I am installing a sub-panel into my garage for a shop, and will have 2 corners to traverse the thick, 2-2-2 125 amp feeder cable around to get to my service panel. These corners are made up of 2-3 ganged 2×4’s each. What is the best way to pass that cable through the corners, in order to continue routing it to my main service panel – creating a path using a forstner bit? coming out of the drywall(yet to be installed) at the corner with conduit? Going up and through the attic above it and back down (no corners but a lot more cabling)?
Also, does this cable need to be in conduit in the walls and/or attic?
Thanks.
Bull
Replies
I had this problem last week, if the cable are single conductor they must be in conduit, no way around it. But you can use SEU cable without conduit. Go through the attic , It be worth the extra cable. They make a romex in #2 cu. At a $ 1.05 a foot its not that bad.
Go by attic. Trying to feed your 4 wire #2 SEU around a corner of 3-1/3" framing can be difficult. I have seen it done but to prevent damage to the cable you need to bore some fairly large holes. Holes so large that IMHO they would likely weaken the structure. Also cables in walls tend to be much more subject to damage from nails or screws even when nail plates are used.
You are not required to use conduit unless single conductors are used. If it was a short run, under 50' or so I would be tempted to run conduit all the way and use individual conductors.
If I had to go with cable or it was a longer run I would install 2" PVC with a 90 in the attic and conduit down to each panel. Running the cable across the attic and stuffing it down the conduit. In this case a female adapter and a 2" romex connector added to the end of the pipe in the attic would make the powers around these parts happier. Protect the conduit with nail plates where it crosses framing in the wall.
The advantage to this system is that it provides good protection and allows for repairs or updates to be made without tearing the wall apart or damaging the cable during installation. It also makes adding circuit, within reason, easier by adding a box to either conduit run at a later date. If either panel is on an exterior wall and especially if there is a low slope roof adding the 90 and enough pipe to get the run into a more accessable area of the roof makes sense to me.
You will need to use 4 wire cable. Remember: neutral and ground are allowed to meet only at the point of first disconnect, your main panel. So, assuming that this sub panel will have a neutral and not be 240v only, you will need a seperate ground and isolated neutral. Most modern panels make this easy but check because some are easier than others.
Let us know how this project works out.