how did you do it? i'm doing something similar but permanent: running four AWG10 THHN wires (L1, L2, N, Gnd) from the panel located in the garage, via the crawlspace and crawlspace vents, to a backyard shed. I'm probably going to use liquidtight conduit around the vents and in the crawl. It's a flexible, easy to install conduit and comes in various diameters. 3/4inch is common. When running individual wires like i'm doing, conduit is a requirement here. Another benefit is that unlike say EMT rigid conduit, LiquidTight won't rust (we're in a salt-air environment). An other option would be to use up the solar conduit that I have too much of. It's not water tight at all, but provides mechanical protection to the wires. Anyone knows if that's a bad idea in a crawlspace?
Chris' answer above is nice and clean but I don't like the idea of drilling through the foundation. Ours is old and somewhat crumbly. I believe going through the vents with conduit will be to code, maybe not pretty at the vent, but to code. Thoughts? Thanks!