Main panel at house. EGC from main panel to house ground rod.
Feeder (2 hots, neutral, ground) from main panel to garage panel.
Neutral and grounds isolated at garage panel.
EGC from garage panel to ground rod at garage.
Now ... what's your take on that arrangement?
i'm not going to address anything with code compliance, there are
folks here who can do that in their sleep.
the equipment grounding conductor is tying two separate grounds
together.
to my way of thinking, a service needs to be grounded to a SINGLE
reference point, to prevent differences of potential on the ground.
a floating ground, if you will.
that "single reference point" might be a ground grid made up of
10,000 feet of 500 mcm buried 2' in the rocks in a switch rack,
but for a service, not something in a POCO's backyard, a single
point of reference ground potential is desirable.
my experience with this was two ground rods driven in the floor
of an electronics test lab, a dozen feet apart, and a bare #6
running between them, along the back edge of a phenolic test
bench, for clipping equipment to, to eliminate ground loops.
i was 19 at the time, so i got to drive the ground rods. then
we bolted a #6 to one of them, ran it along the tabletop,
and went to bolt it to the other ground rod.
nothing hooked to the ground, not touching anything metal.
it drew a small spark. we measured the voltage between the
#6 and the unconnected ground rod... about 30 volts, fluctuating.
we got a simpson analog meter and checked again, figuring
transients being picked up by the lab grade VOM.
simpson wiggles between 20~30 VAC.
connected the wire to the second ground rod. nothing hooked
to that wire but those two rods, in the ground, 12' apart.
15~20 amps were flowing thru that #6, measured with an
analog clamp on. digital clamp on's didn't exist back then.
we never did find out why. disconnected the other ground rod
and checked the other way, same results.
that's why i'm a big fan of single point ground references,
unless the fault current available is so great that you need
a ground grid, like a switch rack.
one of things they taught in LADWP's safety class, if you had
a fault going to ground in a switchrack, don't stand with your
feet apart on the ground at the same time. you don't want
your job description to be "ground loop".
i figured if 230kv went to ground within 200 yards of me, the
chances of both of my feet touching the ground at the same
time until i was outta there wasn't real great.