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A year and half ago I set up my sub panel around the back side of my home for pool equipment and further outlets and patio lighting/fans.

I set 3x #3 copper THHN in a 1.25 ENT in the ground from my main panel (new '08) approx 170 feet around the back of my home to the other side of my home for a new QO load center run by a 2 pole 80 amp breaker in my 200 amp panel.

I didn't find that I needed to run the ground from the sub to the service main,only that the sub needs its own ground and the bond screw in the sub is removed.

Now I'm seeing that I do NOT meet code by not having the sub ground connected to the service main.

What would be the best way to upgrade this oversight?

Can I connect and bury a ground wire (#4 copper) to my ground rod for my sub and run it in the ground, not in a conduit, around to the ground rod for service main? I know where the rod is located.

Or must I run that ground into the main service panel to connect to the ground bar in the main panel?

I did not use ENT, I used rigid PVC electrical conduit and fittings glued together buried 18 in down all the way around my house through the walls and into the service panel. I was thinking about ENT while typing and didn't catch that I used an 80 amp Eaton breaker in my 200 amp main service panel. The QO load center I put in is rated to 200 amp but I didn't need that much, but I intended on over sizing the feeder wire to be good on wire size. I don't need 100 amps on that sub right now so 80 should be fine. The 1.25 pipe has a number of turns in it so I can see challenges getting through it, and the 3 wires may be twisted at some point.

QUESTION: Would I need to pull out all three wires while pulling in a pull cord, then reset to pull the three and the ground after that?

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    Just to be sure it's not a typo, are the conductors in ENT (plastic) or EMT (metal) conduit?
    – PhilippNagel
    Jan 27, 2021 at 4:18
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    Yes typo, I used rigid electrical conduit not ENT, was thinking about ENT when was typing. Thank you.
    – Matt P
    Jan 27, 2021 at 12:44
  • @MattP when you say "rigid electrical conduit", do you mean rigid PVC conduit, or rigid metal conduit?
    – ThreePhaseEel
    Jan 27, 2021 at 12:45
  • I used Electrical rigid PVC conduit and fittings glued together buried 18 in down.
    – Matt P
    Jan 27, 2021 at 13:01

1 Answer 1

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Thankfully, fixing this is fairly simple

The good news is that pulling an 8AWG copper grounding conductor from the subpanel to the main panel should pose no trouble, as you have plenty of fill to spare in your conduit for that fourth wire. In particular, Schedule 80 PVC in that size is no issue at 320mm² of usable fill area, which is ample space compared to the mere 211.92mm² of fill your feeder will take up once you add the 8AWG grounding wire to it.

The bad news is that you'll want to pull the existing wires out, pulling a line in at the same time, then use that pull string to pull the new bundle through. (You should be able to reuse the existing conductors provided they're in decent shape, though.)

Other notes: that 80A breaker can be bumped up

Note that there's no reason to put this feeder on an 80A breaker; 3AWG copper wires with an 8AWG ground can handle 100A when landed on 75°C terminations, which modern distribution equipment will have, as a rule. So, you can swap that 80A breaker for a 100A breaker. (Square-D doesn't even make an 80A panel, by the way; they have some tiny "spa boxes" rated for 70A or less, but anything larger will have 100A or 125A busses on it.)

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  • Yes, pulling all out and a pull cord in, resetting with all 4 cables makes sense. I can't do it myself. I've never used a winch in the past, how difficult is this to manage?
    – Matt P
    Jan 27, 2021 at 13:11
  • The sub is a 200 amp load center (primary sub) but didn't need that much, intended on over sizing the feeder cables. The 80 amps is plenty more than needed now. I also have at least one other smaller QO sub panel (fed by a 30 amp breaker) out in my shed connected to this primary sub and again only put in a local ground rod and did not connect the ground to the primary sub. Intended a second sub panel (also fed by a 30 amp breaker) on my new patio but running into issues on where to put it, would like to put it. Would like to put it inside a wall cabinet on patio, not sure if that works??
    – Matt P
    Jan 27, 2021 at 13:20
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    Is the reason for pulling the 3 existing wires and rerunning all 4 together merely a matter of convenience (i.e. not many people have a 200' fish tape), or is there some sort of code requirement to do so? i.e. If I had a short, 50' run, could I reasonably pull the ground wire through without pulling all the other wiring? Just curious how generally applicable that particular bit of advice is vs specific to this situation.
    – FreeMan
    Jan 27, 2021 at 13:37
  • @FreeMan -- mostly practicality of the pull, trying to stuff new wires down a conduit with existing wires already in it is rather hard from all I've heard
    – ThreePhaseEel
    Jan 27, 2021 at 23:35
  • Thanks again! I'm not expecting any more major electrical work in my future, but knowledge never hurts. Especially knowledge that defies common sense, yet really makes your life easier in the long run.
    – FreeMan
    Jan 28, 2021 at 12:09

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