Can I run pvc conduit to aluminum junction box?

I am planning on mounting lights to the outside of my corregated metal garage. I had planned on using white aluminum wet location boxes that
have two mounting ears that screw directly to the metal and running pvc conduit (1/2 inch) throught the metal siding into the back of the box opening. I am hoping this gives the best weathertight seal.
Is it allowable to have pvc go into a metal box? Also, I planned on drilling the closest as I can the exact size hole of the conduit in the metal to eliminate a possible leak and using silicone. If I have to use a threaded fitting into the back of the housing, wont that size be impossible to duplicate? Is there a better way to do this?
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wrote:

It is legal to go that way, just be sure you run a ground wire and bond that box. There is a boss for a green ground screw in there and it usually comes with the box. What isn't legal is plastic boxes and metal raceways unless you use bonding bushings and bond the raceway. That is "hold your nose" legal.
The metal "Bell" boxes have threaded hubs so you use a male adapter on the raceway and thread it in. The easiest way is to assemble the threaded adapter into the box, mount it, then glue up the rest of the raceway to the box. I usually drill a drain hole in any box that is exposed to the weather. They all get water in them, either from small leaks or condensation.. Keep your splices toward the top of the box and point the wirenuts up. That mitigates nuisance tripping of the GFCI.
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Yes it's allowable by code, although you should ask your local inspector if PVC is allowed indoors in your local area. When PVC burns it emits a cyanide gas that can be lethal. Because of this, some places forbid it's use indoors except for service entrances or other short runs, such as nipples.
If you prefer to do the penetration with metal and no connector, you could install a threaded nipple from the outside bell box, through the corrugation and into a threaded LB on the inside. Then install a threaded connector into the other opening in the LB and run your PVC from there. As far as the size of the hole in the corrugation, don't make it tight. You're better off leaving it a bit large which will allow the silicone a place to settle into and cure. Silicone does shrink a tad, so you're much better off if you can get it to ooze through the hole and form a bead on both sides of the opening. On a final note, when you go to mount the box outside and make the penetration, make sure the top edge of the box is slightly below the high point of a corrugation/siding fold/bend. Then run a bead of silicone across the top and 3/4 of the way down both sides of the box. This will prevent water from getting in the top or sides while still allowing for drainage along the bottom just in case it does get in there.
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