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Thread: Help with wiring house to garage to pole barn

  1. #1
    Join Date
    Sep 2018
    Posts
    4

    Default Help with wiring house to garage to pole barn

    Hello people, looking for some confirmation and or direction to wire from house to detached garage and pole barn from main panel in house. So my situation is I have a 200 amp service in my house and would like to pull 100 amps to my detached garage and then to my pole barn I only have 3 spaces left in my service panel. at first I was thinking pulling 3 #2 THNN and a bare copper #4 ground to the garage and use either a feed thru panel or just install a 100 amp breaker in that sub panel and then on to the Pole barn, however in order to avoid having to run conduit (1 1/4)under a 12 foot wide driveway I was wondering if I could pull 100 amps from main panel to a sub panel in the crawl space and from there use breakers to pull separate 100 amp wires to each garage and pole barn. Thoughts ? is it legal to use a sub panel in this manner ?

  2. #2
    Join Date
    Feb 2012
    Location
    Kent, WA
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    240

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    Depends on the crawl space. Is this space really a short basement, or is it truly a crawl space with a dirt floor where you'll be on your hands and knees? If its the latter, it may be a legal location for a panel but it is a crappy choice. Why not just put a new panel next to your main panel and put two 100A breakers in it (fed from a 100A breaker in the main panel)? Then, run those two 100A feeders through your crawl space and send one to the garage and the other to the pole building.

    Do you really need 100A in each location? It is difficult to use that much power. Things would be cheaper and easier if each feeder was 60A (or maybe 50A to garage and 100A to pole building). Have you done a load calc for either area?
    Mark
    Kent, WA

  3. #3
    Join Date
    Sep 2018
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    Thanks for the reply Mark, so the details of my site are as follows: the wall with my existing panel is an outside bedroom wall that is spray foamed insulated so adding a sub next to it would require removing drywall from the wall and digging out foam, the rim joist is very close to the first joist at the floor. making running wires very difficult there. When I built the house I installed a piece of conduit from the panel into the attic and another in a interior wall from the attic into the crawl for future runs. The crawl space is 4 feet high from a plastic covered dirt floor. As for the 100 amp service I always figured if you are going to spend the time and money to run a circuit might as well spend the little extra and put in capacity that you or a future buyer might want.

  4. #4
    Join Date
    Feb 2012
    Location
    Welland Ontario
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    422

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    4 feet high is not high enough for a panel. You need at least 6 feet of head room so you can stand in front of the panel.
    Operation Overlord.

  5. #5
    Join Date
    Sep 2018
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    I see, are there junction boxes that would allow me to splice inside ? perhaps one with lugs to split 1 circuit into 2 ? in that case I would consider a 60 amp #4 wires

  6. #6
    Join Date
    Feb 2012
    Location
    Kent, WA
    Posts
    240

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    Can you merge one circuit in your panel to another one to free up another slot so you have your 4 slots you need? If not, you can put a double pole breaker in the main panel and run it to a junction box in the crawl space where you split it to two different destinations. I'd use all the same size wire in this case if that's your plan (either 60A or 100A).

    When wires are #4 or larger, box sizing is based on conduit size and not wire size. If it comes in 1 side and out the opposite wall, then you need a box whose wall to wall length is 8X that conduit size (e.g. 8 x 1.25 is 10"). If there are multiple conduits, that can cause an increase in size. I would look for a 12x12x4 junction box to use for this splice. I'd use either two split bolt connectors on each wire or a split bolt and a butt type splice that uses set screws. The splice hardware available at Home Depot will be bare metal, and I've never seen the insulated Y type or multi splice hardware there. So after you make up your splice, you need to wrap it with rubber splicing tape (4 lapped wraps) and then cover that with vinyl electrical tape (2 lapped wraps). Basically, the tape needs to end up 1.5x as thick as the insulation you took off.

    For the ground wires, install a 5 hole ground bar in the splice box and put the 3 grounds on it (one incoming and 2 outgoing).
    Mark
    Kent, WA

  7. #7
    Join Date
    Sep 2018
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    First off thank you to all that replied, so after trying to make my original plan that I had laid out years ago work I decided to take a step back and take a fresh look and I think I have a better solution. Since my house service panel is mounted to an outside wall I will remove a knockout on the back of the panel and go thru the wall with conduit to the outside trench to barn, garage etc. My question now is since I have a 200 amp main panel can I pull 100 amps to the barn and 60 amps to the garage from the main panel (install 2 new breakers in my main panel) or should I run 100 amps to the barn install a sub panel and then install a 60 amp breaker from barn to the garage ? just not sure if adding a 100 and 60 amp breaker to my main panel is ok ? that would be the most economical and trouble free way to run if I can.

  8. #8
    Join Date
    Feb 2012
    Location
    Kent, WA
    Posts
    240

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    Ultimately, the load on your main panel will most likely be the same, whether it is from the garage or the barn. Yes, it is possible to overload the main panel if the barn pulls 100 and the garage pulls 60, but if you do a load calc that shouldn't happen. And if it does, the 200A main will trip anyway.

    So I would run this whatever way is easiest and works best for you -- two separate feeders, or feed from one building to the next.

    You'll probably need an LB fitting to transition from the back of the panel down to the dirt. Don't skimp on conduit size. I'd use at least 1.5" for 100A and 1" for 60A. Pulling is easier and the LB boxes are larger so easier to feed into them.
    Mark
    Kent, WA

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