MOB
New User
- Location
- California
- Occupation
- Engineer
I want to add more electrical power/circuits to my garage. My house is all electric with the water heater and clothes dryer already in the garage, and my wife wants an EV soon, so I see an upgrade in my future for the EV charger.
The garage is attached to the main house and is about 20' from the main panel. The main is full. The garage currently has 3 FMC conduits from the main panel (2 are 1/2" (with 30A/240V and 2x 20A/120V) and 1 is 3/4" (30A/240)).
I see two options.
Option 1: Add 100A subpanel
I need to make hole in the ceiling drywall of the hallway connecting the garage and main house for another project, so I though this would be a good opportunity to at least pull the sub-panel feeder wire. The hallway has an insulated dropped ceiling, with a 6" gap between the 2x8 ceiling joist and the 2x4 for the drop ceiling framing.
If I understand the code correctly, 310.15(B)(7), the feeder can be either #4 Copper or #2 Al wire. (Wire size >= 83% of the rated load, so for 100A load x 83% = 83 A. #2 Copper has 85 A @ 75C and #2 Al has 90 A @75C). I would use 4-4-4-6 Copper SE wire. Unless the insulation in the hallway ceiling requires the 65C rating, and using 3-3-3-5 Copper SE wire.
Am I correct on the wire size and which one?
Because of the 6" gap between the ceiling joist and drop ceiling I don't think that I need to be concerned with wire damage, so can the wire be pulled bare (no conduit)? (In side the garage, the wire would be pulled through holes drilled into the 2x10 ceiling joists until it terminates in the sub-panel on the wall.)
Option 2: Re-purpose 3/4" FMC
Could I use the existing 3/4" FMC conduit and replace the current wires in it with #6 Copper THHN for a smaller 60 or 70 A panel to provide power to the water heater and dryer and general laundry outlet. (310.15(B)(7) does not apply since this would be for a panel less than 100A. What is the applicable code and what size sub-panel could I use?)
One of the other two 1/2" FMC would power the EV charger (30 or 40 A) and the other would not change (2x20A/120V).
(No drywall or significant changes to the main panel.)
Thanks.
The garage is attached to the main house and is about 20' from the main panel. The main is full. The garage currently has 3 FMC conduits from the main panel (2 are 1/2" (with 30A/240V and 2x 20A/120V) and 1 is 3/4" (30A/240)).
I see two options.
Option 1: Add 100A subpanel
I need to make hole in the ceiling drywall of the hallway connecting the garage and main house for another project, so I though this would be a good opportunity to at least pull the sub-panel feeder wire. The hallway has an insulated dropped ceiling, with a 6" gap between the 2x8 ceiling joist and the 2x4 for the drop ceiling framing.
If I understand the code correctly, 310.15(B)(7), the feeder can be either #4 Copper or #2 Al wire. (Wire size >= 83% of the rated load, so for 100A load x 83% = 83 A. #2 Copper has 85 A @ 75C and #2 Al has 90 A @75C). I would use 4-4-4-6 Copper SE wire. Unless the insulation in the hallway ceiling requires the 65C rating, and using 3-3-3-5 Copper SE wire.
Am I correct on the wire size and which one?
Because of the 6" gap between the ceiling joist and drop ceiling I don't think that I need to be concerned with wire damage, so can the wire be pulled bare (no conduit)? (In side the garage, the wire would be pulled through holes drilled into the 2x10 ceiling joists until it terminates in the sub-panel on the wall.)
Option 2: Re-purpose 3/4" FMC
Could I use the existing 3/4" FMC conduit and replace the current wires in it with #6 Copper THHN for a smaller 60 or 70 A panel to provide power to the water heater and dryer and general laundry outlet. (310.15(B)(7) does not apply since this would be for a panel less than 100A. What is the applicable code and what size sub-panel could I use?)
One of the other two 1/2" FMC would power the EV charger (30 or 40 A) and the other would not change (2x20A/120V).
(No drywall or significant changes to the main panel.)
Thanks.
