Proper Metal Box Grounding For Lighting Fixtures?

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JFletcher

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Williamsburg, VA
It's been a long while since I've been here... anyway, we (my area) is on the 2011 NEC... I only have the 2008 version. That aside, my question:

How do you properly ground a metal light fixture?

Scenario: metal (cast aluminum kind, 5 KOs) box, for lights, is fed by premise wiring (NM). Is it okay to ground premise wiring to ground screw provided in the box, then ground the light to the tie-bar ground screw, w/o the two being tied together? Are the screws/tie bar/box a sufficient ground path, or do the grounds of the light and the premise wiring need to be tied together, either by crimp or wire nut, to each other, after being wrapped around the ground screws?
 
I have seen that type of install before. Never liked it.

Whether legal or not, I have not really ever nailed it down. I want to say no, but.....

This is the code section:

410.44 Methods of Grounding
Luminaires and equipment shall be mechanically connected
to an equipment grounding conductor as specified in
250.118 and sized in accordance with 250.122.
 
ty for the reply, Derek. I have looked over the code sections you cited in the 08 NEC, 410.44 is 410.46. I did some digging, and 250.148(B) seems to stick out to me:

"Grounding Continuity: The arrangement of grounding connections shall be such that the disconnection or the removal of a receptacle, luminaire, or other device fed from the box does not interfere with or interrupt the grounding continuity"

So, if the grounds arent tied together (other than by the box), removing the luminaire and the tie bar would break continuity of grounds. Am I interpreting this correctly? It is possible to remove the luminaire w/o removing its tie bar.

Dont know if it matters, but none of these lights are in a location where they can be accidentally touched, so would 410.42(A): '...inaccessible to unqualified personnel..." have any bearing here?

In any event, I will be tying light ground to premise ground and to the box and tie bar (unless this is incorrect).
 
JFletcher said:
ty for the reply, Derek. I have looked over the code sections you cited in the 08 NEC, 410.44 is 410.46. I did some digging, and 250.148(B) seems to stick out to me:

"Grounding Continuity: The arrangement of grounding connections shall be such that the disconnection or the removal of a receptacle, luminaire, or other device fed from the box does not interfere with or interrupt the grounding continuity"

So, if the grounds arent tied together (other than by the box), removing the luminaire and the tie bar would break continuity of grounds. Am I interpreting this correctly? It is possible to remove the luminaire w/o removing its tie bar.

Dont know if it matters, but none of these lights are in a location where they can be accidentally touched, so would 410.42(A): '...inaccessible to unqualified personnel..." have any bearing here?

In any event, I will be tying light ground to premise ground and to the box and tie bar (unless this is incorrect).
Click to expand...

250.148(B) is referring to the continuity of the EGC for downstream connections, so yes tie all EGCs together and then connect to fixture, box, etc.

I got a bit lost on your description. Here is how I do it:

Wire nut all EGCs together with 2 extra pig tails.

Use 1 tail to bond box.
Use other pig tail for bonding strap and connect to fixture, a little loop on the strap.

Everything is bonded and replacing fixture is easy.

Forget "410.42(A): '...inaccessible to unqualified personnel", that just gets things confusing. Keep it simple is my advice.
 
The question is can two EGC's be connected together by the metal box. I say yes, there is a prohibition for grounded conductors but not grounding conductors.
 
jumper said:
250.148(B) is referring to the continuity of the EGC for downstream connections, so yes tie all EGCs together and then connect to fixture, box, etc.

I got a bit lost on your description. Here is how I do it:

Wire nut all EGCs together with 2 extra pig tails.

Use 1 tail to bond box.
Use other pig tail for bonding strap and connect to fixture, a little loop on the strap.

Everything is bonded and replacing fixture is easy..
Click to expand...

I pretty much do the same: With a ceiling box, first I make sure that all conductors are at least twice the length of the width of the box.
I then will fold/ben and lay approx 3" or so of the egcs against the side or bottom of the box. Of the excess that is left over, I will pretwist approx 2" of the egcs and place a (buchanan) crimp in the middle of that twist and will use any tails protruding from the end of the crimp as needed-1 to bond the box and 1 to bond strap/fixture etc.

I like to do this even with recs and sw's too. Many will say its unnecessary to tail the egc out to a rec/sw thats already secured to a bonded metal box, but its just my way of ensuring that those devices are grounded no matter what-redundancy is good when it comes to egcs.
 
infinity said:
The question is can two EGC's be connected together by the metal box. I say yes, there is a prohibition for grounded conductors but not grounding conductors.
Click to expand...

Yes, and ty. and ty all for the replies. Funny enough, the light I Installed last week, the homeowner didnt like it, so she bought a different one and had us install it today. Grounds were physically tied together as well as around both box and tie bar bonding screws.
 
I generally ignore the ground screw on the "tie bar" unless mounted to a non metallic box. I figure it is bonded by it's mounting means on a metal box.

One thing you can't do is pigtail all the grounding conductors into one connector, if there are feed through conductors to other wiring components, this would potentially interrupt grounding continuity to feed thru if you removed the luminaire (or device), you need a pigtail or other separate connection point for local luminaire or device grounding conductor.
 
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