HorneTD wrote in
nk.net:

B. Adams wrote:
HorneTD wrote in
ink.net:


B. Adams wrote:

Recently I had a breaker box installed in an outbuilding (Homeline,
70 amps max, with 2 20 amp breakers). Power is supplied via an
underground cable from the main fusebox in the basement of my house.
The distance is around 100 ft and the cable is 12-2 w/ground. I
wired the buidling myself (four circuits, 2 per breaker). The
circuits supply 1 light and 1 receptacle in one room and 1 light and
1 receptacle in the other. However, as there was no ground bar, I
tied all the grounds with the neutrals on the neutral bar. A
bonding screw was included but not used. My questions:

1. Does the NEC permit this? Is it safe? (I know that tieing
neutral and ground together on a subpanel in the same structure is a
no-no.)

2. Should the building have its own ground rod? There are no
connections between house and building except for the underground
feed.

No the US NEC does not permit that. Since there is an Equipment
Grounding (bonding) Conductor (EGC) in the cable you must use it to
ground all non current carrying parts of the electrical installation
back to the Service Equipment in the house. You need to install an
add on EGC buss bar in the Garage's panel. These are available
wherever SquareD equipment is sold. You then put all the EGCs on the
add on buss bar and keep all of the neutrals on the built in buss
bar.
The reason for not running the neutrals and EGCs on the same buss
bar
is that in the event of an open neutral between the garage and the
utility's transformer the voltage on all exposed metallic parts of
the garage's electric system will go dangerously high if the EGCs are
not separate from the neutrals.

The separate building does need it's own grounding electrode system.
The minimum is a driven rod, eight feet or more in length, which
measures less than 25 ohms resistance to earth after installation.
The code requires that a second rod be added unless the first
measures than 25 ohms. Once you install a second rod the code is
satisfied so most electricians install two rods to be done with it.
The two rods must be at least six feet apart but more is better.
Best practice would be to have driven the two rods through the bottom
of the wire trench at ten and twenty feet from the building
respectively and connect them back to the panel with bare number 2
AWG run in the bottom of the trench. Since it sounds like the trench
is long back filled it is too late for that. Just drive the two rods
at least six feet apart and connect them back to the garage panel
with bare number four copper wire. Using an acorn clamp on each rod
run the wire from the furthest rod back to the nearest rod through
it's acorn clamp and back to the add on buss bar in the garage panel.
That bare copper wire is called the Grounding Electrode Conductor
(GEC). It must be protected by conduit if it is exposed to severe
physical damage such as from lawn mowers or power trimmers.
--
Tom Horne


As I wrote in my original post, a bonding screw came with the breaker
box but was not used. The instructions read: "When it is required to
bond box to neutral plate, use long screw enclosed. Insert through
hole in neutral plate and thread into hole in box." Does the NEC
require it, in addition to adding a ground buss?
No the US NEC Does not require or permit the installation of the
bonding screw in this case. To install it would be a violation of
250.24 (A) (5) vis..
250.24 Grounding Service-Supplied Alternating-Current Systems.
(A) System Grounding Connections. A premises wiring system supplied by
a grounded ac service shall have a grounding electrode conductor
connected to the grounded service conductor, at each service, in
accordance with 250.24(A)(1) through (A)(5).
(5) Load-Side Grounding Connections. A grounding connection shall not
be made to any grounded circuit conductor on the load side of the
service disconnecting means except as otherwise permitted in this
article. --
Tom Horne

UF was indeed used and GFCI receptacles.