Square D Q0 200A Panel - how to convert to sub panel (separate neutral / ground bars)

pclausen · Sep 2, 2015

Appreciate the feedback. I removed the bond in the transfer switch between neutral and ground. I also realized I had made an error in the meter base. The ground to Panel A does not come from the meter base, rather it comes directly from the ground rods. Above pic has been updated to reflect.

By removing the ground to neutral bond in the transfer switch, the only bond that exists for sub Panel B is in the meter base. I was under the impression that the bond should always exists in the first service panel, which for Panel B would be the transfer switch, no?

Panel A is a service panel and ground is bonded to neutral within it.

Panel B is a sub panel being serviced be the transfer switch, so should a bond not exists there between ground and neutral?

hr3 · Sep 3, 2015

The only infraction I can see is your main service disconnect .. You can group up to six disconnects in a row and it was ok to do. Now your 400a service has one switch inside and the other outside ???

pclausen · Sep 3, 2015

Hmm, it would suck if the inspector makes me move the NEMA 3R transfer switch cabinet inside.

dstig1 · Sep 5, 2015

I would connect the ground from Panel B to the ground from Panel A. You get there in a round about manner through the transfer switch, but I would be looking to see it ground to the main system ground of Panel A. Might be small potatoes, but the way I would do it. Otherwise, it all looks logical to me. Bit of a complex system you got there...

pclausen · Sep 9, 2015

Regarding the main service disconnects, the transfer switch is service rated, so it must have a main disconnect. Since both inside panels also have disconnects (meaning I have 2 disconnects in a row inside), I believe that makes it ok. I just have double disconnects on the panel being feed from the transfer switch.

Dave, the original wiring had both panels grounded directly from the grounding rod. But based on the transfer switch installation manual, introducing the service rated transfer switch, makes is the service entrance and the location where neutral and ground must be bonded and any sub-panels feed from it, must be done so via 4 wires (L1, L2, N and GND).

I cleaned up the wiring in the transfer switch some:

Closeup showing neutral bonded to ground using the built-in strap.

And the ground coming in from the grounding rod(s) and also being feed to the sub panel.

Inside, I redid the grounds in the right side panel and got the covers on the conduit boxes. Left panel is all original and neutrals and ground are all bonded together.

I picked up a single long ground bar and mounted it at the top of the panel, thus eliminating the need to use wire nuts on all the ground wires.

Close up. I also used anti oxidation paste on the aluminum ground wires this time.

Finally, a shot from the outside again, showing the conduit box where the hole was drilled to reach the inside for the feeder wires. Can a conduit box be below grade?

I used a regular split bolt clamp to extend the ground wire from the grounding rod to the transfer switch. I believe the NEC calls for this to be a single wire with no splits in it. My understanding is the only way around this is to use irreversible crimps, but after pricing the crimp too for this, I think I'll be digging up the ground rod(s) and installing a new wire directly from it, all the way into the transfer switch.

hr3 · Sep 9, 2015

Article 230 says the will be grouped.. in other words side by side.. You now have one inside and one outside .. Your inspector probably won't even know the difference but if he reads the inspector news he might... ?
https://books.google.com/books?id=j...ge&q=more than one service disconnect&f=false