Last fall, while running a roto-tiller in my back yard, I hit and damaged the 14-2 UF cable that was supplying my detached garage with lights (and 3 outlets). The cable was only buried about 6-10 inches deep—not very deep, and, as far as I know, shallower than any code ever allowed for direct burial UF cable.
Without knowing much, and wanting to get the lights back on as quickly as possible before winter hit, I rented a 30-inch trencher, and ran a 12-3 (plus ground) UF cable, and an 8-3 (plus ground) UF cable between the house and the garage. The run is about 100-110 feet long.
So what I have running to the garage now is a 12-3, an 8-3, and no ground rod. The 12-3 is temporarily standing in as a replacement for the cable I cut with the tiller (red wire not being used), and the 8-3 is not connected to anything.
I thought I could run a small 40-amp sub-panel off the 8-3 after I upgrade the over-filled panel in my house, and later use the 12-3 for a 3-way switch for an exterior garage light.
I know now that to “do it right,” I would have planned for a 50-60 amp sub-panel (if not more), with a 6-3 UF (if not larger), not 8-3. I was in a hurry just to get the existing garage circuit back on, and didn’t research what should have gone in before the trench was closed. So I have two plans to fix it. What would you do?
Plan A, assuming I drive a ground rod, can I run a 40 amp sub panel off the 8-3? Is there such a thing as a 40 amp subpanel? Is 8-ga just too small to be acceptable as a subpanel feeder? All I was planning on was 2-3 15-20 amp circuits for lighting and outlets, and 30 amps at 240 for a compressor, or possibly a heater.
Or, plan B, I forget the 3-way switch, use the 12-3 to run a shared neutral MWBC to two lighting/outlet circuits, and use the 8-3 for a single 240 volt outlet, up to 40 amps, and run it all off of the (upgraded) main panel in the house?
Plan B seems better now, because I could theoretically run a total of 80 amps if I’ve read the charts correctly (20 on each hot in the 12-3, and 40 in the 8-3).
If I use plan B, would I need a local disconnect for the 240 volt outlet in the garage? Is it acceptable to run a 120-volt MWBC to a detached building? Should I still drive a ground rod even if it all runs off the main panel in the house? If I told you that I threw a RG6 coax (TV) cable and 3 runs of CAT5 down there while the trench was open, would it change the grounding requirements? (Should I put another grounding block on the coax by the garage?)
(Plan C is retrenching, but I don’t want to think about that.)
Thanks for your input,
Joe “TheGonagle”
Without knowing much, and wanting to get the lights back on as quickly as possible before winter hit, I rented a 30-inch trencher, and ran a 12-3 (plus ground) UF cable, and an 8-3 (plus ground) UF cable between the house and the garage. The run is about 100-110 feet long.
So what I have running to the garage now is a 12-3, an 8-3, and no ground rod. The 12-3 is temporarily standing in as a replacement for the cable I cut with the tiller (red wire not being used), and the 8-3 is not connected to anything.
I thought I could run a small 40-amp sub-panel off the 8-3 after I upgrade the over-filled panel in my house, and later use the 12-3 for a 3-way switch for an exterior garage light.
I know now that to “do it right,” I would have planned for a 50-60 amp sub-panel (if not more), with a 6-3 UF (if not larger), not 8-3. I was in a hurry just to get the existing garage circuit back on, and didn’t research what should have gone in before the trench was closed. So I have two plans to fix it. What would you do?
Plan A, assuming I drive a ground rod, can I run a 40 amp sub panel off the 8-3? Is there such a thing as a 40 amp subpanel? Is 8-ga just too small to be acceptable as a subpanel feeder? All I was planning on was 2-3 15-20 amp circuits for lighting and outlets, and 30 amps at 240 for a compressor, or possibly a heater.
Or, plan B, I forget the 3-way switch, use the 12-3 to run a shared neutral MWBC to two lighting/outlet circuits, and use the 8-3 for a single 240 volt outlet, up to 40 amps, and run it all off of the (upgraded) main panel in the house?
Plan B seems better now, because I could theoretically run a total of 80 amps if I’ve read the charts correctly (20 on each hot in the 12-3, and 40 in the 8-3).
If I use plan B, would I need a local disconnect for the 240 volt outlet in the garage? Is it acceptable to run a 120-volt MWBC to a detached building? Should I still drive a ground rod even if it all runs off the main panel in the house? If I told you that I threw a RG6 coax (TV) cable and 3 runs of CAT5 down there while the trench was open, would it change the grounding requirements? (Should I put another grounding block on the coax by the garage?)
(Plan C is retrenching, but I don’t want to think about that.)
Thanks for your input,
Joe “TheGonagle”