I am going to be upgrading a full, very small 6-space panel in my attached garage to a much larger (40+ space) panel soon. I will have a number of circuits to run from this panel to a planned addition, then I will take advantage of the additional spaces to start bringing other wiring in the house up to (modern) code. To get from the panel, which will be surface mounted, in the garage, I will need to run the cable down the wall then through hole(s) punched in the brick foundation and into the basement/crawlspace.
My plan is to run as many pieces of conduit as I can get out of the bottom of the panel, and of as large a diameter as possible during the panel install. Only a few cables will be run on day one, but I want to have as much space available as possible for when I do additional work in the future, and I don't want to break out the sledge and chisel any more often than necessary.
At this point, I do not have a panel picked out, so I don't know what size knockouts may be available, however, I will beg/buy/borrow whatever tools may be necessary to make as large a knockout as possible to give myself plenty of space for the future expansion.
Assuming I get/can make holes large enough for 2" PVC conduit, how many 12/2 NM-B cables can I run through each one?
- Yes, I know pulling NM through conduit is difficult. However, these will be a fairly short runs (under 36", I'd imagine) straight down, then around one 90° elbow and through a short straight piece through the wall and into the basement, so the pain will be minimal. Since I'm thinking PVC, I don't need any sort of nipple on the inside for protection from the conduit, correct?
- Yes, I know that individual THHN would be easier to pull, but that would mean I would need a collection of junction boxen just inside the basement in a space that is already very cramped and/or to continue runs in conduit to a place where I can put junction boxen, which I don't particularly want to do.
- I would be OK with going with metal conduit if I can get a larger number of cables into each one. PVC is easier (for a non-electrician without the proper tools), but I can cut steel pipe, I just don't have any threading tools, so non-threaded fittings would be easier/cheaper (fewer tools to invest in).
Note that I have checked a couple of on-line fill calculators, but they don't give NM-B as an option for cable type because the general recommendation is to not pull cable in conduit.