Grounding outlet box with pigtail

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Devinp

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Im having a debate with someone. We ran mc through a drop ceiling into a outlet box in a wall. Does there have to be a ground (pigtail) from the receptacle to the box itself?
 
Part of the wording in 240.146 is as follows:
A listed exposed work cover shall be permitted to be the grounding and bonding means when (1) the device is attached to the cover with at least two fasteners that are permanent (such
as a rivet) or have a thread locking or screw or nut locking means and (2) when the cover mounting holes are located on a flat non-raised portion of the cover.

Noted afterward...
see this thread:http://forums.mikeholt.com/showthread.php?t=187171
 
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Devinp said:
Im having a debate with someone. We ran mc through a drop ceiling into a outlet box in a wall. Does there have to be a ground (pigtail) from the receptacle to the box itself?
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The box is recessed? If so you can connect the cable EGC to the box and use a self-grounding device without a bonding jumper.
 
Devinp said:
Im having a debate with someone. We ran mc through a drop ceiling into a outlet box in a wall. Does there have to be a ground (pigtail) from the receptacle to the box itself?
Click to expand...
for the purposes of your debate, you have to understand the properties of the specific MC cable that you installed. What kind of MC did you run through the drop ceiling? Some types of MC have a discrete insulated grounding conductor (EGC - Equipment Grounding Conductor), while other types of MC have sheaths that are listed as EGCs. Without the manufacturer's installation instructions for your installed cable, you will be debating from the kitchen table how many teeth are in the pastured horse's mouth.

Also, if the MC sheath is an EGC, the MC cable connector at the box must be listed for bonding the EGC of the MC to the box.

You say "outlet box in a wall." To me, that says you installed an "old work" box in the wall and that the new receptacle device and cover plate are flush with the finished surface of the wall. If the receptacle device you installed was an auto grounding device, then no additional bonding is necessary. Spend some time with 250.146 for the rules.
 
Knuckle Dragger said:
I have been doing it this way so long that I forget if it is NEC compliant or not but we typically ground the receptacle to the egc which is grounded the metal box.
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You have it backwards. You have to ground the box, then to the receptacle with a jumper if you're not using a self grounding device or a cover that qualifies as grounding the receptacle when done as required.
 
Little Bill said:
You have it backwards. You have to ground the box, then to the receptacle with a jumper if you're not using a self grounding device or a cover that qualifies as grounding the receptacle when done as required.
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I agree the box must remain grounded even if the device is removed {250.148(B)}. I would add that when doing this way for switch boxes that the switches are not required to be self-grounding.

250.148(B) Grounding Continuity. The arrangement of ground-ing 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.
Click to expand...
 
al hildenbrand said:
for the purposes of your debate, you have to understand the properties of the specific MC cable that you installed. What kind of MC did you run through the drop ceiling? Some types of MC have a discrete insulated grounding conductor (EGC - Equipment Grounding Conductor), while other types of MC have sheaths that are listed as EGCs. Without the manufacturer's installation instructions for your installed cable, you will be debating from the kitchen table how many teeth are in the pastured horse's mouth.

Also, if the MC sheath is an EGC, the MC cable connector at the box must be listed for bonding the EGC of the MC to the box.

You say "outlet box in a wall." To me, that says you installed an "old work" box in the wall and that the new receptacle device and cover plate are flush with the finished surface of the wall. If the receptacle device you installed was an auto grounding device, then no additional bonding is necessary. Spend some time with 250.146 for the rules.
Click to expand...

For the record, this is MCI-A listed MC.
 
Sorry for the confusion gents.
It was supposed to be "typically ground the receptacle to the egc which is grounded to the metal box."
I just worded it working backwards.
 
I could swear I read somewhere in the code that the box is grounded if you ground the egc to the receptacle ground and remove the little cardboards from the receptacle screws....
 
newservice said:
I could swear I read somewhere in the code that the box is grounded if you ground the egc to the receptacle ground and remove the little cardboards from the receptacle screws....
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That can work if the receptacle is specifically listed as self grounding.

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newservice said:
I could swear I read somewhere in the code that the box is grounded if you ground the egc to the receptacle ground and remove the little cardboards from the receptacle screws....
Click to expand...

GoldDigger said:
That can work if the receptacle is specifically listed as self grounding.

Sent from my XT1585 using Tapatalk
Click to expand...

mopowr steve said:
Yes, I read that too at one time. And, as long as the device yoke seats against the box.
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Again, you have this backwards. I don't know of any case where you aren't required to ground the box directly. When the box is grounded, you can omit the bonding jumper to the receptacle if you follow the requirements.
(A) Surface-Mounted Box. Where the box is mounted on
the surface, direct metal-to-metal contact between the device
yoke and the box or a contact yoke or device that
complies with 250.146(B) shall be permitted to ground the
receptacle to the box. At least one of the insulating washers
shall be removed from receptacles that do not have a contact
yoke or device that complies with 250.146(B) to ensure
direct metal-to-metal contact. This provision shall not apply
to cover-mounted receptacles unless the box and cover
combination are listed as providing satisfactory ground
continuity between the box and the receptacle. A listed
exposed work cover shall be permitted to be the grounding
and bonding means when (1) the device is attached to the
cover with at least two fasteners that are permanent (such
as a rivet) or have a thread locking or screw locking means
and (2) when the cover mounting holes are located on a flat
non-raised portion of the cover.
Click to expand...
 
Little Bill said:
Again, you have this backwards. I don't know of any case where you aren't required to ground the box directly. When the box is grounded, you can omit the bonding jumper to the receptacle if you follow the requirements.
Click to expand...
I think that a good way to remember the correct direction of the self-grounding is to think that the removal of the device cannot interfere with the mandatory EGC connections.
 
ActionDave said:
No. You have to tag the box with an EGC, you may or may not need to tag the device.
Click to expand...

Little Bill said:
Again, you have this backwards. I don't know of any case where you aren't required to ground the box directly. When the box is grounded, you can omit the bonding jumper to the receptacle if you follow the requirements.
Click to expand...

I agree with both of you. You ground the box and then you might need a bonding jumper to the device depending on certain conditions. Even if you use a metal raceway that qualifies as an EGC (like EMT) you still need to connect a wire type EGC to the box if you use one in the raceway.
 
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