Diode on ground?

Caspion

Member
Location
Socal
Occupation
Electrician
So I'm doing a service upgrade for my Brother on a home he just bought in Southern California and along with a multitude of code violations I also found that there is what looks to be a large diode attached to the incoming "neutral " prior to the conductor lug on the power companies side
it's old and just solid black with no visible text or embossing has anyone come across this before? And the only thing I can think of is that there was some type of current present because the ground was undersized and poorly bonded to the cold water line about 20 feet into the attic. Just want to know If i should be worried about not putting it back so long as I install a 5/8 ground rod
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
I doubt it has anything to do with grounding at all. It might be an old lightning arrestor.

If it is within the power company wiring I don't see how you can take it out. It belongs to them.
 

Caspion

Member
Location
Socal
Occupation
Electrician
I doubt it has anything to do with grounding at all. It might be an old lightning arrestor.

If it is within the power company wiring I don't see how you can take it out. It belongs to them.
Well it's on their side of the panel but the feeders to the pull box is homeowners responsibility then from the pull box located in the driveway it goes to the vault so they have a 5 hex on the pull box they just come and disconnect at the vault and pull the meter any necessary upgrades to wire size from there is homeowners responsibility and then they would access their side from vault to pull box
 

Caspion

Member
Location
Socal
Occupation
Electrician
I doubt it has anything to do with grounding at all. It might be an old lightning arrestor.

If it is within the power company wiring I don't see how you can take it out. It belongs to them.
It's also hooked linear on the ground only
 

Josh111

Senior Member
Location
USA
Wouldn't make sense for a diode to be used on an AC circuit. I too think that if it's in the meter, you should be consulting with the power company. Having seen no photos hard to know, but maybe it's some kind of power factor correction component? Or maybe radio interference mitigation?
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
My gut instinct is that it is a neutral isolator to deal with a high neutral to ground offset in the utility MGN. Something like back to back Zener diodes which only conduct under fault conditions when the applied voltage exceeds about 10 volts.
Under normal conditions any local neutral current is carried through the ground electrode path instead.
If there is indeed a problem on the utility side, leaving it out will result in high neutral current into the building GES even when there is no load at all. The result will be a significant offset between EGC and "real" local ground on objects with earth contact, like drain pipes, etc.
This voltage offset would probably not be dangerous, but could be irritating.
For a dairy operation it could be intolerable.
Normally a POCO-supplied ground isolator would be installed in a labelled enclosure though.

If you test it, expect to read an open (or very high resistance) circuit unless you apply a high enough test voltage.
 
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