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ProGrade, Certified Electrical Contractor
Category: Electrical
Satisfied Customers: 514
Experience:  28+ years exp. - installation, troubleshooting, & repair of commercial, & residential electrical systems.
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I have a square d main plug on neutral ready I plan on using

Customer Question

I have a square d main plug on neutral ready I plan on using as a subpanel. I know I need to isolate the neutral and ground. I believe I need to purchase ground bus bars separately. Is this correct? Will I still be able to use the afci's without the pigtail? Also, do I need to isolate the neutral from the case? If so, how? I don't see a bonding screw. As for the main ground wire. What size do I need? It's 100amp sub and has 2/0 feed. Does it connect to the main panel? If so, what's the point of isolating the neutral from ground in the sub?
Submitted: 1 year ago.
Category: Electrical
Expert:  ProGrade replied 1 year ago.

Hi Brian, welcome to

Allen sub-panels that have a neutral load have to be fed with 4-wires supply and neutral & ground isolated from each other at the sub-panel and neutral isolated from ground. This is a safety requirement. If sub is only fed with 3-wire ad the neutral developed a problem, all metal parts of the sub and all grounded metal from the sub would be hot.

Should be a #6 Copper

Customer: replied 1 year ago.
i understand it needs a 4 wire feed. My main question is more about the new subpanel that I'm installing. I'm moving the old sub to a different location so decided to use a new one. Since it's not by the main panel I purchased a main to use as a sub so I could cut off power at either location. Being that it's a plug on neutral panel I don't see where you can isolate the neutral and ground by removing a bonding strap or ground screw. Do I need to purchase the ground bus bars separately? The brand is a square d plug on neutral. It's a 200 amp panel but will be fed with a 100 amp breaker.
Expert:  ProGrade replied 1 year ago.

The plug on neutral speaks to the type of breaker only. You would use Square D breakers designed for use in plug on neutral panels, they do not have a pigtail, this helps clean up some of the clutter in the panel.

The main neutral lug & neutral bus work the same as all panels. A bonding screw is required to bond the neutral, without it, the neutral is isolated. You will need to purchase separate ground bar (s) for the ground wires. Does that clarify your concerns? Thanks Ken

Customer: replied 1 year ago.
Is there a screw that bonds the neutral to the case itself that needs to be removed? If the neutral is connected to the case, and I add ground bars, they won't be isolated. This plug on neutral ready box seems to be designed differently than the old style.
Expert:  ProGrade replied 1 year ago.

Shouldn't be anything to remove, the default is that it is not bonded. You would need to add/install the bonding screw if this was being used as a main panel.

Brian, I checked with my Square D Distributor, if you need this panel bonded you have to add a bonding screw/jumper. If you will install the ground bar (s) and keep neutrals & grounds separated you will be goid. Thanks Ken

Customer: replied 1 year ago.
Thanks Ken.....when I researched online a lot of people mentioned removing the bonding strap or screw to use as a subpanel. I didn't know if the panel I purchased was different being that it's a plug on neutral ready. Your answer was exactly what I was looking for. One more quick question. The old subpanel has a separate ground rod. With the new location of the new sub it would be easier to run a ground to the main. Can I attach that to the ground bar inside the main or does it have to have it's own ground rod as to keep it from being part of the neutral/ground circuit.
Expert:  ProGrade replied 1 year ago.

Glad to help. If the new sub-panel is in the same building a separate ground rod is not required, if it serves a detached building such as a garage or shop, the ground wire and a separate ground rod is required.

Customer: replied 1 year ago.
Does the ground wire feed from the subpanel connect directly to the ground did or can it be connected inside the main panel.
Expert:  ProGrade replied 1 year ago.

Into the main panel

Customer: replied 1 year ago.
Sorry but one more quick question. I just installed two ground bars. Do I need to run a jumper between the two or is the case basically the jumper.Thanks for all the great help!
Expert:  ProGrade replied 1 year ago.

No need for a jump right if at least two screws were used to mount them.

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