Grounding metal boxes

[bronc076]

Been watching a lot of videos as I'll be wiring my shop this summer and though I learned a lot from Dad who was an electrician back in the day there are a lot of requirements I need to get up to speed on as we don't have inspection here and I want to do it correctly. Even picked up the 2023 code book, that's a real page turner....

Anyway, I just watched a video where a guy is installing a metal box with a standard 120V receptacle fed by romex. He hooked the receptacle up as expected. He also said it is required to run a wire from the ground to the metal box, so he took the ground from the romex, spliced it to two pigtails, hooked one to the box and one to the receptacle. I get that the metal box needs to be bonded but I thought the act of screwing the receptacle to the box was sufficient to bond it. When you install with conduit, no ground wire is needed as the network of metal conduit provided the path for fault current back to the panel, and the ground pin on the receptacle is connected by screwing the receptacle into the box. Does code require a pigtail from the ground to the metal box, or is screwing the receptacle into the box sufficient?

Then he goes on to say that the connection to the receptacle may not be needed if you connect the ground to the box, but only with commercial grade outlets. Not sure this guy has any business putting how to videos on the internet. Never heard of an outlet that didn't have a connection from the ground pin to the mounting ears.

I'll be wiring my shop this summer and I was going to hook the ground wires to the green screws on the outlets, do I also need a pig tail to the box, or do I hook it to the box and just screw the outlet in? What is common practice, we don't have inspections out here in the county, so I'm looking for the commonly accepted method of doing it.

Shop will be stud walls covered in plywood so I'm pretty sure Romex is fine as it will not be exposed. Outside of the building is sheet metal. Maybe I should just run MC as I prefer metal boxes and won't have to deal with ground wires.

Thanks
Rob


I'll dig through my 2023 code book and see what I can find.

Link to video

 

[mm08822]

Been watching a lot of videos as I'll be wiring my shop this summer and though I learned a lot from Dad who was an electrician back in the day there are a lot of requirements I need to get up to speed on as we don't have inspection here and I want to do it correctly. Even picked up the 2023 code book, that's a real page turner....

Anyway, I just watched a video where a guy is installing a metal box with a standard 120V receptacle fed by romex. He hooked the receptacle up as expected. He also said it is required to run a wire from the ground to the metal box, so he took the ground from the romex, spliced it to two pigtails, hooked one to the box and one to the receptacle. I get that the metal box needs to be bonded but I thought the act of screwing the receptacle to the box was sufficient to bond it. When you install with conduit, no ground wire is needed as the network of metal conduit provided the path for fault current back to the panel, and the ground pin on the receptacle is connected by screwing the receptacle into the box. Does code require a pigtail from the ground to the metal box, or is screwing the receptacle into the box sufficient?

Then he goes on to say that the connection to the receptacle may not be needed if you connect the ground to the box, but only with commercial grade outlets. Not sure this guy has any business putting how to videos on the internet. Never heard of an outlet that didn't have a connection from the ground pin to the mounting ears.

I'll be wiring my shop this summer and I was going to hook the ground wires to the green screws on the outlets, do I also need a pig tail to the box, or do I hook it to the box and just screw the outlet in? What is common practice, we don't have inspections out here in the county, so I'm looking for the commonly accepted method of doing it.

Shop will be stud walls covered in plywood so I'm pretty sure Romex is fine as it will not be exposed. Outside of the building is sheet metal. Maybe I should just run MC as I prefer metal boxes and won't have to deal with ground wires.

Conduit run on the surface using steel 4" sq boxes and steel raised covers provides a direct surface-surface contact. If the receptacle is attached to the cover with 2 or more screws it is then considered grounded via the cover which is attached via 2 screws to the box. The metallic conduit may or may not have a grd wire in it. The conduit alone is permitted to act as the grounding path back to the panel.

In the case of using a mud ring (as shown in video thumbnail), there is no definite assured contact between the metal box/mudring and receptacle strap because of the wall finish material compromising a similar surface-surface contact. This requires a ground wire back to the steel box/grounding conductors.

I usually tie the grd wire (from the cable feeding the box ) around the box grd screw and leave it long enough to wirenut to any other ground wires of cables leaving the box.

Each device should have its own grd wire or loop between multiple devices. In no case shall removing any device compromise the connection of any other grd wire.

I didn't check the video.

 

[WildBill]

I always run a ground and ground to the box even though technically I don't have to. I don't want to hope nothing corrodes, comes apart, gets modified, etc. in the future that would effect the grounding. Its easy, cheap, and fast to do so I figure why not. Maybe if I was installing hundreds of metal boxes on a regular bases I would have a different opinion though.

 

[dave*99]

'll be wiring my shop this summer and I was going to hook the ground wires to the green screws on the outlets, do I also need a pig tail to the box, or do I hook it to the box and just screw the outlet in? What is common practice, we don't have inspections out here in the county, so I'm looking for the commonly accepted method of doing it.

I usually tie the grd wire (from the cable feeding the box ) around the box grd screw and leave it long enough to wirenut to any other ground wires of cables leaving the box.

Yup

Or long enough to go to the device if there are no cables leaving the box.

 

[sparky 1971]

I usually tie the grd wire (from the cable feeding the box ) around the box grd screw and leave it long enough to wirenut to any other ground wires of cables leaving the box.

I don't have a 2023 code book yet because it looks like we aren't going to adopt it until late 2025 if at all. I did take a 2023 update class to get six of my 18 hours of continuing ed out of the way though. In the class, we were told that won't fly any longer. There has to be a separate wire attached to the ground screw, then that will be connected to the grounds of the branch circuits as well as the devices.

 

[mm08822]

I don't have a 2023 code book yet because it looks like we aren't going to adopt it until late 2025 if at all. I did take a 2023 update class to get six of my 18 hours of continuing ed out of the way though. In the class, we were told that won't fly any longer. There has to be a separate wire attached to the ground screw, then that will be connected to the grounds of the branch circuits as well as the devices.

I went through the 2023 NEC and can't find anything specifying that. The closest I found was a jumper from metal box to device when using a mud ring - that is nothing new.

Any code reference for that requirement?

 

[sparky 1971]

I went through the 2023 NEC and can't find anything specifying that. The closest I found was a jumper from metal box to device when using a mud ring - that is nothing new.

Any code reference for that requirement?

I don't have anything. Usually we adopt the newest code one year after it comes out, the 2023 would normally go into effect on Jan. 1, 2024. The first thing the instructor said was that if it gets adopted at all, it wouldn't be until the latter half of 2025. I stopped paying attention shortly thereafter and waited patiently for the catered bbq dinner to come.

The only other thing I remember is that kitchen islands will no longer be required to have receptacles, but the ability to add them must be in place. A junction box with wires in it is all that will be needed.

 

[u2slow]

Normally wrap the incoming cable's bond wire on the screw and land the loose end on the receptacle. Pigtail it instead if another run leaves the box.

The newest Code doesn't matter much in this case .... since without permit/inspection there's no exact record of when it was done.

 

[mm08822]

For those who get spections, it do. (Assuming they open dem boxes)

 

[exranger06]

Anyway, I just watched a video where a guy is installing a metal box with a standard 120V receptacle fed by romex. He hooked the receptacle up as expected. He also said it is required to run a wire from the ground to the metal box, so he took the ground from the romex, spliced it to two pigtails, hooked one to the box and one to the receptacle. I get that the metal box needs to be bonded but I thought the act of screwing the receptacle to the box was sufficient to bond it. When you install with conduit, no ground wire is needed as the network of metal conduit provided the path for fault current back to the panel, and the ground pin on the receptacle is connected by screwing the receptacle into the box. Does code require a pigtail from the ground to the metal box, or is screwing the receptacle into the box sufficient?

You have that backwards. The metal box primarily gets the ground wire attached first. A bonding wire is then run from the box to the receptacle, if the receptacle isn't already bonded to the box via the mounting screws. 250.148(B) says "the arrangement of grounding conductors shall be such that the disconnection or removal of a luminaire, receptacle, or other device fed from the box does not interrupt the electrical continuity of the equipment grounding conductor(s) providing an effective ground-fault current path." If you only connect the ground wire to the receptacle and not the box, and rely on the mounting screws to bond the box, then the box will not be grounded if you remove the receptacle. Bonding to the box first ensures it stays grounded if you remove the receptacle.

250.146(A) says that a receptacle doesn't need a ground wire if it's connected to a surface-mount metal cover and box (and the box is already grounded, which it should be - see above). Note that that applies only to surface mount boxes, not flush boxes.

250.146(B) says that a receptacle doesn't need a ground wire in a flush mount box IF:
1. the box is already grounded
AND
2. The receptacle is a listed self-grounding type. A self-grounding receptacle has a metal clip around one of the mounting screws that ensures good electrical continuity between the screw and the yoke, like this one:

If the receptacle is not a self-grounding type, then you have to install a bonding jumper between the receptacle and the flush-mount box, even if the yoke is making contact with the metal box.

Then he goes on to say that the connection to the receptacle may not be needed if you connect the ground to the box, but only with commercial grade outlets. Not sure this guy has any business putting how to videos on the internet. Never heard of an outlet that didn't have a connection from the ground pin to the mounting ears.

I believe by "commercial grade" he was referring to self-grounding receptacles. If so, he's right.

 

[BreeStephany]

The metal box / enclosure must be bonded to ground, which is done via a pigtail to the box. If box fill is a concern, you can also take the solid ground from one of the romex, wrap it around the ground screw in the box and then bring your grounds together, but given that you will likely only have a single 12-2 in and a single 12-2 out, box fill likely won't be an issue and grounding pigtails help speed up the process. Grounding pigtails to the receptacle are required because the receptacle must be SOLIDLY bonded. A common issue with 4-square metal boxes when mudrings are used behind ply, sheetrock, etc. is that the mudring is often somewhat recessed / not perfectly flush, so without a pigtail, the ground path is relying SOLELY on the 6-32 screws of the device to provide the path to ground and if the receptacle is loose and does not have a solid fit to the mudring, it does not provide a SOLID bond path to ground, thus the requirement for a grounding pigtail from the device to your grounding conductor.

I believe it is the same thought process for industrial raised covers on 4-squares. If the screws mounting the raised cover or device loosen, your solid bond to ground can be lost to the device, thus having a grounding pigtail ensures a solid path to ground at all times.

Just my two cents.

 

[bronc076]

Looking at my code book it looks like I also need to remove one insulating washer.

Thanks all for the input and thanks exranger for the code reference. That all makes perfect sense.

I run a team that conducts cybersecurity assessments for a living and any time we tell someone they are not meeting a requirement we specify the section of the appropriate Army/DoD directive or regulation for reference.

 

[kaffine]

Never heard of an outlet that didn't have a connection from the ground pin to the mounting ears.

Isolated ground outlets are used for some applications the box has a ground wire that goes back to the panel and then another ground wire connects to the outlet. I've had some equipment that wants isolated ground as they think it will reduce electrical noise. I also think it is somewhat common for hospitals to use isolated grounds.

I have always hated working with isolated ground systems they never end up as isolated as they think it will be.

 

[dave*99]

The only other thing I remember is that kitchen islands will no longer be required to have receptacles, but the ability to add them must be in place. A junction box with wires in it is all that will be needed.

I know this is a bit off topic, but I read that section too and was surprised we can no longer put a receptacle on the side of the island cabinet below the worksurface. 2023 code says IF you do install the island receptacle, it must be in or above the worksurface. And the housing must be listed for that installation.

"As part of its substantiation for the change, NEC Code Making Panel 2 cited Consumer Product Safety Commission (CPSC) data showing that between 1991 and 2020, an estimated 9,700 people, many of them children, were treated in United States emergency departments for burns and other injuries after pulling on or running into power cords plugged into receptacle outlets installed below island and peninsula work surfaces."

Kitchen Island and Peninsula Outlets and the NEC

Learn more about how the current and past three editions of the NEC address kitchen island and peninsula receptacle outlets.

www.nfpa.org

 

[bronc076]

Speaking of islands (Is it wrong to hijack my own thread?) we just had our kitchen remodeled and I wired the island. There are two outlets, one hidden in an appliance garage (I think that's the term used in the code book) for the microwave and one on the side of the island. Does The hidden one also need to be GFCI, or just the one easily accessible? I'm thinking it does, and the island is on its own breaker so I'm planning to just install a GFCI breaker. But if the microwave does not require GFCI I'll just replace the one outlet. MO is not on 2023 code and out in the county there is no such thing as electrical inspection. That's why I bought a code book so I can try to look this stuff up but there is a lot of info in there.

Thanks!

 

[u2slow]

Around here, the code cycle in force goes back to the last documented electrical installation under a permit (with respect to the kitchen). If thats when the house was built, thats it.

 

[bronc076]

That's the problem, where I live there is no such thing as a permit for electrical, example: I'm having a shop built, the permit costs $18 and the county checks setback, then when it's built they verify the building is the correct size and location, then they assess it and my taxes go up accordingly. No concrete, framing, plumbing, or electrical Inspections like when I built my shop in AZ. I live out in the county. I'm trying to do it all correctly and professional for safety, and so when we sell the place there are no issues. So I'm going by current code where it makes sense as that's the book I bought. I bring up questions here and get opinions and industry practices, as well as enjoy the debates, banter, and war stories.

Personally I disagree with code eliminating the outlet on the side of the island. Just because people have accidents due to poor practices or judgement does not make something dangerous.

 

[sparky 1971]

Speaking of islands (Is it wrong to hijack my own thread?) we just had our kitchen remodeled and I wired the island. There are two outlets, one hidden in an appliance garage (I think that's the term used in the code book) for the microwave and one on the side of the island. Does The hidden one also need to be GFCI, or just the one easily accessible? I'm thinking it does, and the island is on its own breaker so I'm planning to just install a GFCI breaker. But if the microwave does not require GFCI I'll just replace the one outlet. MO is not on 2023 code and out in the county there is no such thing as electrical inspection. That's why I bought a code book so I can try to look this stuff up but there is a lot of info in there.

Thanks!

GFCI protection is required for receptacles within 6' of a sink as well as all that are serving the counter top. The microwave doesn't need GFCI unless it is within 6' of the sink. If you are really wanting to be "up to code", they are supposed to have AFCI protection as well. Use a combination AFCI/GFCI breaker.

 

[sparky 1971]

Personally I disagree with code eliminating the outlet on the side of the island. Just because people have accidents due to poor practices or judgement does not make something dangerous.

Islands are running out of places to put a receptacle. Full length drawers and width drawers are eating up all of the space where a cut in box needs to recess. Almost all islands have an overhang and the receptacle can't go under that because appliance cords are too short. Pop ups don't always work because it will hang down into a drawer, keeping the drawer from being able to open.

 

[bronc076]

GFCI protection is required for receptacles within 6' of a sink as well as all that are serving the counter top. The microwave doesn't need GFCI unless it is within 6' of the sink. If you are really wanting to be "up to code", they are supposed to have AFCI protection as well. Use a combination AFCI/GFCI breaker.

Thanks Sparky! I'll go GFCI breaker because of the 6' rule. I'm not sure I can wrap my head around the true benefit of AFCI. It all makes sense on paper but perhaps the standards making people are running out of real requirements to write down. AFCIs in my GF's house in AZ seemed to be failure prone. If at selling time a future home inspection reveals AFCI is needed it's an easy breaker swap, but for now I'll stick with traditional safety as in the kitchen she uses metal appliances, sometimes with wet hands. Only way to protect both because of wire routing is with a breaker or hide the GFCI outlet behind the microwave and that would be stupid.

 

[exranger06]

NEC 2020 requires GFCI only for countertops and within 6' of the sink. 2023 NEC requires GFCI on ALL kitchen receptacles, regardless of location. And that includes the 240V receptacle for the oven.

 

[bronc076]

It's only a matter of time before someone comes up with a "smart panel" that uses AI to determine usage trends on each circuit and cuts power when it thinks something is dangerous.

sigh

So I typed that as a joke, then before I hit post I decided to google "smart electric panel."

SPAN® Panel | Lower your energy bill

SPAN Panel is a re-invention of the 100 yr old home electrical panel adding a layer of intelligence and control to your home.

www.span.io

 

[u2slow]

That's the problem, where I live there is no such thing as a permit for electrical....

Personally I disagree with code eliminating the outlet on the side of the island.

Its not a problem, its a freedom. Your island receptacle must have preceded the new rule.

 

[sparky 1971]

Its not a problem, its a freedom. Your island receptacle must have preceded the new rule.

Most places haven't adopted the 2023 NEC yet, I looked and it appears that only four states are on it as of 7-1-2023. 27 are on the 2020, 12 are on the 2017, one o n the 2014, and two are still on the 2008.

https://www.nfpa.org/education-and-research/electrical/nec-enforcement-maps