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Power supply to small shop
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Power supply to small shop

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Power supply to small shop
Residential Wiring - The Right Way!

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Thread: Power supply to small shop

  1. #1
    Join Date
    May 2013
    Posts
    1,445

    Default Power supply to small shop

    My son is wanting a permanent power source to his small shop. Only talking about one 220 and one 110 line. He lives a little ways from me. I went up once and found there was no space in his main box. I ran basically a temp drop cord with #12 romex that plugs into a reciprocal at the carport to a small fuse box with one 110 line. I think he has like 4 reciprocals in the shop. He wants at least one 220 for checking stoves, etc.

    I told him this was temporary and he needed to branch off his main box in the house to a smaller box then run the proper wires out to the shop and a ground rod for the shop. I think # 6 or #8 would underground wire will handle the what he needs. I had rather not do it as I feel someone with more experience should do it.
    He has a friend that is supposed to come over and, he intends to just tie in at the hvac unit outside the house. I don't like that. My thinking is what happens when he is using the 220 in the shop and the hvac compressor comes on. I am thinking the hvac has #10 romex going to it. Then add a little distance and voltage drop to the shop when that 220 is being used could cause problems even if he comes off the hvac connection with another makeup box with two or three circuits in it. They are still feeding off one #10 line coming from the main box in the house.

    Comments?

  2. #2
    Join Date
    Feb 2012
    Location
    Lala land, OH
    Posts
    225

    Default

    First he needs to take a close look at what all he does in the garage or could do in the future. It's much cheaper to install a slightly larger service now then to rip it out and upgrade it later. The things to look for are large air compressors (220V) and welders. Sounds like he is repairing appliances. Ask him if theres any chance he will need to power up more then 1 220V appliance at a time (such as testing a stove while running a dryer through a cycle). Any of these or future plans for one will require a larger garage service.

    If there's no chance of the above, he may be ok with a 60A service to the garage. I would install a 100A subpanel next to the main in the basement. Remove 2 120V circuits that are in breaker slots above/below each other (like slot 1 and 3, or 2 and 4) and feed them from the sub panel. This will make room for the 100A breaker to the sub panel. Run the garage circuit to the subpanel.

    You can also run 4 circuits to the subpanel to free up 2 220V slots for the sub panel and the garage circuit (run directly to the main panel) This is not really needed unless there's really large loads in the garage such as welders.

    The friend might have been wanting to replace the AC run with a larger circuit (100A) and replace the AC disconnect with a 100A panel that would feed the AC and the garage. This would put a larger box on the side of the house and would prevent an additional wire run through the house as well as a indoor sub panel, but the existing AC run would need replaced. This would also make any future indoor circuit additions more complicated. Using the AC circuit as it is now (even without the AC) is a bad idea.

    In the garage, I would have a separate circuit for lights.. He'll thank you when he trips the 120V breaker and is not in the dark hunting for the panel.

  3. #3
    Join Date
    May 2013
    Posts
    1,445

    Default

    The sub panel off the main is what I had in mind. Yes, I think it would mainly be for checking appliances. It is a very small shop and I doubt he will be checking more than one 220 at a time. That being said, he may very well be electric welding at some point also.
    I hear they did it and everything works. I said it may work now, but may cause problems at some point. I think the friend is an electrician, not sure about that. Hope he at least ran a bigger circuit to the ac then branched off to the shop.
    Thanks for the comment MrT.
    Been a while since I have been on the particular forum.
    PS I actually still need to change the box in my own shop. I only have a 60 amp fuse box right now in it. I have a 100 amp breaker box I need to install so I can add more rec's higher on the walls. When I rewired it years ago, I didn't think and left the rec's low to the ground. It has been a garage and small apt for wife's grandmother from time to time. If I had know then that I would be checking appliances, doing woodwork, and a few other things, I would have done it a little differently. Now, I would have to make room on the walls for the rec's it is so packed!

  4. #4
    Join Date
    Feb 2012
    Location
    Lala land, OH
    Posts
    225

    Default

    Unless its a little 110V wire welder, welders can really complicate things. They often specify on the nameplate a size of a circuit or a specific breaker size.
    If he is still going to run a new "correct" circuit out there, I would advise him to settle on what kind and size of welder he would want before doing this.

    If he leaves that circuit and goes to sell the house, a competent inspector may catch it and report it to a potential buyer. The buyer may ask that it be corrected in their contract or lower their offer on the house.

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