You may add any supplemental grounding your heart desires. The rule is
that the grounded conductor may only be grounded at one location. The
grounded conductor is often mislabeled as the neutral, but it is always the
"white" wire and is bonded to ground at the service entrance. This is the
only location that it is allowed to be bonded. (your meter)
As long as you do not connect the "neutral" (grounded conductor) with the
grounding conductor, in this location, any new grounding is okay.
However, lightning protection is generally anecdotal. Essentially, you can't
win if it wants you to lose.
As Tom wrote, there should have been a grounding electrode in the
As RBM wrote, the practice with a 3 wire feeder was to bond the neutral
and ground at the garage. As greg wrote, starting the 2008 NEC 3 wire
feeders are not allowed for new wiring.
A lightning strike to the garage requires lightning rods for protection.
A lightning strike coming from the house (from the service wires) on the
feeder may result in the feeder wires at very different potential than
the earth at the garage. Ground rods wouldn't help equalize the
potential much. Bonding to the mesh/rebar in the floor at installation
time would be nice. A suppressor at the feeder panel in the garage
would help protect equipment in the garage.
It is not allowed, and for some time, to re-bond the grounded conductor
unless a "new" service is established. At no time is it allowed for the
grounding conductor to carry current. Period, end of damned story.
Correct. The electrical grounding of the system is its "own" system.
Lightning protection is a separate system with strange results.
Three electricians and an inspector have said the neutral of a 3 wire
feeder to a garage would, until the 2008 NEC, be bonded to the system
ground and earthing electrode in the garage.
In the current NEC, quoted in another post, this practice is explicitly
Period, end of damned story.
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