How to run extra power to attached garage?

Question

I have an attached 3 stall garage. It only has one 20amp breaker running all the outlets. One of the stalls I use as a small wood shop and I need more power.

I’m thinking about adding a 100 amp sub panel next to my main to run power to the garage. My main concern is that I have to run my new outlets with conduit and I’m unsure about how to get them out to the garage walls.

I was thinking about running a single large conduit to and LB to the garage wall. Then from that LB to a box the run 3/4 conduit to outlets. There would be 4 12/2 romex cables running through.

Is this possible to do? Should I do it differently?

For reference, this is what I'm trying to accomplish:

This is where I'm hung up as to how to accomplish my goal:

Answer 1

To add a few things to George's excellent answer:

I would simply place the sub-panel in the shop

This is a key. Because the garage is attached, you can run each circuit as a home run back to the subpanel-next-to-main-panel. But putting the subpanel in the garage has some real advantages:

• Feeder from main panel to subpanel can be aluminum. Large size aluminum wires for a feeder will almost certainly be less expensive than several small size copper wires for individual circuits.
• Any time you have breaker trips and any time you want to work on add or change circuits it will be much more convenient with the subpanel in the garage than in the main house.

If you actually want a subpanel next to the main panel because you need more circuits for the rest of the house, add two subpanels - one in the house and one in the garage. Panels are actually pretty cheap - you can get a 20 space (that's spaces, not "circuits") for $100 or less.

Also keep in mind that the wire size has to match the feed breaker. You could have a 42 space subpanel with a 200A breaker if you get a good deal on one. But if you only need 90A (which happens to fit with some good aluminum wire prices) and you use a 90A breaker in the main panel then you don't need to use expensive 200A-capable feeder.

Most importantly, for any circuit (feeder or branch), pick either cable or conduit with individual wires. Never use cable with conduit - it costs more (you're paying for the cable sheath and for the conduit) and running cable through conduit requires larger conduit than the equivalent individual wires require.

Answer 2

Great question! When I wired my woodshop (large), I used Wiremold 4000 series Raceways. I knew that woodshops/workshops are always evolving so I wanted a flexible system that I could add/remove/move circuits as time passed. They are about a 4" wide raceway with covers that you can just pop off to run a new circuit. Outlets fit into a part that snaps into to raceway. Super flexible. Yes, it will cost more initially, but it can future proof your shop.

Next: I would simply place the sub-panel in the shop and directly connect it to the raceway. That would also serve as a ground. Run a main feed to the subpanel in the shop and get a big panel, breaker space is cheap compared to having to replace a too-small sub later. And of course the sub needs a 4 wire feed: 2 hots, a neutral and a ground and the neutral and ground must not be bonded (IE: neutrals go on the neutral bus bar and grounds go on the grounding bus bar. You may not even need grounds if everything is hard piped with metal or, if you go the raceway route directly connected to the sub-panel.

Answer 3

Just adding one point re placement of the panel, in response to your note about the water.

The code requirements are about space around the panel and are not specific to water pipes. You need 30" of horizontal space along the wall the panel is in / on, from the floor to 6-1/2' up, free of obstructions. The panel does not need to be centered in that 30" space. You also need 36" clear in front of the panel, and the panel door has to open to at least 90 degrees.

The diagram below gives a picture of the required clearances. It looks to me like your location may not meet these requirements given the white pipe or column to the left, what looks like a wood post to the right, and a small object I can't identify at the very bottom of the photo -- but I also can't tell dimensions from the picture.

I agree with everyone else about all the other parts, especially putting the panel in the garage. That has numerous advantages, as noted.

(I'm still new here so someone please let me know if this should have been a comment instead of an answer -- thanks.)