DIY subpanel install

Discussion in 'Electrical Forum discussion & Blog' started by J Eickholtz, Sep 16, 2018 at 3:09 PM.

  1. J Eickholtz

    J Eickholtz New Member

    Dorr, MI
    I'm new to the forum, hoping some knowledgeable guys can help me out. I'm pretty sure the only code I need to worry about is National Electric Code (NEC) and I have done the best research I can.

    Current situation:
    -100 Amp meter socket
    -100 Amp? panel for house.
    -30 amp breaker for garage, not sure the cable is big enough for that, but it's there.
    -Pretty sure the panel is overloaded and I don't think I have a Main breaker. Not sure how this got through, I guess codes were easier back in '69.

    -200 amp meter socket
    -100 amp panel for house
    -100 amp panel for garage (I want to weld @ 50 amps and have plenty of room for more)

    My current plan:
    -Power company has to install the new meter socket. If possible I will use the Siemens MC0408B1200T to eliminate my main panel. It is basically a meter socket that has spaces for large breakers.
    -If the power company uses their own socket, which I think they will, I'll use 4/0-4/0-4/0-2/0 Aluminum MHF wire to the main panel. Is there a better/cheaper wire I can use for this? Do I need a bare ground? The run will be pretty short; straight from the socket into the panel in the basement.
    -2 x 100 Amp breakers, 1 for each subpanel.
    -2-2-2-4 Aluminum Mobile Home Feeder (MHF) wire to each subpanel
    -House panel is now a subpanel.
    -2" metal conduit 6" under concrete from the house to the garage. I think I can go down to 1.5" conduit but I want some room just in case.
    -100 Amp subpanel in garage

    Running to the garage is a challenge. It's detached and there is nothing but concrete and HUGE trees between the 2. I plan to trench out the concrete and run metal conduit under the fresh patch. Do I need to go 4 inches or 6 inches below grade? Do I need Rigid Metal Conduit (RMC) or can I use Electrical Metal Tubing (EMT)? The MHF is safe underground if it's in conduit, right? I have to go all the way across the house (25+40=65ft) and then about 9-10ft underground to the garage.

    I have also thought about tunneling between the 2 buildings, starting from the basement and aiming for a 6"x30" patch of dirt next to the garage. Anyone ever tried something like this? I am concerned that there will be roots in there because the canopy from 2 trees intersects about where I need my conduit run.

    I could also exchange my main panel for a 200 Amp, then run my garage off that. Either way I have to buy a new 200 amp panel and a new 100 amp panel, but with my plan I don't have to re-wire every breaker in my house, and I can buy a 200 amp panel with le$$ breaker spaces.

    My last question is about inspection. Will they need to see the conduit before I cover it with concrete? What about after?
    Last edited: Sep 16, 2018 at 3:21 PM
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