Is the building merely metal skinned or does it have a metal frame as
well? What is the foundation for the building and is it steel
reinforced with reinforcing bars? Were is the building located? I
don't want the street address but I need the state in order to gage the
Under the US NEC the metal frame of the building must be bonded to the
grounded current carrying conductor of the electrical service that most
of us call the neutral. If the building has a metal frame that is
bolted to a concrete foundation it may be grounded already by the
reinforcing steel in the footing. If the footer does not contain any
rebar and the frame is therefore not effectively grounded then a three
foot trench should be dug around the entire periphery of the building to
permit installation of a ground ring. A ground ring is a number two
American Wire Gage or larger conductor that is buried around a building
at a depth of at least thirty inches. Best practice is to bury it below
the permanent moisture level. From the ground ring a Grounding
Electrode Conductor would be run to the service disconnecting means
enclosure as well as to each major column of the frame of the building.
If the permanent moisture level is well below the surface of the earth
then sectional ground rods should be driven at each corner of the
building to below the permanent moisture level if the building is in a
lightning prone area. These rods would then be bonded to the ground ring.
I live in South Louisiana and the building is metal framed and skinned with
the frames being bolted to anchor bolts that were placed in the concrete
slab. Rebar was used in the footer perimeter. (Would the anchor bolts need
to be touching the rebar to be considered grounded as per your explanation
If I satisfy the grounding requirements, does that mean that I will still
need to "bond" the building to the ground rod ?? Could you explain how to
bond to the frames ??
I don't know how fancy you want to get. I built a couple of
buildings for a major gas pumping outfit here. They required the
full ground ring around the perimeter buried 4' minimum with a
grounding stinger cad welded to the building ring and to each
column. Cad welding is explained here:
but is basically a molten metal connection that uses powdered
copper oxide and aluminum that is ignited. Your electrician
should be familiar with the system.
These things can be accomplished with mechanical fasteners.
(top posted for your convenience)
Keep the whole world singing . . . .
DanG (remove the sevens)
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