Very Old Underground Service

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OldSparks

Senior Member
Location
Vacaville CA USA
Occupation
Retired: Electrician, Submarine Electronics (21 years), Potable water system maintenance boss (21 years).
Doing some volunteer work on old buildings located on what used to be a military base in California. The underground feeders are just three conductors, the two phases and a neutral. No ground. I can mitigate hazards to humans by using GFCI's, but one subcontractor refused to connect his equipment to an ungrounded system. That got me to wondering just exactly how best to establish a ground. There is no ground buss in the main panel, just neutral. Thoughts?
 
In no particular order:

Is there metallic conduit and/or can an EGC be added?

Is there a parallel metallic pathway like water piping?

It's not ungrounded if the neutral can be bonded and used.
 
This is where the feed comes in. The main breaker is the Square D on the left. Lots of metal conduit and pipe in the ground. But where would a guy start to try to establish a ground buss in this mess? The large blue panel on the right has about a dozen breakers in it, but where and how best to establish a single point of ground escapes me.
 
OldSparks said:
. . . where and how best to establish a single point of ground escapes me.
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Inside the Square D main. The enclosure should be bonded to its neutral bus, and the conduits and enclosures downstream from there will be the EGCs.
 
Maybe I don't understand the question. An overhear service doesn't have an equipment ground pulled with it just 2 hots an a neutral. Why would underground change that?

You create the ground at the service. Ground rods, water pipe etc. connected to the neutral buss.
 
I am also confused. Is this a feeder or a service? If it's a service, three conductors is all you need. If it's a feeder to another building, it was compliant at the time to rebond the neutral at the detached building.
 
Okay guys, thanks. I was overthinking it and just didn’t want to do anything stupid.
 
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