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New 30 Amp Shed Sub Panel underground electrical feed. - Should I use 10/3 UF-B or 10/2 UF-B and is

Post in 'DIY and General non-hearth advice' started by Don2222, Nov 26, 2011.

  1. Don2222

    Don2222 Minister of Fire

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    Hello

    I got a 2 circuit 30 amp sub panel at Home Depot for $13 dollars. Now the wire is where they get ya!!

    Here is the same box for $29.00!
    https://solarconduit.com/shop/square-d-qo-load-center-2-circuit-30-amp-surface-mount-indoor.html

    Well, It is a nice weekend to teach my son trench digging 101 with a pick and shovel! LOL

    The dirt next to our foundation I thought was concrete it was so very hard!!

    So I showed my son what a pick ax is used for!!

    Anyway, what wire should I use and how deep do I go? 1.5 to 3 feet? How to attach a ground rod?

    I need about 150 feet since the main panel is on the opposite end for our house!

    Attached Files:

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  2. Morgan

    Morgan Member

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    If you want 120volt circuits then you need 10/3 wire...........10/2 and you could only have 240v circuits as you have no neutral wire. I don't think you need a ground rod......however I am not an electrician so I could be wrong
    on that. I would go about 2' deep and put caution tape at 1' deep, not sure if its code, but a good idea.
  3. Don2222

    Don2222 Minister of Fire

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    Hi Morgan

    One of my friends used 12-2 romex and put a plug on the end and plugged it into one of his house outlets. Then in the shed he just dasy chained a few outlets and then to a light. LOL But it has been working for 10 years!!
  4. Hass

    Hass Minister of Fire

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    I usually see people go between 2-3' deep, and put the wire inside of PVC. your main panel should have a ground rod on it (and/or be grounded to your water main), so there should be no need for you to use another ground rod.
    I assume you're not using permits then, correct?
  5. Don2222

    Don2222 Minister of Fire

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    Yes, my main panel is grounded to the main water pipe. Quite a few years ago I had an electrician check the ground and put a new connector on it so I know that ground is good! I did get a permit for the shed and the shed was approved in the final inspection. No electrical permit. So if I do the electrical correctly I should be all set.
  6. begreen

    begreen Mooderator Staff Member

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    Just the opposite. 10/3 will give you two hots and a neutral. That will give you the option of having 240 and 120V in the shed. But if this is overkill and all you plan on needing is a lighting + convenience outlet or two, then 10/2 is sufficient for a single 30 amp, 120V feed, though given the distance I would fuse it with a 20 amp breaker in the shed to allow for line loss. You don't need a ground rod, but it wouldn't hurt. Not sure what depth is required for your locale, but I'd go at least 24".
  7. bluedogz

    bluedogz Minister of Fire

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    When I did exactly the same thing, I used 10/3 to a subpanel in the barn, and hired a local rent-a-drunk to dig a 36" trench to hold the conduit. Probably overkill, but I banged an 8' ground rod in outside the wall where the subpanel is mounted- overkill till the barn was struck by lightning a year later, and went straight down to the ground rod with no damage!

    This allowed me to have a 240v receptacle in the event I need one, plus plenty of outlets and lights all over the 28x278 barn.
  8. Don2222

    Don2222 Minister of Fire

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    Thanks BeGreen for setting us straight. 18" rang a bell in my mind! Ding Ding!! LOL

    One more burning question for you BeGreen

    If I wire with 10/2 for 120v then how would I wire the top two feed terminals?? Would they be jumpered together??
    Actually it seems to me that you are suggesting using one 20 amp breaker and leaving the other slot blank which makes sense?
    See pic below

    Attached Files:

  9. Don2222

    Don2222 Minister of Fire

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    Cool bluedogz.

    How many amps is the sub panel? How many circuits?
  10. begreen

    begreen Mooderator Staff Member

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    Yes, you are correct. But I don't know what the loads are going to be in the shed. If there will be multiple heavy loads running simultaneously, then running the 10/3, 240v feed would make more sense for the two circuits. But if just lighting and a few outlets then running them off a single 20 amp breaker is fine.
  11. Hunderliggur

    Hunderliggur Minister of Fire

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    Rules of thumb: 15A 14 GA, 20A 12 GA, 30A 10GA.
    SINGLE point of ground in a residential system at the main electrical panel.
    If you want/need lightning protection there are specific ways to do this other than grounding the sub panel.

    I am installing 450 feet of underground power on my farm right now. 10-3 is so much fun to work with! For longer runs, upsize the wire gauge: 20A > 100 Feet = 10 GA instead of 12.

    And I would run two circuits using the 10-3: a 30A 240 breaker in the main panel and 2 x 20A 120V breakers in the subpanel.
  12. jamierah

    jamierah Member

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    I'd run the 10/3 it gives you twice the available power for a little extra cost. Install a 30amp 220v breaker in the house and then put 15 or 20amp breakers in the shed. If you go 24" deep you don't need a conduit but it might be worth thinking about burying a 1.5" or larger conduit so if you change your mind later you can pull a bigger wire and upgrade your service without digging a new trench. No ground rod is necessary if you have a ground wire running back to the ground in the main panel.

    150' rent a trencher for your back's sake.
  13. nate379

    nate379 Guest

    Subpanel is going to need ground rod. Might need 2 of them depending on local code... most places do require 2 now a days. Also need ground from main to subpanel.... so for a 240v run you need the 2 hots, 1 neutral and 1 ground. 120v the same minus 1 hot.

    I could pull out the book and tell you where it says it but I don't have it with me.
  14. Don2222

    Don2222 Minister of Fire

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    Thanks again BeGreen

    I think I will go for the 10/3 UF-B and 2 15 amp breakers in the sub panel since the sub panel buss is rated for 30a and connect that into a 30 amp breaker on the main panel. This way I will have enough for almost any load.
  15. Morgan

    Morgan Member

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    Yea I wasn't thinking about just sending 120 out there, most sub panels I am used to have provisions for 2 hots and 1 Neutral and Earth ground, giving you the choice of 120 or 240. If it was me I would run 10/3 just in case I had a need for 220/240 in the future. Compressors, welders and electric heat would all be reasons for 10/3 to be ran now and have to over with.
  16. davmor

    davmor Member

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    This is the way I did my 100 amp subpanel in my barn. Better to be safe than sorry.
  17. smoke show

    smoke show Guest

    I'd like to see some pics of said 150' hand dug trench.
  18. jharkin

    jharkin Minister of Fire

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    + 1

    This is a VERY important point. Ask any professional electrician for confirmation.


    Never never never bond neutral and ground anywhere else then at the service entrance. If you bond it in the sub neutral current can flow back to the main via the bare ground wire. If you have bad luck and have a loose connection of that ground upstream you can end up with a hot ground. Very dangerous.

    Did I mention don't ever bond hte ground in a subpanel?
  19. nate379

    nate379 Guest

    No less hand dug in the middle of winter?! At this point of the year I'd probably just put the wire over the top of the snow and not mess with it till the ground thawed out... or rent a backhoe/mini excavator at least!

    OP, you better be buying your son some beer and steak dinners!


    Oh for the question on the ground rod, put in the 2 rods and connect with copper wire. Usually you use a smaller wire than the main running in, but being it's just #10 wire for the main, you probably don't want to go smaller.


    You still haven't said what you are powering in there.
  20. begreen

    begreen Mooderator Staff Member

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    As long as you wire the the 2 circuits with #12 wire in the shed you can use 20 amp breakers. I would recommend this if you are going to be running multiple loads like a 12" saw and shop vac for example. The load calc is not split ( 30amps / 2.) Actually each 120v leg has the potential to carry 30 amps. The current alternates between the two legs 60 times per second.
  21. oldspark

    oldspark Guest

    Yes that is correct, other wise you could fry the the wires if there is a problem and the ground is back at the main panel, thats why there is supposed to be a ground rod at the sub panel especially when it it 150 feet from the other panel, some good info in this post and some so not, hope you can sort it out.
  22. oldspark

    oldspark Guest

    Make sure you do your voltage drop calculations for that long of run.
  23. Hass

    Hass Minister of Fire

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    holy smokes, tons of contradicting info here.

    my question is, why no electrical permit?
    If you got one for the shed, why not for the electric? Electric requires a permit 95% of the time when doing new work. In some areas around me, homeowners aren't even allowed to pull permits and do it themselves... You need a licensed electrician to pull the permit and perform the work. Easiest way to get the correct answers would be call up the inspector and he could tell you in a few minutes.
  24. oldspark

    oldspark Guest

    I agree Hass but some bad info from you, you have to have a ground rod at the sub panel. The wire in a conduit is a good idea, then down the road you can up grade or pull new wire if there is a problem.
  25. Hass

    Hass Minister of Fire

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    Like I said, if he would call the local inspector (or electrical inspectors if they are different from his town inspector) all of this could be solved easily and to the code per his area.

    There are variables, lots of them if there should be a ground rod driven in or not.
    Typically you don't ever ground the neutral in a sub panel. For a DIYer to figure out what to ground and what not, that might be a bit tricky.

    and you can actually just fish the wire back through PVC if you're feeling adventurous. Put a piece of cable or something on the one end... Pull the old wire all the way out. Attach new wire to the cable that you just pulled through when you removed the old wire... Then pull the wire cable back through. If there's not a lot of bends it's usually pretty easy. Just gotta make sure you attach it really good.

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