Firecaulking is usually red, not always.
This is what you need to look for. It's available at HD in the caulk section, probably around $13 a tube.
A nailplate protects the cable/conduit from nails/screws that are installed during construction. You only need these if the cable or conduit is closer than 1.25" to the stud edge. If you are centered in the top/bottom plates and keep the cable in the middle of the stud, you won't need them. Nail plates are metal rectangles of various sizes (2x4 up to 2x12") with 4 bent- in "teeth" on the corners. Installing them is simple: hammer them into the studs/plates where (if) the cable is too close to the edge.
How do you know if a wall is fire rated? Look at the blueprints. I don't do a lot of residential work, but I would imagine that kitchen and exterior walls are fire rated on both sides, as well as the garage wall, and any wall that has a fireplace. Local building codes may also list other walls as needing to be fire rated. Those LV nail on plates only come with a 1/2" or 5/8" face, and can't legally be used in a double sheetrocked wall: the box face can't be recessed more than 1/4", and has to be flush with the finished wall if the wall surface is flammable (like wooden paneling).
I do hotel work where almost everything is fire rated, so I always use closed-back boxes. They are not much more expensive than open back ones, and are better not just for fire, but for reduced sound transmission.
The problem with 3" PVC in a 2x4 is that you have to completely cut away all the wood to get the conduit in. If the walls are not perfectly aligned, the conduit will wind up slightly outside of the stud bays, which will be a problem come drywall time. Cutting out the entire top/bottom plate is also not good from a structural standpoint, and I'd bet that it's against building code. 2 or 3 1.5" EMT conduits would present none of these problems. This is not a major change order.
The other problem with a 3" pipe is that, unless it is very full, you would need firestop
sticks to seal it. Great Stuff is a draft seal and, like all polyurethane foams, is highly flammable. It is not a firestop. Here's an
article on firestop.
Jack
