isolating commons and grounds in a square d panel

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Old 11-16-18, 05:45 PM
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isolating commons and grounds in a square d panel

I need to purchase a Square D QO sub panel as I already have many AFCI breakers.

I know the panel needs to have the commons and grounds isolated so am I correct in thinking I need to purchase a Main Lug panel. I need 54 spaces 200 amp panel to install in my attached garage. The main lug panel I am looking at on Amazon is the QO154L225PG, but in the pic it looks to me as if the commons and grounds are connected. Thank You
 

Last edited by bdawson; 11-16-18 at 06:11 PM.
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Old 11-16-18, 06:29 PM
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No such thing as a sub panels.. There are just panels. When used as sub panels you need to buy and add ground bars to make them work as a sub panels. That or if two neutrals turn one into a ground bar and isolate the other.
 
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Old 11-16-18, 06:56 PM
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You need 54 poles worth of breakers for the garage? How big is the service to support that kind of load? Has anyone done a demand load calculation?
 
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Old 11-16-18, 07:09 PM
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That panel you linked to has the provision for Plug-on neutral which means you must add separate ground bars as those neutral bars cannot be isolated to be used for ground. They must remain as neutral.
 

Last edited by PJmax; 11-17-18 at 04:41 PM.
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Old 11-17-18, 06:44 AM
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Originally Posted by PJmax View Post
That panel you linked to has the provision for Plug-on neutral which means you must add separate ground bars as those neutral bars cannot be isolated from ground. They must remain as neutral.
If what you are saying is correct then that panel cannot be used for a sub panel if the neutral bar cannot be isolated from the grounds. ???? I believe the panel comes with the neutral unbonded and there is a screw/bolt that is added to bond the neutral.
 

Last edited by pattenp; 11-17-18 at 07:06 AM.
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Old 11-17-18, 04:42 PM
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I corrected what I wrote. Those are dedicated neutral bars only.
 
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Old 11-17-18, 08:12 PM
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Square D panel has bumps on the back for add-on auxillary ground bars.
 
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Old 11-18-18, 06:55 AM
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You just get one (or more) ground bar kits. The ground wire from your main panel goes to this, then all your grounds terminate here.



Your other question:
am I correct in thinking I need to purchase a Main Lug panel
Whether you use a main lug panel or a main disconnect panel depends on whether your garage is attached. You said it was, so MLO is perfect. No need for an additional disconnect.
But it may be worth pricing out a disconnect panel. Often times the packages (including some breakers) are cheaper than the MLO option. Either way will work in your case.
 
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