I'm just starting a job, and in the spec it states to come out of a slab with PVC-coated galvanized rigid conduit, but from there I have to use rigid aluminum conduit. Is it okay to connect the two different metals together? The spec also says to keep the aluminum isolated from other metals with plastic sleeves or plastic-coated hangers. What are your thoughts?
This is a really great question. Plastic sleeves or plastic-coated hangers are common isolation options to prevent corrosion from dissimilar metals. Another option, according to Article 344.14 of the NEC, is to use galvanized couplings to make this transition where not subject to severe corrosive influences. We also recommend using a thread compound such as STL8 at the joints where dissimilar metals are present.