Electrical – Is this plan for running a circuit in buried conduit correct

I'm planning on running a single circuit from my sub-panel in the garage to my backyard storage shed. This is an uninsulated, unheated wooden structure (pressure treated lumber, painted T1-11 siding, roof felt/asphalt shingle roof) for storage only – there will be no room for a workbench or tools or potting table or anything else. This is purely an extension of the attic/garage/junk-room storage areas.

I'd like confirmation that my plan is correct, and confirmation on a few details I'm not sure about.

The Load

• 4 – 8 plug in LED strip lights

  • each lamp: 1.1 amp, 60 watts
  • each lamp will be plugged into a NEMA 5-15 or 5-20 outlet at the ceiling (i.e. it will be very inconvenient to plug anything but another light into the other receptacle).
  • All lights controlled by a single switch just inside the door.

• 1 duplex outlet, NEMA 5-15 or 5-20

  • We're running the wiring so may as well put in an "accessible" outlet "just in case".
  • No planned usage beyond possibly running a small heater for short periods in the late-fall/early-spring.
  • If the potential draw over the proposed distances would be too great for any additional loads, I'll nix it.

The Code

• According to the Indiana Association of Building Officials, it looks like we're on NEC 2009 with some state amendments.
  • Welcome to Indiana, we're a decade behind. :/

The Plan

• Either a 15 amp or 20 amp GFCI breaker (yet to be determined)

  • I'm leaning toward 20 amp, so I won't be sorry later. WAF is high on this at the moment.

• 12 or 14 AWG THHN/THWN-2 wire (white, black, green) or 14/2 UF-B (which I already have, but may not have enough of)

  • 14 AWG and a 15 amp breaker or 12 AWG for either a 15 or 20 amp breaker
  • Assume from here that all wire is appropriate gauge for the breaker, I won't be specifying 12/14 at every mention

• Run NM-B from the breaker, through the garage to a junction box inside the building where the exit point will be.

  • Up to the rafters, across the structure and down to the exit point will be 50 feet maximum

• Terminate the NM-B in the JB (with a blank cover plate accessible inside) to feed through the outside wall of the house.

  • Wire nut to the THHN/THWN-2/UF-B in the box with standard "indoor" rated wire nuts

• Exit the building through a short stub of conduit directly into a pull hub on the outside to turn 90° down into the ground

  • The pull hub will be 12-18" above ground level.
  • Seal the hole in the vinyl siding with silicone caulk from the outside.
  • Seal the hole in the OSB sheathing with more silicone from the inside.

• Schedule 40 or 80 conduit vertically down, through a 90° elbow, horizontally about 20-25 feet and 12" or so below the surface, through a 90° elbow, then vertically up through the floor of the shed.

  • Backfill with the dirt that came out of the trench. I'm not worrying about gravel or drainage.

• Once the conduit is through the bottom plate of the wall, it will end and the wiring will run into a standard single-gang box where it will be pig-tailed to NM-B for the remainder of the inside wiring and to the "accessible" outlet using standard "indoor" wire nuts.

• I'll probably use metal "handy-box" type boxes with metal covers since they'll be mounted in the stud bays but exposed (i.e. not behind drywall).

  • I've got some push-in bushings for metal boxes, but will probably need more.

The Conduit Questions

• I'm sure it will be significant overkill for a single circuit, but for the minimal price differential, I'm looking at running 1" conduit. What's the minimum size conduit I can use?

  • This will ease pulling, especially if I've got enough UF on hand to make the run (I understand that pulling cable is much more difficult than pulling wire).
  • Buying and pulling the THHN would be more fun and make me feel professional, but justifying the cost may be a bit tough. (Hmmm… 50' rolls aren't that bad!)
  • This gives the capacity to easily pull another circuit to the shed should the need ever arise.

• Is standard Schedule 40 plumbing pipe acceptable as buried conduit or must I use the stuff in the electrical aisle of my favorite big-box store?

• What kind of fittings are necessary at the garage between the inside junction box and the conduit, and the conduit and pull hub outside?

• With only about 12-18" of conduit between the pull hub and where the conduit will disappear in the dirt, is 1 conduit clamp sufficient?

  • Do I even need a conduit clamp for that short a run?

• I presume, especially for burial, that the conduit should be glued together to keep water and dirt out. Do I use standard schedule 40 type plumbing primer and glue or is there something special for electrical use?

• Once inside the shed, do the wires need to be run in conduit between fixture boxes since they won't be covered by an inside finished wall?

  • i.e. the wiring will all be exposed. It will be neatly wire-stapled to the side of the studs.

• Is there anything glaringly obvious that I've missed?