DIY Home Improvement Forum banner

does every metal box need to be grounded?

35K views 46 replies 14 participants last post by  brgmgb 
#1 ·
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?

Thanks
 
#12 ·
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.
 
#15 ·
Your title asks one question and your post asks another.

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.
250.146 says that an equipment bonding jumper shall be used to connect the grounding terminal of a grounding type receptacle to a grounded box unless, it is a surface mounted box where you have direct metal to metal contact between the device yoke and the box.
 
#28 ·
Grounded, bonded, to the layman they are the same thing, but many electricians do not know the difference either.

The green wires you buy that comes with the screw is called a bond jumper, at least in my neck of the woods.
 
#40 · (Edited)
amakarevic said:
what can happen if a metal receptacle is NOT grounded but the outlet or light that it is used for is?
Receptacles receive things. Outlets provide things. Lights are installed at outlets. So are receptacles.

I think what you mean to ask is, what if an outlet box is not bonded, but the device attached to the outlet box is bonded.

Answer: .....it depends.

Is the device self bonding?
Is there a fault?
Who is on first?
 
#41 ·
Receptacles receive things. Outlets provide things. Lights are installed at outlets. So are receptacles.
by "receptacle" i mean just a metal box.
by "outlet" i mean a power outlet, usually a duplex, AKA socket, into which you put the plug from a device or an appliance.
a "light" would be anything that provides illumination and is mounted to a receptacle.
so a receptacle most commonly hosts either an outlet, a light, or is a junction box

sorry for any confusion
 
#47 ·
I think all of his questions have been answered, but not in one post. I'll attempt to do that.

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
By receptacle, the OP meant box. It was also established that the ground/bond screw does not have to be green. It also is implied in the answers that it is no good to just put in a screw if you do not connect it back to the grounding conductor coming into the box. The question is, "Does every metal box need to be grounded via a screw in the hole in the back of the box?" For safety, yes.

...in addition to the ground terminal of the possible power outlet or light for which the box is used.
If the "device yoke" is in contact with the metal box, then you probably do not need to run a ground wire to the device's ground screw. But if in doubt, running the extra conductor will not do any harm.

Also, if the box is used only as a JB, does it still need to be grounded?
I would ground the junction box for the same reason as in question #1. If the bare hot wire comes in contact with the metal box, someone touching the box could receive a nasty shock. In the junction box, you'll wire nut the ground conductors anyway. Just add one more as a jumper/pigtail to the box's ground screw.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top