[metagami]

My winter project is to build a 12x20 shed in the far corner of the back yard. I'd like to run electric service for lights and power tools. On the outside of the house about 30' from the main panel I have a 240V pullout switch that at one time supplied an AC compressor (since relocated to the other side of the house). It's connected to two 30A breakers in the main panel. The electrician who did the AC work said the switch would be a fine starting point to run service to the shed, which will be 65' from the pullout switch. So here are my questions:

1. Given the total distance, what's the correct wire size? I'm guessing 8-3, but would 6-3 be better?

2. The wire will run underground across the back yard. Is there a special rating or designation for wire that will be buried about a foot deep?

3. Do I need to run conduit from the switch down the wall and into the ground? I would probably want to do that even if it isn't actually required.

4. The shed will sit on a slab. I'll install conduit when the slab is poured so the wire can enter below ground then come up inside the wall. Can the conduit be cut off flush with the slab, or does it need to run all the way up to the subpanel?

5. Should I connect the subpanel ground bar to the ground wire coming from the main panel, or should I install a ground rod outside the shed and connect to that instead? I think the ground rod may be required. In that case, do I connect the ground wire coming from the main panel to anything at all? I understand the neutral bar must not be bonded to the subpanel ground.

6. Should the subpanel have its own main breakers, or should the incoming supply simply connect directly to the buss bars?

7. The receptacles will all be 20A using 12-2. Should (or must) they have GFCI? If so, is it better to use a GFCI breaker, or just use a GFCI receptacle as the first one in the circuit, with the other receptacles connected to the first? Is there a limit to the number of receptacles that can be connected "downstream" from a GFCI receptacle?

8. Is there a maximum number of receptacles allowed on a single 20A circuit?

9. I'm not planning on finishing the inside walls, so the studs and all the wiring will be exposed. Can I still use Romex, or is armored cable required? If the walls were going to finished, I'd just drill holes through the center of each stud and run Romex straight from box to box. In this case, though, that seems like it would create a hazard. Perhaps the wire should drop straight down along each stud from the ceiling?

10. Since I know I'm not going to be finishing the walls, should I still mount the boxes so they stick out 1/2" from the studs, or just mount them flush with the studs?

11. My plans call for ten 120V/20A receptacles, two 240V/30A receptacles, two interior fluorescent lights, and two exterior incandescent lights. In practice, at most the lights and a single power tool would ever be in use simultaneously. Are the two 30A breakers enough, or should I figure out some way to upgrade to 50A from the main panel?

Thanks for any advice you can offer!

Tim

[tkrussell]

Whew, OK here goes:

#1. Use THWN or XHHW copper wire for individual wires pulled through conduit, or UF cable if direct burial cable. See #11 for the size wire.

#2. A foot deep? If using PVC conduit must be a min of 18" deep, if using direct burial cable must be a min of 24 " deep. Only steel or aluminum rigid conduit is allowed 12 " deep. Dont even think of pulling UF cable thru small conduit.The smallest conduit for UF cable may be 1-1/4", and used as a sleeve, leaving the cable exposed at the point of rise, which is not allowed if the cable is subjected to any physical damage.

All buried conduit and cable must have a warning tape run the entire length of the buried run, tape buried 12" below grade.

#3. If using conduit with individual wires, the conduit needs to be a complete system, with the proper fittings, connectors, couplings, etc. end to end, box to box.

#4. See #3

#5. No ground rod is needed (and should not be installed) as long as an green equipment ground wire is pulled,(recommended and standard practice). The green wire connects to the equipment ground bar in the panel, which is bolted to the panel backbox. The neutral remains isolated on the neutral bar. Be sure the neutral bar is not connected to the panel backbox.

#6. The breaker at the main panel is sufficient, only need a Main Lug only subpanel, no main is needed in the subpanel. You can have one if you desire.

#7.The outlets in the shed will be considered as being outdoors, and GFI protection is required. Use either the breaker or receptacle, none is better than the other. No limit to downstream devices.

#8.No maximum outlets on a residential circuit.The guideline of max of ten is from the commercial code. However, the more outlets on a circuit the more chance of more outlets being used, esp for power tools, and more chance of an overloaded circuit.

#9. Running the cable up at the top horizontally on the surface is fine, then drop down in the bays as you described. Just be sure to protect the Romex cable from any physical damage. If there is any chance of damage then metal cable, or PVC conduit is required.

#10. Flush mount the outlet boxes is fine if there is no finish material.

#11. If you only use a 30 amp feeder, nothing else can be used without chancing tripping the 30 amp breaker if any one of the two 30 amp outlets in the shed are used.

I recommend using a 50 Amp breaker in the main panel and installing 3-#6 ( two blacks and one white) and 1#8 green equipment ground wire, in 1" PVC conduit buried 18" deep, or 1" steel or aluminum conduit 12" deep.

Anything less will prove to be a disappointment.

Hope this helps.