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Discussion Starter · #1 ·
I am adding a subpanel and some outlets in my garage, everything is surface mounted. I initially plan to just use the EMT conduit and metal box as ground without running ground wire, but some people here recommend running one ground wire just for another level of protection.

As shown in the picture, there are two 240v circuits with additional 120v circuits sharing the 3/4 conduit. One 10# stranded ground wire. what's the best way to connect this ground wire?

All my receptacles can be used as self grounded to metal box without running additional ground wire. Should I just make a loop of the ground wire and secured it with ground screw to the box and without running ground wire to the receptacle? Or should I cut the ground wire and joint multiple ground wire and then use a pigtail to metal box screw and to the receptacle ground screw? If it's possible, I would rather not using ground wire connect to the receptacle because it's easier to do and save space in the box. In addition, I don't have extra green ground wire left. If I need to add pigtail, could I use bare copper wire?

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You can ground any box you please, or none at all. If you want to ground a box, the ground wire must have 6" of free length in the box, just like any other wire you might splice here.

Since it's stranded wire, that is a royal PITA to put on a screw (it tends to birdcage when you tighten the screw, so unless you master that, don't do it). Also, once you correct your slack issue, you'll have 2 wires to attach to 1 screw. So I would just pigtail off that screw with a #10 solid ground wire and join it to the others with a large (red or green) wire nut. If you want to have a pajama party with every receptacle getting grounded, feel free... this would be a good application for a green wire nut with one #12 ground wire run all the way through the nut, giving a #12 pigtail at each end.

The bigger problem I see in this box is you're trying to cram a GFCI device into a 4x4 box using a 2-gang cover. That is going to be a nightmare, because in 2-gang mode, there is bupkus for clearance around the GFCI device. You have a deep box but that does nothing for the side clearance of the GFCIs. I would either

  • Change the 2-gang cover for a 1-gang cover, eliminating the second receptacle altogether.
  • Move the GFCI protection closer to the panel, using its downline protection feature there. Now you can use 2 plain outlets, and those fit fine in a 4x4.
  • Change the 4x4 junction box to a 4-11/16" square junction box with 2-gang domed cover. That will fit nicely, and it's what I would have recommended in the first place. Those boxes are considerably cheaper at real electrical supply houses. The big-box stores want $5-7 for them for some reason. (because they gotcha, and they know it, same way they overcharge on a lot of less popular stuff.)
 

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Discussion Starter · #4 ·
You can ground any box you please, or none at all. If you want to ground a box, the ground wire must have 6" of free length in the box, just like any other wire you might splice here.

Since it's stranded wire, that is a royal PITA to put on a screw (it tends to birdcage when you tighten the screw, so unless you master that, don't do it). Also, once you correct your slack issue, you'll have 2 wires to attach to 1 screw. So I would just pigtail off that screw with a #10 solid ground wire and join it to the others with a large (red or green) wire nut. If you want to have a pajama party with every receptacle getting grounded, feel free... this would be a good application for a green wire nut with one #12 ground wire run all the way through the nut, giving a #12 pigtail at each end.

The bigger problem I see in this box is you're trying to cram a GFCI device into a 4x4 box using a 2-gang cover. That is going to be a nightmare, because in 2-gang mode, there is bupkus for clearance around the GFCI device. You have a deep box but that does nothing for the side clearance of the GFCIs. I would either

  • Change the 2-gang cover for a 1-gang cover, eliminating the second receptacle altogether.
  • Move the GFCI protection closer to the panel, using its downline protection feature there. Now you can use 2 plain outlets, and those fit fine in a 4x4.
  • Change the 4x4 junction box to a 4-11/16" square junction box with 2-gang domed cover. That will fit nicely, and it's what I would have recommended in the first place. Those boxes are considerably cheaper at real electrical supply houses. The big-box stores want $5-7 for them for some reason. (because they gotcha, and they know it, same way they overcharge on a lot of less popular stuff.)
Thank you. I have no interest in pajama party. If it's too much work, I would rather pull out the ground wire and don't use the ground wire at all is that's OK. #10 solid wire is very stiff I would rather not using it unless necessary.

You are absolutely right about the GFCI device. I initially want to get the 4-11/16" larger box but the large box from homedepot only has 1" knockout. I really don't like to use 1" EMT conduit. So I choose the 4x4 x 2 1/8" box. It's deep and I feel it has plenty room. I removed the yoke from the GFCI receptacle so the side clearance is not an issue any more. The problem is the top and bottom clearance of the GFCI receptacle so I bent the top and bottom protruded little strap of the GFCI receptacle and it fit in nicely without any problem. You see it from the picture that I bent the strap. If I change to 1-gang cover and eliminating the second receptacle, I still have the same issue of the bottom and top clearance and I still have to bent the strap.

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Discussion Starter · #5 ·
Bare wire is fine for a ground. I prefer a ground wire, but not manditory as long as you make good tight connections.
FYI, you should loop wire passing thru a box. Takes little space and you will have slack if needed in the future.
Thank you. The #10 wires are for the 30 amp 240v receptacle at the end. So I just let it running through the box. I might like to loop wire for the #12 wires but I am kind of running out of the wire actually. I bought 100 ft #12 black wire just barely enough. When I bought the wire, the next size package from homedepot is 250ft. But I only need probably 101 or 102 feet.
 

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Discussion Starter · #6 · (Edited)
Another question. The green ground wire is #10 wire because I was told to match the largest wire in the conduit for the ground wire. But most of the other box with receptacle are actually 20 amp receptacle. If I use pigtail, could I use #12 ground wire for pigtail?

Since the ground wire is not mandatory with EMT conduit connection and everything is already grounded, my understanding is that whatever way and whatever wire I use for ground wire connection is all redundancy and exceed the NEC requirement, and shouldn't cause any problem?
 

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Discussion Starter · #7 ·
Home depot selling this 2 GFCI Outlet Exposed Work Cover that is the same size as I use. If it's labeled as 2 GFCI outlet cover, that means that it's designed to accept GFCI receptacle in 4x4 box. I really wish I could add 4 receptacles in one 4x4 box.

 

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Discussion Starter · #8 ·
I just got home and did some measurement. I put a sample plate touching the side of GFCI receptacle, there is still a gap between the screw and the plate, given the fact that the GFCI receptacle will not touch the box, I feel there is good gap on the side of GFCI receptacle. I then tightened a #12 wire to both the GFCI and regular receptacle. The distance between the screw from receptacle and the side of cover is 6/16" for the regular receptacle, and 5.5/16" for the GFCI, not a big difference. Is there any rules that GFCI receptacle has to have a minimum gap from the electric box? I have several GFCI receptacles in my kitchen that using the 2 gang cover. I assume that's probably OK?

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If the box is to shallow for the two receptacles you can use and extension ring to make the box deeper. I personally would just use the box you have. The raised cover alone does help. But there are options to make this easier for you.
I always pull a ground wire. I know its not required with metal boxes and metal conduit. There have been instances where the conduit separates and then you have no ground anymore. In your particular instance its not likely to happen.
The work looks good.
 

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Discussion Starter · #12 ·
If the box is to shallow for the two receptacles you can use and extension ring to make the box deeper. I personally would just use the box you have. The raised cover alone does help. But there are options to make this easier for you.
I always pull a ground wire. I know its not required with metal boxes and metal conduit. There have been instances where the conduit separates and then you have no ground anymore. In your particular instance its not likely to happen.
The work looks good.
Thank you. The box is 2 1/8" that is deep enough. I eventually choose just screw the ground wire to the box instead of using pigtail to both box and receptacle as I found a previous advice from here, ground the box instead of receptacle athough the box is already grounded, but another connection doesn't hurt. Once I screw the receptacle to the cover, there is very tight connection between the receptacle and box with cover and I feel comfortable that there is very good connection for grounding. This avoid me using the wire nut to pigtail the ground wires which save a lot of space inside the box. I also move the GFCI receptacle to the left side so the hot wire is in the middle instead of side, less chance to touch the box.
 

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Home depot selling this 2 GFCI Outlet Exposed Work Cover that is the same size as I use. If it's labeled as 2 GFCI outlet cover, that means that it's designed to accept GFCI receptacle in 4x4 box. I really wish I could add 4 receptacles in one 4x4 box.

Do you mean 4 duplex receptacles with 2 individual receptacles on each yoke, or do you mean 4 duplex receptacles for a total of 8 receptacles?
The latter would take a four gang box. You can install box bars to mount ganged device boxes.
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If you cannot find the straps locally buy any fairly thin flat bar strap and put the boxes to the straps with self tapping screws. You can bend the strap to fit between the studs so that the strap will be flush with the stud faces and there won't be any bulge in the plaster. Screw the 2 ends which you bent to fit to the side of the studs

Set 2 box support straps a box height apart vertically and assemble the number of gangs you need by taking one or both sides off and putting them back together as one box. If you really want to have 4 duplex receptacles you will need 4 gang boxes. Some will say that I'm crazy but when I did that I did not use boxes with internal cable clamps. The 3X2X3-/2 deep boxes give you a lot of room. The edges of the sheet metal clamps can tear up wire insulation.
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Using 2 straps with only the height of the box in between gives you a quick and painless mounting task. Remember to set the ears for the depth of the wall covering.

There are wider box support straps that are easier to set for depth and fasten to the studs. You then fasten the box/es to the front of the strap by running 2 screws through the holes in the back of the box.

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Thank you. I have no interest in pajama party. If it's too much work, I would rather pull out the ground wire and don't use the ground wire at all is that's OK. #10 solid wire is very stiff I would rather not using it unless necessary.
I don't bother running grounds inside EMT, except between two boxes where I feel a run might suffer physical damage (forklift strike, duct above it falling down, etc.)

Even though grounds are not required, any grounds which are there need to comply with Code. So if you want to tie a #10 ground to a box with a pigtail, it must be a #10 pigtail. I suggested solid for that since it'll be easier to put on the screw. I have also been known to use yellow crimp-on lugs, one advantage to those is you can stack 2 on a screw.


You are absolutely right about the GFCI device. I initially want to get the 4-11/16" larger box but the large box from homedepot only has 1" knockout.
That's a sourcing problem, dealing with big-box it's 10 times harder to find what you want. Once you graduate beyond Romex and plastic boxes, it's really worth finding an electrical supply that you like. you only have to do that once lol, then after that every visit is 5 minutes long from turning in their driveway to pulling back out onto the road. 3 minutes of that is shooting the breeze lol.

The problem is the top and bottom clearance of the GFCI receptacle so I bent the top and bottom protruded little strap of the GFCI receptacle and it fit in nicely without any problem. You see it from the picture that I bent the strap. If I change to 1-gang cover and eliminating the second receptacle, I still have the same issue of the bottom and top clearance and I still have to bent the strap.
Having to do that is one reason I prefer the 4-11/16" boxes. Which don't require that.
 

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Discussion Starter · #16 ·
It's all done. Everything works fine. Personally I feel there's plenty of room with this 4x4 box for GFCI receptacle. Since I didn't pigtail the ground wire only ground the box, and all the receptacles can be back connected and accept two wires for each connection, and tightened by side screw, I don't even need the twist-on wire nut which save a lot of room in the box. For the total six 4x4 box, I only used one wire nut. I really like the back connection of these receptacles. Thank you for everyone's advice.

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Thank you. The box is 2 1/8" that is deep enough. I eventually choose just screw the ground wire to the box instead of using pigtail to both box and receptacle as I found a previous advice from here, ground the box instead of receptacle although the box is already grounded, but another connection doesn't hurt. Once I screw the receptacle to the cover, there is very tight connection between the receptacle and box with cover and I feel comfortable that there is very good connection for grounding. This avoid me using the wire nut to pigtail the ground wires which save a lot of space inside the box. I also move the GFCI receptacle to the left side so the hot wire is in the middle instead of side, less chance to touch the box.
What follows is an educational point! I'm not sniping at anyone. There is one thing about your installation that I want to point out. The US National Electric Code forbids using a raised cover as an Equipment Grounding Conductor (EGC) Unless it meets the specific requirements in 250.146, as yours does. If it doesn't comply with these very specific requirements the receptacle grounding terminal must be connected to the EGC by a wire or other approved method.

"250.146 Connecting Receptacle Grounding Terminal to Box.

An equipment bonding jumper shall be used to connect the grounding terminal of a grounding-type receptacle to a grounded box unless grounded as in 250.146(A) through (D). The equipment bonding jumper shall be sized in accordance with Table 250.122 based on the rating of the overcurrent device protecting the circuit conductors.

(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 or nut locking means and

(The way I read (A)(1) is that locking washers would be enough to satisfy this.)
(2) when the cover mounting holes are located on a flat non-raised portion of the cover."

Like this one
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Not like this one. Automotive lighting Rectangle Gas Circle Auto part


The reason for the restriction is that common boxes and covers are made of mild steel and, even though they are galvanized, the connection between them will corrode open if the installation is not carefully done and both box and cover lend themselves to a lot of metal to metal contact area. The connection corroding open did not seem to happen if the cover had the more recently available recessed corners were the screw holes are because that avoided the box getting distorted out of contact with the open edge of the box. If the box and cover make continuous contact all the way around the connection between them holds up well.

What can I say. I have a need to stay curious and try to discover new things about what I'm doing. Before I would open a raised cover to work in that box, while I had my Vol-Con Audible out already to check that I had turned off the correct breaker, I often checked the continuity between a mounting screw of the cover and the receptacle cover screw. The older hands will remember that the receptacles were held to the back of the raised cover by its single threaded cover screw hole. If the connection was dubious by sight or continuity check I would improve it. If it was loose from it's cover I would conclude that the way it was being used tended to loosen it. I'd drill the 2 holes through the ones on the screw yoke and throw in 2 extra 6/32 screws and nuts. I wasn't more knowledgeable than many of the people I worked with. I just would get bored it I didn't keep actually looking at and thinking about the work more than just enough to install it. I think that is why I moved into fire alarm system and control work and also why I when on into remote, alternative power sourced, communications shelter installs all over this hemisphere of the globe.

You are going to support that EMT within 3 feet of every box aren't you?" That means any length more than 6 feet gets 2 clamps or straps.

Tom Horne
 

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Discussion Starter · #18 ·
What follows is an educational point! I'm not sniping at anyone. There is one thing about your installation that I want to point out. The US National Electric Code forbids using a raised cover as an Equipment Grounding Conductor (EGC) Unless it meets the specific requirements in 250.146, as yours does. If it doesn't comply with these very specific requirements the receptacle grounding terminal must be connected to the EGC by a wire or other approved method.

"250.146 Connecting Receptacle Grounding Terminal to Box.

An equipment bonding jumper shall be used to connect the grounding terminal of a grounding-type receptacle to a grounded box unless grounded as in 250.146(A) through (D). The equipment bonding jumper shall be sized in accordance with Table 250.122 based on the rating of the overcurrent device protecting the circuit conductors.

(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 or nut locking means and

(The way I read (A)(1) is that locking washers would be enough to satisfy this.)
(2) when the cover mounting holes are located on a flat non-raised portion of the cover."
Like this one
View attachment 674525 Not like this one. View attachment 674524

The reason for the restriction is that common boxes and covers are made of mild steel and, even though they are galvanized, the connection between them will corrode open if the installation is not carefully done and both box and cover lend themselves to a lot of metal to metal contact area. The connection corroding open did not seem to happen if the cover had the more recently available recessed corners were the screw holes are because that avoided the box getting distorted out of contact with the open edge of the box. If the box and cover make continuous contact all the way around the connection between them holds up well.

What can I say. I have a need to stay curious and try to discover new things about what I'm doing. Before I would open a raised cover to work in that box, while I had my Vol-Con Audible out already to check that I had turned off the correct breaker, I often checked the continuity between a mounting screw of the cover and the receptacle cover screw. The older hands will remember that the receptacles were held to the back of the raised cover by its single threaded cover screw hole. If the connection was dubious by sight or continuity check I would improve it. If it was loose from it's cover I would conclude that the way it was being used tended to loosen it. I'd drill the 2 holes through the ones on the screw yoke and throw in 2 extra 6/32 screws and nuts. I wasn't more knowledgeable than many of the people I worked with. I just would get bored it I didn't keep actually looking at and thinking about the work more than just enough to install it. I think that is why I moved into fire alarm system and control work and also why I when on into remote, alternative power sourced, communications shelter installs all over this hemisphere of the globe.

You are going to support that EMT within 3 feet of every box aren't you?" That means any length more than 6 feet gets 2 clamps or straps.

Tom Horne
Thank you. That's a good education. Looks like I need to buy more straps. The good thing about doing all these wiring by myself is that I know what I did and and I know what could go wrong and feel more comfortable how safe it is. I have checked the old wiring of my house and found tons of problem including many circuits have 14 awg wires with 20 amp breakers, almost all receptacles using push in back stab connection some connection already became loose, some multi wire branch circuits with two hot wires from the same phase, and some receptacles have no ground connection.

When I first bought the house, the general inspector proudly pasted his sticker on my main panel with his name and telephone number indicating that he has inspected the service panel. However, when I opened the panel cover, it clearly shows that two sets of black and red hot wires connected to the same phase of tandem circuit breaker. I can't believe that professional inspector could easily ignore or not notice these obvious problem. If I have not tried to do the wiring by myself and tried to understand the residential wiring, I might not realize all those potential problem in my house. It's definitely a worthwhile experience.
 
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