I planning on adding a subpanel to my shed. I think I have done my homework and here is what I was planning. I was going to add double pole (40AMP 240 volt breaker) to my main panel. It is about an 80 foot run between my main panel and the subpanel I am adding. I already have schedule 80 PVC buried and I was planning on running THHN 8 gauge wire (4 wires, 2 hots, neutral, and a ground) between my main panel and my subpanel. On the subpanel (70A Homelite) I was planning on adding 2 x 20 AMP circuits and 1 x 15 AMP circuit. One of the 20 amp circuits would be for inside receptacles the other would be for outside receptacles. I was going to protect each of these circuits using a GFCI (first) outlet. The 15 amp circuit would be for lights (indoor and outdoor). I am going to use 12 gauge NOMEX NMB for inside outlets and 14 gauge ROMEX NMB for lighting. For outside receptacles I was going to use UF, USE, or URD and bury wire directly (I do not have PVC buried for this circuit yet). I was going to use 6 gauge bare copper wire between grounding bar in box and the 1/2" x 8' grounding bar. Even though there would be a potential for 55 AMPs to leave the subpanel, it will likely never exceed 20 or 30 AMPS.

I have the following questions:

1) with this plan would I be getting 120 volt 40 amp on each of the hot wires running between the main and sub or would it be 120 volt 20 amp on each of the hot wires?

2) I was going to buy supplies at home depot, is THHN best option for run between main and subpanel?

3) PVC broke near surface after it was installed. I have fixed this but there is some water inside. I have blown most of it out with a shop vac, but it remains damp inside. What can/should be done?

4) PVC currently has a 90 degree turn (second) and then comes out of ground about 3 feet from shed (in lawn). What would be best way to get PVC against shed? Top of 90 is near surface so I couldn't just add another 90 turn. Pull box would be ideal but I understand they can't be buried and would prefer not to leave it on surface.

5) Can bare wire ground be left exposed between box and grounding rod or can/should it be protected by PVC?

6) Is ROMEX NMB appropriate for inside shed? It is 20 x 10 new construction (very dry inside). If it is run inside studs I assume it would not need to be run inside PVC? Is Romex appropriate or would I need to use some type of wire that is rated for outdoor use? If so, what would you recommend?

Thanks,

Scott

I have the following questions:

My answers are in bold.

1) with this plan would I be getting 120 volt 40 amp on each of the hot wires running between the main and sub or would it be 120 volt 20 amp on each of the hot wires?

40 amps per leg no matter if you draw 120 volts or 240 volts.

2) I was going to buy supplies at home depot, is THHN best option for run between main and subpanel?

Be sure the wire is rated THHN/THWN, which is typical. I will explain in the next question.

3) PVC broke near surface after it was installed. I have fixed this but there is some water inside. I have blown most of it out with a shop vac, but it remains damp inside. What can/should be done?

Any wire pulled thru underground conduit must be rated for wet locations, since the chance of water in that conduit is very likely. So, THHN/THWN is rated for wet locations. Any insulation with a W in the code is for wet location.

4) PVC currently has a 90 degree turn (second) and then comes out of ground about 3 feet from shed (in lawn). What would be best way to get PVC against shed? Top of 90 is near surface so I couldn't just add another 90 turn. Pull box would be ideal but I understand they can't be buried and would prefer not to leave it on surface.

Is moving the shed an option? Sorry only kidding. Personally I think the best option is to dig up the sweep down the where the conduit is running horizontal, cut off the sweep, and continue the conduit to a new sweep to rise up where you desire. Any other method will be mickey mouse.


5) Can bare wire ground be left exposed between box and grounding rod or can/should it be protected by PVC?

Only need to sleeve the ground wire where exposed to physical damage. If you can bury it a few inches would be fine. If the wire is exposed on the surface of the shed, a conduit sleeve will help protect it, and probably look better.

6) Is ROMEX NMB appropriate for inside shed? It is 20 x 10 new construction (very dry inside). If it is run inside studs I assume it would not need to be run inside PVC? Is Romex appropriate or would I need to use some type of wire that is rated for outdoor use? If so, what would you recommend?

Providing it is just a work shed, and not will not have any livestock, NMB is fine. Just use common sense to run the cable where it will not get damaged, either behind a wall sheathing or up high as much as possible.

Scott,

1) With your plan you will be getting 40 amps on each leg at 120V.

2) The wire you suggested is fine; you may find THWN for #6.

3) Get what water you can out. Most PVC pipe leak overtime anyway.
In a year if you were to pull your wire out you would find it is wet.

4) If possible, the best way about this is to dig down to the 90 degree bend cut it off and extend your pipe run to the shed then 90 up where you want it.

If it isn’t possible to get to the 90, then it is possible to purchase a junction box (J-Box) that you will bury. These j-boxes have a lid that is screwed on to prevent anyone from gaining easy access to it. You will need to 90 up right next to your original pipe run and continue the new run to where ever you want it on the shed.
When you pull the wire from the main to the sub, pull the wire up into the j-box and back down to the shed without cutting it if possible. You should leave a little loop in the j-box also.

If you have to cut the wire at the j-box, you must use special Kearny’s or water proof wire connectors to prevent exposure to the elements. The other thing to worry about is your water table. You should provide some drain from j-box so water doesn’t fill up and short out your splice. That’s why I suggest not splicing in the j-box.

5) Any ground wire #4 or larger can be exposed. If you use #6 or smaller you are required to protect it with some type of chase (pipe, track). It may be worth the extra cost to just use #4 if it is a short distance from you panel to the ground rod.

6) Romex is fine. No need for pvc pipe or direct burial cable. However; if you don’t cover the interior of you walls with something (drywall or paneling), then you may not run any wires horizontally through the walls. Each run must leave the switch or receptacle box and go vertically to the top plate where it is allowable to run horizontally. This is due to people using the wire to hang things on just being more susceptible to damage. Make sure both the outside and inside receptacles are GFI protected. I wouldn’t protect the lights in case the GFI trips because you would be left in the dark.

Good Luck
Steve

Thank you for getting back to me with such helpful information! At Home Depot the only wire they had was rate THHN and not THWN. I am going to go back and reconfirm, but I was a bit confused since I have usually seen similar wire rated as THHN or THWN. Also from info on the web it appeared that it was the same, but I guess it isn't in all cases?

I was hoping to use the J-box as Steve mentioned, but I understand that isn't supposed to be buried and I didn't want to leave it sitting in lawn... actually I should have been a bit more clear and the conduit actually runs under the shed horizontally after about 2 feet there is a 90 and it then just comes up in middle of grass. Even digging out the PVC until where it would be flush with side of shed doesn't seem like there would be enough room to put in a 90 and still have it come up along side the shed. Also the PVC is now sitting is a perched water table (gravel on top of backed clay) so when I dig around it, it is underwater, making it very hard to work with.

Also I am not still completely clear on what the best wire to use for the outdoor receptacles. They are not all going to be on the shed, but rather along the edge of a concrete patio along a pool. All outlets would be at least 10 or more feet from the edge of the pool. It seems UF, USE etc would be good option for direct burial or could run conduit and something else.. what would the advantage of doing it either way be?

Thanks again!

Scott

I like PVC, and THHN/THWN.
You can easily modify or upgrade later, by using PVC. Romex, you are kind of stuck.
Schedule 80, hope it is 3/4 or better.
I would pull 2 -#6's, 1 -#8, and 1 -#10 for ground. 60 Amp Breaker. Panel can already handle it. Welder?

Most THHN is dual rated as THWN, but you must be sure. If not try to find XHHW.

OK, so it sounds like the conduit is already under the shed. You may need to undermine the trench to fit the sweep under the shed, this will only need a small amount f digging. Really try to do this without a junction box.

Since it seems your pulling new wire, you won't need splices in a junction box. If my suggestion just does not work, look for an in ground hand hole. These are boxes designed to be used as in ground junction or pull boxes, they have a sturdy cover that needs to be exposed at grade level, and most have no bottom. Conduits can either enter the side of the box, or rise up out of the dirt, and the wire is contained in the box. Landscapers use these for the lawn sprinkler systems, also use in parking lots for pole wiring.

For the outdoor outlets with the wiring on concrete, cable is not an option. Best to use all PVC conduit with the proper fittings, and boxes, again use THWN or XHHW wire. For short distances, you may use UF cable in the conduit, but I would not recommend it. Really tough to pull cable in conduit, and a pain to strip and splice at the boxes.

If the PVC conduit runs horizontally, be sure to strap often to support it well, and keep it looking decent, as the sun will cause it to droop.

Scott

I would do everything in my power to not use direct burial. It is just more apt to be damaged. If there is ever a fault it is a real pain to troubleshoot/ fix.
Conduit would be the way I would do it. Code requires the pipe to be minimum of 18 inches deep unless covered with concrete or such.

The conduit run to the shed should be direct.
Try to not have a j-box.

Get the pipe as close to the shed as possible.
If you are a couple inches away you can bend the pvc by warming it.
If you don't have a pipe blanket or such, you can use the exhaust pipe on your car.
Just stick the pipe in as far as you need to, run your car, leave it in until it becomes bendable, hold it up to the conduit coming out of the ground and bend the offset you need to get it to the wall of the shed. You don't have to use schedule 80 pvc either, it is OK to use schedule 40 pvc for this application. Schedule 40 is obviously thinner walled and easier to bend once you warm it.


Hope this helps
Steve

Lot of good info from above.
Don't know if mentioned above, I would core drill, or penetrate floor, dig out from under shed, and have conduit in the wall. I hate exposed conduit.
To have conduit exposed is accepted, widely used, easier, cheaper.
I would put in the wall. I understand water is a problem.
Outside recepticles would use PVC also. Recepticles on shed, I would do from inside shed,
With no exposed conduits, And boxes inside, with flush cover on the outside(bubble cover?), Cleaner look, May even be cheaper and easer, than running allong the outside of shed.
With trench, you might throw in 3/4 Pvc, for TV, Tel, Computer. Doesn't get cheaper or easier than now.