||09-11-2012 07:31 PM
Originally Posted by amakarevic
I was wondering if every metal receptacle need to be grounded via a green ground screw screwed in a hole in the back and connected to the other ground wires coming into and out of the box, in addition to the ground terminal of the possible power outlet or light for which the box is used. Also, if the box is used only as a JB, does it still need to be grounded?
Your title asks one question and your post asks another.
Does every metal box need to be grounded.....I would say yes. We could argue about special circumstances, but the rule is yes.
Your post asks if every metal receptacle needs to be grounded...I would say yes. A receptacle is not a box. Do you have to use the the green ground screw in the back of a metal box to ground a receptacle? Not necessarily. Some receptacles are self grounding. You could use a self grounding receptacle and attach it to a grounded box and would be fine.
Does a metal box containing wires that is just used as a junction box need to be grounded...Yes. I would use the equipment grounding conductor you pulled with the circuit and bond that to the back of the box via the pre-drilled and tapped hole that is provided.
Now, if you use metal conduit and properly connect your fittings to your metal boxes, then you would not have to use a green ground wire with your circuit. Your conduit would be your equipment ground and would take the place of the green ground wire. But you still would have to connect any grounding means from a light fixture, receptacle, etc to the back of the metal box via the pre-drilled and tapped hole that is provided.
Lets make this real simple. ALL METAL boxes, conduit, etc used in an electrical system needs to be grounded. How you ground them is where it gets interesting.