I was cleaning up the wiring around the electrical panel in an older house that I've bought and got a small shock from a circuit ground wire that was not connected to the panel (the hot and neutral were connected). I checked with a multimeter and have found that I have 50 volts on the ground when tested against the neutral and 120 when tested against the hot. Some other grounds are showing 10-30 volts. I don't think this is normal. Is it normal and if not, is it possible that there is a short that is energizing the neutral bar? What would be the best way to isolate the problem?

KeepItSimpleStupid

If you were moving the grounds with the circuits on, 50V is not uncommon. Switching power supplies dump their RF energy to ground even when things like TV's are off.

Disconnecting grounds like you did has the possibility of letting the magic smoke out of electronic devices. e.g a USB printer and a computer where one of the devices was grounded properly and the other ground was lifted.

stanfortyman

Was the neutral bond screw/strap in place in this panel? I assume it was the main panel....

weasel7023

It is the main panel Stan. As for the screw, I'm not sure which screw you mean. It's a GE panel (it appears fairly new) with a ground bar on one side and a neutral on the other. The two are bonded via a strap, but the small screw bonding the neutral/ground bars to the main panel box is still in the bag sitting on the bottom of the panel. There are neutral and ground wres attatched to the same bus bars on both sides with the neutral and main ground (ground running to the earth) all connected together at the main neutral lug. I would think that the neutrals are supposed to be on the neutral bar which is connected to the neutral lug and the grounds on the ground bar connected to the ground lug which would then go to earth. I would think that's the way it should be but I could be wrong......


Thanks for your reply keepitsimple. I do have about 7 electronic items on the circuit with 50 volts coming back down the ground.

KeepItSimpleStupid

This is the place where neutral and ground have the same potential and where neutrals and grounds are connected together (ground rod, neutral lug, neutral, ground). Usually it's a cost cutting measure on the part of the panel manufacturer to not have an extra ground bar.

A ground bar is sometimes an accessory for sub panel wiring. Sub-panels MUST keep the neutrals and grounds isolated. They are connected together in the main panel.

The 50 V feedback is normal. Your best killing power to the entire panel before making changes live.

KeepItSimpleStupid

Here is an example of a filter for florescent lights. FL Series

Note, that in this case, there is a capacitor to ground. Capacitors are not ideal and have a leakage current, thus if the ground is lifted the, leakage current divides the line voltage almost in half because the capacitors are nearly identical.

The meter used to measure it may also divide the measured voltage.

This is the 50V your seeing at the panel. Switching power supplies, dimmers all have line filters built in. Electronics that are "off" may draw 4 W or so.

Stratmando

Determine what is on that circuit, then hook meter on neutral and ground to see the 50 volts, then unplug anthing on that circuit, turn off any lights, fans, etc til voltage is gone to determine the leak to ground, turn on lights, plug in TV or whatever, each time noting voltage did not appear.
Neutral and ground should be tied together at service or panel and should be closer to zero volts between neutral and ground.

KeepItSimpleStupid

Strat:

You were not paying attention. It appears that the OP was lifting the ground at the main panel with the power on and measuring the resultant voltage from the lifted wire and panel ground. 50-60 VAC is likely and there is nothing wrong.

Stratmando

KISS, I understood well, With the ground lifted and loads removed that would leak to ground would show as a voltage.
If I lift a ground at MY panel, and see voltage, something is leaking to ground. If I remove the culprit, the voltage will be gone.