Attempting to connect two #14 ground wires to a single ground screw in
single-tube Lithonia fluoresecent fixtures joined end-to-end resulted in
stripping the screw threads in the sheet steel fixture. Is it acceptable to
substitute the next larger size of self-tapping machine screw. Of course it
won't be green and will be cadmium or zinc plated.
Alternatively, a longer ground might be screwed through a nut on the
backside of the fixture but this would be inconvenient.
Maybe. No requirement for it to green. There is a prohibition on the
use of sheet metal screws for grounding and bonding. There is also a
variety of opinions on whether a self tapping screw is the same as a
sheet metal screw. The way the code is written it could be
interpreted that any screw other then a "sheet metal screw" would be
acceptable (i.e. drywall screw, wood screw, etc.) I am not sure that
was the intent.
250.8 Termination of Grounding and Bonding Conductors
Equipment grounding conductors, grounding electrode conductors, and
bonding jumpers must be terminated by exothermic welding, listed
pressure connectors (set screw, compression), listed clamps, or other
listed fitting. Sheet-metal screws shall not be used for the
termination of grounding conductors.
Note: If a screw is used for grounding that screw shall not be used
for any other purpose.
Next size up is acceptable. It doesn't have to be green.
However -- the unacceptable part here is trying to put two wires under one
screw. Code prohibits connecting multiple wires to a single terminal unless
the terminal is specifically approved for multiple wires -- and you just
discovered one of the reasons why.
So for this one, and to avoid similar problems on other fixtures in the
future, loop a short (6" or so) pigtail around the grounding screw, and
wire-nut it to the two #14 ground wires.
Doug Miller (alphageek at milmac dot com)
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