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I'm running a subpanel (new) back to my main area (main is full) so running it off another subpanel that was already there (old).

I really only need this to feed my welder which is 240v only (plug is hot/hot/ground). I planned to run the new 40A circuit off my subpanel, with 8/2 wire so hot/hot/uninsulated ground. I was about to connect it to my old subpanel but realized there's no connected ground in this panel as far as I can tell, only hot/hot/neutral bar (no bonding screw I think, could the box possibly be considered grounded because it's attached to the pain panel with a metal connector?). So two main questions:

  1. Can I connect the uninsulated ground wire (in the picture) for running my new subpanel (240v only) to the neutral bar?
  2. If the old subpanel is running 120v circuits above, I assume this panel needs to be grounded? The issue with running a new ground from the old subpanel back to the main is that I have no more neutral/ground slots on the main panel!

Appreciate any advice

enter image description here

enter image description here

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  • Waitaminute... this is for a computer server, not a welder? Why didn't you say so in the first place? Not sure it really makes a difference, but if you give incorrect details in your question, it's reasonable to expect incorrect answers...
    – FreeMan
    Commented Jul 1, 2022 at 16:51
  • Also, if you're installing a panel with a breaker to plug this into, and your main panel is full, and your existing sub panel is full, DON'T limit yourself to 240v only loads in this new panel, you (or future owners) will hate you for it. Spend the extra couple of bucks now to run a neutral to the panel so you can run 120v loads off it in the future, too.
    – FreeMan
    Commented Jul 1, 2022 at 16:53
  • Finally, are you sure those breakers in that first picture are the correct ones for this sub panel? They're not sitting square to the panel or each other which indicates they could be foreign breakers not approved/listed for this panel and, therefore, potential fire starters.
    – FreeMan
    Commented Jul 1, 2022 at 16:55
  • @FreeMan good point! I'll double check when I get home, but could be because I popped them all out to inspect the panel at one point or another I may have just not put it back in correctly
    – Azulith
    Commented Jul 4, 2022 at 3:15

3 Answers 3

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It appears that you have a metallic conduit and this can be the ground but it was not properly installed.

the TKO or knockouts alone don’t meet code so a grounding bushing or grounding lock nut are needed to bond the case and then the case is the proper location for a ground bond.

You can add a grounding buss bar or lugs to the case. In some cases 2 dimples next to a hole that a #10 grounding screw goes in is a normal case ground.

a proper ground requires a bushing or lock nut that has a wire clamp attached a wire Ty the frame to the clamp and it is a proper bond.

A #10 or larger wire would be plenty large enough, a piece of scrap feeder wire stripped works well if you don’t have 10.

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  • I've added a picture of the connection, let me know your thoughts.
    – Azulith
    Commented Jun 30, 2022 at 20:51
  • Looks right to me. I can count on one hand the number of ground wires I've ran. - "not properly installed... knockouts alone don’t meet code" ?
    – Mazura
    Commented Jun 30, 2022 at 20:58
  • I would reference 250.92.B then the exhibits 250.33, 250.34 and 250.35 , 250.36 When a service or sub is connected by pipe and I have seen many concentric and TKO that have totally broken free if no bonding bushing or locknut there would be no ground. The wedge can be added after the fact without opening everything up.
    – Ed Beal
    Commented Jun 30, 2022 at 22:32
  • Yes, an accessory ground bar is the right answer here. Commented Jul 1, 2022 at 2:05
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Metal conduit is used as ground, but you need to run metal conduit all the way to the welder receptacle, since no ground mounting in that box.

Ground and neutral must be separated in sub panels. They are only connected in the main panel.

I think you might be able to add a ground bar/mounting screw to the sub panel, but need the experts to say for sure.

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  • There is a ground bar in the subpanel, in fact there was one ground wire running to it from a 15a 120v circuit, but I thought maybe that was wired in error.
    – Azulith
    Commented Jun 30, 2022 at 20:13
  • So basically the new panel should be wired hot/hot to the double pole breaker, and ground to the ground bar in the subpanel?
    – Azulith
    Commented Jun 30, 2022 at 20:21
  • The picture only shows a neutral bar. Is there another bar in that sub panel for ground? If so you should be good to go, if you can fix grounding as mentioned in the other answers.
    – crip659
    Commented Jun 30, 2022 at 20:34
  • Yes, sorry there is another ground bar off to the left, not pictured. Thanks @crip659
    – Azulith
    Commented Jun 30, 2022 at 21:36
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"You should always make efforts to provide the safest possible path to ground though, do not clamp to oxidised/painted metal and do not weld in wet conditions." "some reasons for getting shocked. 1. bad ground of course" – Welding and risk of electric shock

OSHA says you need a wire.

https://www.osha.gov/laws-regs/regulations/standardnumber/1926/1926.351

1926.351 - Arc welding and cutting.

1926.351(c)(2)

Pipelines containing gases or flammable liquids, or conduits containing electrical circuits, shall not be used as a ground return. For welding on natural gas pipelines, the technical portions of regulations issued by the Department of Transportation, Office of Pipeline Safety, 49 CFR Part 192, Minimum Federal Safety Standards for Gas Pipelines, shall apply.

1926.351(c)(3)

When a structure or pipeline is employed as a ground return circuit, it shall be determined that the required electrical contact exists at all joints. The generation of an arc, sparks, or heat at any point shall cause rejection of the structures as a ground circuit.

1926.351(c)(4)

When a structure or pipeline is continuously employed as a ground return circuit, all joints shall be bonded, and periodic inspections shall be conducted to ensure that no condition of electrolysis or fire hazard exists by virtue of such use.

1926.351(c)(5)

The frames of all arc welding and cutting machines shall be grounded either through a third wire in the cable containing the circuit conductor or through a separate wire which is grounded at the source of the current. Grounding circuits, other than by means of the structure, shall be checked to ensure that the circuit between the ground and the grounded power conductor has resistance low enough to permit sufficient current to flow to cause the fuse or circuit breaker to interrupt the current.

1926.351(c)(6)

All ground connections shall be inspected to ensure that they are mechanically strong and electrically adequate for the required current.

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  • thanks for the detailed answer. I used a welder as an example, but in reality, it's to run a high-end computer server, electrical only, no gas. Sorry I should have been more specific in my initial description
    – Azulith
    Commented Jun 30, 2022 at 20:40
  • Good to know because it being a welder kinda changes everything ;) and I was about to edit your title.
    – Mazura
    Commented Jun 30, 2022 at 20:44
  • lol @Mazura, ok so then should I be connecting ground from the new subpanel to the ground piece in the old one? Not to the neutral bar, correct?
    – Azulith
    Commented Jun 30, 2022 at 20:52
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    @Azulith - Ed says yes. (?) Not sure why he doesn't like your EMT as a ground tho. Also, I take it back anyway, a 40 amp $100k computer gets a ground wire, fullstop.
    – Mazura
    Commented Jun 30, 2022 at 21:07
  • ground wire meaning from the old subpanel to the main? The new subpanel with the circuit will have hot/hot/ground (no neutral, 240v only), which will go back to the ol subpanel into the breaker (hot-breaker/hot-breaker/ground-ground bar). The old subpanel pictured seems should be grounded through the conduit to the pain panel. Are you suggesting I should run an additional ground wire from the old subpanel to the main, or what I've listed in this comment should be sufficient?
    – Azulith
    Commented Jun 30, 2022 at 21:40

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