I live in the Dallas, TX area and have a 10' x 10' Tuff Shed that is located 3' from my house. I want to run electricity to the shed to power A) internal light (4-tube 4' fluorescent fixture at 120 watts) B) exterior light (LED 14 watt) C) exterior outlet (for casual use for hedge trimmer, weed eater, etc.). So let's call it 2-amps (rounding up a lot) with both lights on and say another 5 amps when I plug something "big" into that outlet. All together a max of about 7-amps.
The plan is to install a 20-amp breaker in the breaker box and run a single 12/2 UF-B cable from the breaker, thru the attic, out the soffit, down the exterior house wall, underground, up the shed wall and finally into the shed. The breaker box is on the other side of the house from the shed, so the length thru the attic will be about 65', plus maybe another 25' going up and down and around.
As the cable comes out of the house soffit (vertical), I will put it inside 3/4" schedule 80 PVC conduit to a 1-gang weatherproof box mounted on the side of the house which will have a 15-amp GFCI outlet rated WR/TR with an in-use cover.
From the external box, the PVC conduit will continue down into the ground 12" with a curving 90 to run the horizontal 3' to the shed, then another 90 curving bend up the exterior side of the shed to another weatherproof 1-gang box. This box will contain an exterior switch (for a cutoff) and the wires will finally run into the shed from the back of the exterior box.
Once inside the shed, I'll continue to use the UF-B 12/2 cable (exposed) to the 2 lights, 2 switches and WR/TR exterior outlet with in-use cover (I don't really need an interior outlet in the shed). I will run all the horizontal wire runs at the top of wall headers (to keep them out of the way) and come down vertical on a stud to the 2 switches, lights and outlet.
My questions about all of this are:
- Any problem running the 12/2 UF-B cable in schedule 80 PVC 12" below the ground? I think I could run THWN-2 wires in this conduit at 12", but I would rather use the UF-B cable I already have instead of buying THWN-2. Since it's such a short length with only 2 bends and the pipe is 3/4", I don't think I'll have too much trouble pulling the cable wires thru the conduit.
- Do I really need the cutoff switch on the shed? My understanding is that every remote structure requires its own cutoff switch at the structure. Even though I have a GFCI outlet on the house that is technically a "cutoff switch", it's on the house (3' feet away) and not the shed. And I think I understand the the GFCI is required BEFORE I go underground. Is a simple switch good enough, or should I get like an AC disconnect? And can the switch is on the exterior or should it be inside the shed as the first thing on the circuit? I could also put another GFCI outlet inside the shed as the "cutoff switch", but a switch would be cheaper/easier to install.
- Do I have to ground the shed with a grounding rod? The shed is sitting on concrete blocks and does not have a foundation, and I only have 1 20-amp circuit. So I don't think I need to do this.
- Do I have to protect the wiring inside the shed (with for example flexible metal conduit) or can I leave it exposed? I don't plan on covering the walls so the wiring will always be exposed. My "protection plan" is keep the horizontal runs high and the vertical on studs, all stapled, clamped at the boxes, etc.
- Should the GFCI outlet be 20 amps instead of 15 amps? The breaker in the breaker box will be 20 amps and I'm using 12/2 wire, so I really can do 20 amp outlets. On the other hand, I don't need anywhere near 20 amps for what I intend for this shed, and the wire run from the breaker box into the shed (after all is said and done) will be around maybe 90 feet, so my thought is to never allow a 20-amp device on this circuit. Is this reasonable thinking, or too conservative?
- Any input/comments to improve anything?