I have an out-building 150+ feet from the main service panel with its own 240v 60 amp sub panel. It is powered via a four wire bundle going through underground conduit -- 2 x 120v feeders, 1 neutral, 1 ground. This is a sub panel in a detached building so the neutral and ground will not be bonded in the sub panel. The sub panel is on the inside of the building.

There is a Square D D222NRB non-fused 60 amp safety switch installed on the outside and that is what the underground conduit is connected to. The safety switch has two sets of two lugs for the incoming and outgoing feeders, plus a neutral bar to accommodate the in and out neutral.

Safety switch almost fully wired

There are no lugs nor any obvious spot to mount a separate grounding lug or bar for the ground, in the safety switch.

It feels wrong to not bond the ground wire to the safety switch box. I always bond the ground to the box in any metal enclosure I am connecting wire in. The lack of a ground lug and seeming complete lack of even a space to mount a ground lug is throwing me for a loop, though.

Is the ground wire intended to pass through the safety switch on its way to the sub panel?

  • 1
    What size are the ground and neutral wires? May 22, 2021 at 2:32
  • 2
    Do you realize that exterior disconnect is not required? The panel itself will suffice if there are <6 breaker throws, and if not, you can use a main-breaker panel. May 22, 2021 at 3:29
  • @NoSparksPlease - the wire is "mobile home feeder wire". Aluminum, 2-2-4-6. May 23, 2021 at 0:46
  • @Harper-ReinstateMonica - Yes, exterior panels are the norm in my area, so installing the panel on the inside and having a safety switch outside is definitely a notable extra step. I did think that an exterior shut-off of some sort is required by the NEC 2020 code for at least the service panel, so even though not necessary in my case (permit follows NEC 2017 code), it seemed like a nice addition. May 23, 2021 at 0:50

3 Answers 3


Look for the grounding symbol stamped into the switch enclosure

There will be a grounding symbol stamped into the switch's enclosure somewhere around the bottom-left corner, as per the wiring diagram. That symbol marks where the ground bar, a Square-D GTK03 in your case, goes -- there should be a hole and a bump near it.


As you suspect when line conductors are terminated or spliced in a box "A connection used for no other purpose shall be made between the metal box and the equipment grounding conductor..."(NEC 250.148(C)).

You could land the grounds on the ground bar and install the bonding screw. Then get a split bolt and rubber tape to pass-through the neutral.

Also you need at very least a chase nipple and bushing but probably a connector and raceway system for the penetration out of the back of the disconnect.


No problem.

The metal conduit connecting the subpanel to the disconnect switch will carry the grounding for you. You can simply terminate the ground in the subpanel and let the metal conduit carry it back.

From looking at the photo it appears you have not installed the metal conduit yet, you have individual THHN wires going through the bare knockout and through a hole in the building. You'll need to finish that up by installing the conduit I mentioned. I mean you could use PVC conduit if you really want to, but metal conduit solves the grounding problem.

As pictured it's two code violations: first individual wires not being in any kind of conduit, and second, no cable clamp exiting the box and presumably the same problem entering the subpanel.

  • I wish I had this advice when designing the system -- I definitely would have used metal conduit for the grounds. As-is, this shut-off switch connects directly to a PVC junction box, not the sub panel. May 23, 2021 at 0:51
  • I added a 1-1/2" conduit through the wall for the wires. What do you mean about needing cable clamps, though? I've never seen cable clamps used when conduit is in play -- only when individual romex wires exit the box? May 23, 2021 at 0:54
  • @Harper: Are you saying that individual wires inside the box should be in conduit? Isn't conduit used only outside of panel boxes?
    – ttonon
    May 27, 2021 at 22:01
  • @ttonon For some reason I was under the impression that several THHN or XHHW wires were just traveling between two boxes without being in any raceway at all. No, boxes provide the needed protection. May 28, 2021 at 4:10

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