http://support.fluke.com/find-sales/Download/Asset/1989076_6116_ENG_D_W.PDF
http://support.fluke.com/find-sales/Download/Asset/1989076_6116_ENG_D_W.PDF
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
if there is any current flow on your neutral, you will have voltage drop. since there is no current flow on the ground wire (or at least there should be none), there will be no voltage drop there, so there will be some differerence in the potential between N-G the farther you get from the N-G bond when there is current flow.
brian john
Senior Member
- Location
- Leesburg, VA
I have posted this before, but I had a job with 120 VAC between neutral and ground. This was a 3 phase 4 wire, 45 KVA motor generator. The XO/Neutral was never grounded, at some point there was a short from a 20 amp ?A? phase circuit breaker to ground.
Readings were
At the MG distribution panel.
?A? - Neutral 120 VAC, ?B? - Neutral 120 VAC, ?C? - Neutral 120 VAC,
?A? - Ground 0 VAC, ?B? - Ground 208 VAC, ?C? - Ground 208 VAC, Neutral - Ground 120 VAC.
This was a skiff (SP) full of top secret, very sensitive electronic equipment with iron clad construction specs (that no one verified compliance to), this site had been there at least 10 years and no reported equipment failures. The issue was discovered when new equipment was being installed.
The biggest issue with high neutral to ground voltage in a PROPERLY installed distribution system is high voltage drop on the branch circuits.
Readings were
At the MG distribution panel.
?A? - Neutral 120 VAC, ?B? - Neutral 120 VAC, ?C? - Neutral 120 VAC,
?A? - Ground 0 VAC, ?B? - Ground 208 VAC, ?C? - Ground 208 VAC, Neutral - Ground 120 VAC.
This was a skiff (SP) full of top secret, very sensitive electronic equipment with iron clad construction specs (that no one verified compliance to), this site had been there at least 10 years and no reported equipment failures. The issue was discovered when new equipment was being installed.
The biggest issue with high neutral to ground voltage in a PROPERLY installed distribution system is high voltage drop on the branch circuits.
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