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red86yota 12-02-2008 04:54 PM

add subpanel or replace main panel...
Hi, I'm working on a home addition, and will need a few more circuits than my current 100A 20-20 will allow for. The panel is completely full now, and tandem breakers aren't available for my GE box.

My question is this...are there any advantages/disadvantages over installing a subpanel for the new circuits versus just replacing the main box to a 32 circuit panel?

thanks in advance.

scatkins 12-02-2008 06:20 PM

Just went through this myself. Same situation - out of spaces. However my main panel was a 45 year old zinsco. (Which is pretty much a firetrap), so the decision to replace was a bit easier.

1) Depending on your installation of panel it can be a real bear to physically replace (i.e. embedded in stucco on exterior of house vs surface mount in a basement).

2) Since the new main panel is larger (and maybe different) you could have problems with the length of the branch circuit inputs (i.e. too short) which would require a bunch of splicing. But if you pick the right panel are careful you might get away without any splices.

3) Assuming existing main panel is in good servicable condition and you don't plan on upgrading service to 200A, It is really an easy decision to simply add a subpanel right next to the main and be done with it.

3) If you have any ideas that you might need to upgrade your service, then the problem is a little different. If you plan to do that, then add a new Main panel for it and then make your existing main a sub-panel (observing of course only bonding the actual main panel).


GuitarPlayer 12-04-2008 09:31 AM

What is the square footage of your new addition, combined with the square footage of your existing home?

J. V. 12-04-2008 09:43 AM

First of all. To install a sub panel you need two blank spaces in your existing main service panel. If your panel is full, where will you get your sub panel circuit from? Or you can move one 2 pole circuit to the sub to free 2 up in the main.
The size of your house does not always determine the size of the main service.
My recommendation is an upgrade to 200 amp main service. Then you can install a sub for convenience if you like. Think about the future.

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