In preparation for a new cabinet saw purchase, I need another 240V circuit in my shop. There is no space on the current (small) subpanel out there that was installed by the previous owner, and it’s also way undersized for a woodshop anyway, so I’m taking this opportunity to upgrade the service. I’m confident in my electrical abilities, but wanted to run a couple of things by you guys. The current panel is a small, 4 slot breaker fed through a 30amp double pole breaker from the main panel in the house. My garage is detached and has its own grounding rod. It is fed by three 10gauge wires via PVC conduit about 100 feet from the house (i.e., no ground wire, just two hots and a neutral). My plan is to upgrade to 60amp service on a 125amp subpanel that my father in law had left over from a previous job.
I have two questions:
This first one is more of an FYI for myself. The current panel is fed, once again, by three wires. I understand that this was allowed by the NEC until 2008. However, the neutral and ground bars are not bonded in the subpanel. This is incorrect, right? The neutral wire coming from the house is connected to the neutral bus in the subpanel, and the grounding wire coming from the garage’s grounding rod is connetced to the ground bar in the subpanel, but they are not bonded. My understanding was that NEC allowed the three wire feed as long as the neutral and ground bars were bonded in the subpanel Again, this question is just for my own education.
My second question is just whether my plan makes sense and is correct. Here it is:
- Pull four new wires to the garage. Three 6gauge conductors (2 hots, 1 neutral), and one 10gauge grounding wire that is connected to the ground bar in the main.
- Mount my new 125amp subpanel in the garage.
- Backfeed a 60amp, double pole main breaker in my subpanel using the 2 hots from the house (I have the hold down kit for the main breaker, and backfeeding is allowed on this panel).
- Connect the neutral wire from the house to the neutral bus in the subpanel.
- Connect the grounding wire from the house to the ground bar in the subpanel.
- Connect the grounding wire from the garage grounding rod to the ground bar in the subpanel.
- Break the bond between the neutral and ground bars in the subpanel.
Does this all make sense?
Thanks a lot in advance.