View Full Version : Questions about going to 200amp service

08-20-2007, 06:22 AM
I am going to be building a garage addition in a couple months and have a couple questions regarding electrical service. My current service is 100amp (overhead), feeding into the side of my house where the garage addition is going to be built. I put in a work order w/ my power company and they came out and determined that Im w/in the allowable distance for them to run underground service at no charge to me (up to 200amp).

My question is whether it is possible to go with a 200amp panel in my new garage and connect my existing 100amp panel to it, essentially turning the 100amp panel into a sub-panel? If this scenario is doable, my plan is to run the conduit/wire under the garage slab to connect the two panels - Im doing this work on my own and want to do as much as the non-hot work as possible before having an electrician come out and make final connections. What type/size wire is used to connect the two panels? How about the conduit, 2, 2/5 or 3?

Thanks for any thoughts - Jeff

08-21-2007, 05:26 AM
In my own houses, I always put the main panel inside the garage and ran a feed from the meter socket, the meter socket had a main disconnect on or next to it. (I am paranoid about having a panel outdoors where anyone who wants to could turn off my breakers, and a padlock would just keep the honest people honest.)

08-21-2007, 01:54 PM
You can leave the 100 amp panel and make it a sub-panel if you want, or you can rip all that out and replace the 100a with a 200a panel, but, if you do convert that 100 amp panel, then you are going to have to separate all the grounds and neutrals and install a ground bar in the panel... and feed the subpanel with 4 wires...

08-21-2007, 06:56 PM
Upgrade your service to 200 amp.

08-22-2007, 09:03 AM
My plan is to upgrade to 200amp service when I build the garage and install the new panel - that is not in question. My question was whether it's doable to then make my existing 100amp into a SUB of the new main panel. From what Chris75 says, it sounds like that is definitely doable. I would have no desire to convert the old 100amp panel to 200amp if there is no need. I can't see a need if I'm going to have a brand new 200 amp main panel in the garage w/ a ton of open slots...does anyone else??

My only other question is what type/size of wire to run from my 200amp main to my 100amp sub? Chris75 - you may have answered this...did you mean to say "...if you don't convert that 100 amp..."??

Thanks - Jeff

08-22-2007, 01:19 PM
I would definitely install the 200 Amp service on the bigger of the two buildings, for obvious reasons... In your case I'm assuming it will be the House, then I would run 2" pvc to the garage for the subpanel, I would probably pull #1 AL. for the sub-panel feeder... This is just generic because I can't actually see your situation. and all situations are different ;)

Bob NH
08-24-2007, 08:12 PM
You can feed a 100 Amp subpanel with #3 copper. You will need a #4 copper neutral and probably a #8 ground (I don't have my code available for a few days to be sure of size).

You could get a piece of #2 Aluminum SE R and run a 90 Amp circuit for the subpanel and wouldn't need conduit. You could probably get #1 Aluminum SE R and run 100+ Amps.