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Advise on remodeling a shed into a shop

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  • Advise on remodeling a shed into a shop

    Hey guys. I have an old shed in the back yard, about 12x14 that has been just taking up space out there for a long time. Guy that built it left it with open rafters to the outside and it was nothing but a spider and tree-rat habitat. I have decided to get busy and make something useful out of it. I want to move most of the metal-working equipment out there and get out of my basement and garage.

    Last weekend I demolished all the squirrel crap infested shelves and hauled all the chewed up boxes and other garbage out. I also started adding a soffet around the roof to seal that up. I plan to insulate the interior and add some type of minimal climate control to it.

    My main concern is how to plan power for it. Right now I have a smallish bench mill 1HP and 10x22 lathe (about the same). Both are 110 devices. I also have a chop saw, drill press, grinder, shop vac, 20Gal Compressor, and belt sander. All are on the small side.

    I'd like to have a dedicated circuit to each of the mill and lathe with an option to go to 220 if I ever get something a bit bigger. Also a plug-in light or two would go along with each machine. Another 15A for the other workbench equipment and then possibly another 15A for main lighting so if a breaker blows I don't go pitch black although I will be adding windows to the building as well. Better still would be two 15A runs for bench as well as another one for the CNC computer and CAD/CAM workstation.

    Main issue is I don't think my house panel will support a sub panel with a 70A to 100A load to the building. I was thinking that given this is a one person operation that two machines plus lights would be the probable limit so 60A would be enough to get by but I hate to do that since it isn't much room to grow. Upgrading the house service for this adds a lot of up-front cost. The other option is to have the power company add service to the shed seperate. Easy then to setup for 125A service and have all kinds of headroom for power. My boss seems to think it's not a horrible charge or anyhting nor monthly rate as she does it on her detached garage that way and has no billing issues from it.

    Anyone have experaince with either scenario? I'm planning to do most of the wiring work inside myself, but I shy away from working on anything back beyond the breaker panel. Figured I would run it all on exterior cunduit so it always easy to reconfigure later with tearing things open again. If I upgrade the house I think I would need to go to 200A service to support a decent sized sub-panel and I have to trench at least 65 to 70 feet to get to the shed from the breaker panel in the house. I think if the power company adds a meter they take care of trenching from the transformer to the building as part of the fee.

  • #2
    Well, I don't know about anyone else, but unless you get a very large welder, I'd be very impressed that you can run enough to draw 100 amps in a 12 x 14 shop with some small hobby sized machines. I've got a similar setup with a 125 amp double breaker in my main panel however my shop is about 10x the size.

    Personally, I'd install a 60 amp double breaker to take 240v to a subpanel in your shed. Then run your 120v circuits from there. If you are concerned about future growth, you could put in a 100 or 125 amp subpanel in the shed and size the buried wire for the heavier load (use a voltage drop calculator to size the wiring, under 5% drop is code). Then, if you ever need the extra amps you swap out the 60 amp for a 100 or 125 amp breaker in the main panel and if needed, replace the main panel.

    Also, don't run the conduit from the outside directly into the main panel. Run it into the wall nearby and leave a loop in the wire before going into the panel. This way, if you do upgrade the main panel, the wire to the shed won't wind up being 2" too short to reach the new breakers and causing you to utter many bad words.

    Last edited by SteveF; 06-13-2012, 04:33 AM.


    • #3
      Check on the floor , how strong is it and is it above the level of the outside soil .
      Very important with machinery that you dont get wet feet.


      • #4
        All I can say is about 1979 my father retired sold out and we built a new
        40X50 shop a good 300 feet behind the house. I trenched it and we put
        phone, cable , another cable with lots of wires (for whatever) 3 strand alum
        (as thick as your index finger) for power all in pvc pipe. Now the house I
        would say its bearly 100 amps still has glass fuses, however it has 220 to
        the panel. I hooked it all up. Now this is June 2012 I run 1>220 IR 80 gal
        compressor, 220 AOSmith 225 amp welder, 220V SBend lathe,110V GK Heavy
        20" swing lathe, 110v Lincoln mig, 4) 110v grinders 3)110v drill press, 1) 220v
        very big heavy drill press, 1) 110v shaper, 110v chop saw, 110v power hack
        saw. As I write this i dont know how many flur. lights but enough, outside
        yard lights, and a share of band saws etc. I am a retired one man band,
        I can not run all these things at once. Only thing I can think of was heavy
        welding going on and the compressor started and pop a breaker. I fixed
        that I bought a gas Miller ac/dc I love it (its on the tool truck) never used
        the old Smith again. I say you are good to go. Till now I kick myself for not
        running a water line. Anyways I have no problems at all oh, 110v furnace.


        • #5
          Make sure the shed is where you would want a potentially bigger shop (future) and then I would go "big" in terms of electrical to the shed. Big enough so as to have the option in years to come of running a line back to the house [basically just do everything in reverse from what is most often done]


          • #6
            +1 on what SteveF stated on the electrical..... It's basically what I did for my shop and it has worked well.



            • #7
              My brother had to run power to a shed about 75-100 ft from his house. He had someone come with a machine that bored the hole underground. They dug a couple of holes about 18"x18" at either end and worked from there. I am not sure how deep they went though. It beat the hell out of trenching it. He only had to deal with refilling a couple of smallish holes.



              • #8
                I put in a separate supply to my workshop also. I made it a 200 amp so no way I'll be short whatever I do in the future.
                "Patriotism is the last refuge of a scoundrel"


                • #9
                  Originally posted by rowbare
                  I am not sure how deep they went though.
                  Minimum depth is 24" for buried wire and 18" if wire is in conduit.



                  • #10
                    Right now, I'd put in the biggest cables between the house and shop
                    that I could --- sized for the expected future load plus a good additional
                    margin. You can keep the current house service, meter, and panel
                    for now and then upgrade later, as funds are available and the need
                    presents itself.

                    The questions I'd have about separate service to the shop are whether
                    there is a minimum charge on the bill and what the local power company
                    will charge to install it.

                    Finally, if you (eventually) increase the house service and feed the
                    shop off of that, you gain the benefit of increased house service
                    (electric heat in the basement? a/c? etc? etc?) and you can trade off
                    load in the shop and the house.



                    • #11
                      I had a separate meter for my shop when I was in Iowa and it had a separate monthly bill. My tradeoff was the cost of copper for running a feed from the existing service vs. the extra monthly charges on the separate bill. I got double billed for all the extra charges: fees, regulation charges, etc., etc., etc. I was in a trailer park so I figured it was temporary and copper was at a high point at the time (post Katrina). So I just decided to pay the monthly charges. But if this is a permanent situation, you may want to sharpen your pencil before making the decision. You could easily be out many hundreds of dollars a year in future years.

                      In Florida I built an attached shop and the run was short to it so copper was cheap. I upgraded to 150 Amp service and added a sub panel in the shop. Worst cost was the copper from the pole. No problems with capacity ever.
                      Paul A.

                      Make it fit.
                      You can't win and there is a penalty for trying!


                      • #12
                        When I lived in Tennessee, eelctric co-op was able to pull the meter from the house, installed it on the pole to both shop and house. I had to trench in a 4" (I think) PVC counduit to the pole and blow a pull string through it. No extra per month since there was only one meter.


                        • #13
                          You're not likely to be running everything at once unless the other half is doing something too. I put in a 70A line with a 50A breaker going to my shop. (Couldn't find a 70A breaker at the time.) I run a big compressor, lights, machines, welders, grinders, fans and all but never once popped the main. But I rarely use them all at once.

                          I also have a drop from that line for my plating shed and a motorhome/outdoor outlet box. Both of those are set up with 30A breakers. If I ever do pop the main, I can always slip in a 70A breaker. The wiring is already setup for it.
                          Last edited by CCWKen; 06-13-2012, 03:02 PM.


                          • #14
                            I wouldnt bother having a seperate service installed. Your shop is tiny as it is, so why lose wall space with another panel? Use a breaker off your house panel.
                            "I am, and ever will be, a white-socks, pocket-protector, nerdy engineer -- born under the second law of thermodynamics, steeped in the steam tables, in love with free-body diagrams, transformed by Laplace, and propelled by compressible flow."


                            • #15
                              I was faced with the same problem and I ended up installing a new larger exterior service box on the house, from there ran an underground line to the shop, 200 amp service there. The house service remained as it was :100 amp. I talked with the power company and this route made the most sense for me, two meters or services entailed two bills, and both with a minimum charge. Upgrading the house entailed major changes and grief, so this solution gave me plenty of power to the shop at a reasonable cost.