I recently bought a home built in 2007. I had the chance to meet with the original homeowner who shown me some of the things that were on his list to finish before he sold the house but never got the chance. One of the things was the completion of a 100 amp subpanel in an outbuilding I will use as a shop. Eventually I will add another 40 amp subpanel that will come off the 100 amp subpanel in the shop, to go to a nearby barn in the future.

What he has set up already is a 100 amp double pole circuit breaker in the main panel. I had no idea where it terminated at until he shown me a J box on the back of the house, which it was not tied into yet, but it was in the wall. It just needed to be brought out, so I did. I tested it to make sure the breaker operated that cable. All good so far.

The shop has a wire ran in ground that can handle the load also. It was coiled in the crawlspace, so I brought it out through the wall. The pic I have below is the pair I brought out. enter image description here What I am looking for in the picture is what type of weatherproof low profile box is out there that I can use to tie these into, preferably not using "bugs" that will take a ton of tape and what ever else is used to keep the cables from shorting out.

The cable from the breaker is going to enter the Jbox from the top, the one feeding the shop is going to exit out of the bottom.

Maybe it is expecting too much, but if there is a box that will recess into a 2X6 wall and leave room for insulation behind it and had enough cubic inches to handle the cable with out sticking out too far would be pretty cool. I imagine if there is such a thing, knowing the name of the Jbox would prove handy. I really want to stay away from a trough.

The next pic is of the subpanel itself. It has 3 lugs. I am figuring with the right name and a hopeful edit of my pic, that the ground wire can be sorted out too. enter image description here I figure, but I would like confirmation, that the new lug for the ground can be screwed or bolted to the back of the box and tie it in there. The biggest cables are 1/0, I can't remember the size of the ground wire...

Then again, I may need to get a different panel for the shop, and use this for the future barn. I hope this one works, only because it will save a trip.

Thanks guys.

  • You're going to need ground rod(s) at the outbuilding (or some other accepted form of grounding electrode). Did the previous owner have one installed? – Tester101 May 10 '15 at 11:54
  • You should be able to pick up a grounding bar at the local big box, hardware store, or electrical supply shop. I would suggest going to a local electrical supply shop, as they should be able to get you all the products you need. – Tester101 May 10 '15 at 11:58
  • Nope there is no grounding rod there yet. THAT would have slipped my mind. Thanks for the reminder. I kinda figured it is a matter of adding a bus bar. I also had a DUH moment too, I could pop open the main panel in the house and inspect how the connections are made in that panel, albeit perhaps a bit different, since the outbuilding is just a subpanel. – Jack May 10 '15 at 15:26
  • As far as the ungrounded (hot) terminals, it doesn't matter which goes where. They could both be black conductors, it wouldn't matter. – Tester101 May 10 '15 at 17:12

First thing I would do it get a larger sub-panel. Those dinky 6/12 panels are terrible for space and future expansion. You also need a means of disconnect at the outbuilding. I would get a 20 space main breaker panel which would correct both of these issues.

In the sub-panel you would also need to install a grounding bar to the back of the panel box and NOT install the bonding screw. The green wire would terminate there as well as the required grounding electrode (ground rod typically) conductor.

At the house you MUST protect that URD cable where it is exposed. Typically we'd use Sch80 PVC conduit. For the splice you can/should use Polaris connectors. They are available at any electrical supply house or even some home centers. They make larger aluminum wire splices a breeze!

There are a LOT of other code requirements for a job like this. Are you experienced enough to tackle this job?

  • Thanks Speedy, I knew I would get good feed back on the bunch of you guys, if I got you the right info. Yes I can handle it, it is pretty straight forward, it is needing to find out in a way of speaking "the right tools for the right job". In this case the right connectors and Jbox. Testor came through with the reminder about the ground rod, 2 spaced 6' apart, were required in MD that I can remember. The SER cable is not exposed anywhere. That link you posted is spot on, I have seen those on some of my jobs.. Need the grease.... well on any aluminum connection... Now the Jbox... – Jack May 10 '15 at 15:30
  • When connections are made in a Jbox, do I need to loop the cable in the box for expansion, or can the cable from above be connected straight onto the cable exiting the box straight on?. If I have to loop it, the Jbox would need to be something like a 16"x16", that would sure clutter up the outside of my patio. The original owner had a plastic 8"x8" surface mount, which he was going to drill the back the pull the cables through. That would have been a tough act to follow. The recessed box I know will make it easier to situate the cables inside. – Jack May 10 '15 at 15:37
  • Don't the breakers in the panel count as the disconnecting means, because there are only 6? – Tester101 May 10 '15 at 17:13
  • @Tester101, sure, they can, but that is a 6/12 panel. It's WAY too easy to exceed the six handle rule, and IMO it's foolish to install such a tiny panel with such a large feeder. – Speedy Petey May 10 '15 at 21:26
  • I was going by what the rating says it could handle. I guess I need to check out what the six handle rule is. With the 40A double pole breaker for the future barn, for the lights and few receptacles it may need, I was still able to have 4/8 circuits for the little 12'X24' shop. No plan for any 220 outlets. But I may just go with the bigger panel as suggested to go that way if I chose to later. You just never know... – Jack May 10 '15 at 23:22

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