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I currently have a 200 A main panel outside my cabin. Inside is the main 200 A shutoff and on the bottom of the bar are 2- pass thru lugs. The panel is a Square D Model# hom816m200ftrb Panel has 8 spaces.

I would like to add a subpanel next to it that will be 200 A panel as well. The new subpanel would be Square D Model #HOM3060M200PRBVP. It will have 30 spaces

The reason for adding another panel is that the current main panel only has room for 8 breakers.

Is it ok to tie into those two lugs and bring the power into my new subpanel? Would I be better off going with a smaller subpanel and use a dual pole 100 amp breaker in my current panel? Any other suggestions or recommendations?

Please let me know if you need more details. I greatly appreciate it!

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That type of panel you have there is called a "ranch panel" or "trailer panel".

It is specifically designed to provide a few breaker spaces, and then carry the "full" 200 amps onward to another panel elsewhere. That's what the thru-lugs are all about on the bottom of it.

No one was ever meant to cram a whole house into 8 spaces, but we've seen it tried LOL by an electrandyman who didn't get the memo.

So yeah. Those lugs are absolutely for you to do that, and don't feel like you need to put it next to the main. Put it where you like, including indoors (that's better for the GFCI/AFCI breakers anyway).

If you want a few more than 8 breakers outdoors also, feel free to hang a subpanel off 2 of the 8 breaker spaces. That's what they're for.

The 8 spaces are also good for generator interlock, surge suppressor, solar for miles lol (if you plan solar, choose a main-breaker subpanel).

Also, don't be bashful about breaker spaces. Spaces are cheap, running out of spaces is expensive. Here's a 40 space panel for not more.

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That is fine. Connect the panels with 2" metal conduit and you don't need a ground wire between them, just 3 big wires 2/0 copper or 4/0 aluminum.

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  • Do you mind giving a little more detail about it being only 3 wires? My run to the sub panel will be about 7 feet. I was under the impressions I would run two hots off those lugs to the 200 amp breaker in sub panel. Then I would have a neutral on one bar and a separated ground wire in the sub panel and not use the (green) screw to tie the two bars together. Why would I not need the ground wire from main panel to suboanel. And if not how do I ground the suboanel? New ground rod and copper wire to it? Copper ground to existing ground pole that main panel is connected to?
    – Matthew S
    Commented Jun 5 at 18:26
  • There are two ground issues: Ground wire, ground rods. Ground wire is always required. It can either be an actual wire of a particular size (there is a table specifying it) or it can done using metal conduit instead of an actual wire. Using conduit as ground for a long buried distance has issues, in case the conduit ever rusts out or is damaged. But for 7' in a building that is not a concern. As far as ground rods, they are only needed when the subpanel is in a different building. You are correct about not tying ground to neutral in the subpanel.
    – manassehkatz-Moving 2 Codidact
    Commented Jun 5 at 18:34

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