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Questions on rewiring power to the Garage

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  • Questions on rewiring power to the Garage

    I think I don't have enough power in the garage to run my 3650 + dust collector/shop vac.

    I found out (the hardway) that my garage power is connected to the same line as all the bathroom power sockets. I guess they did this so the garage power will be on a GFCI socket. (10 year old house) Tracing the line back to the breakout panel, I found the switch with a 15amp rating.


    1. Is this a simple job of replacing the breakout switch with a 30amp switch? Or should the wires be replaced?

    2. If it is not a simple job, I don't plan to do this myself...any guesstimates on how long a rewiring takes (hours or days?) so I don't get taken for a ride by the electrical contractor?


  • #2
    You cannot replace the breaker with one of a higher rating. Doing so not only violated the electrical code, but may cause a fire. Interesting little factoid, the National Electrical Code belongs to the National Fire Protection Association. I'm not sure a 30A 120v breaker is allowed for a circuit of this type, eight.

    Can't begin to guess the price. Location makes a huge difference. As does the amount of work that needs to be done. To keep bidders honest, ask more than one.



    • #3
      A 30 amp, 120V line would require 10 gauge wire and in my experience is not a common setup. For one thing, you get into the issue of higher voltage being more efficient than higher current for a given power rating. That's why bigger applicances will run on 240V. Do a search on the Woodworker's Corner for wiring and you'll find a bunch of info regarding 240V.

      If I were in your shoes and needed to have the wiring done, I'd put a 20amp, 240V line and another 20amp, 120V line into the garage with their own dedicated breakers and multiple outlets situated throughout the garage. If the electrician is already pulling wires, it shouldn't be that much more difficult or expensive to get both circuits put in place for very little extra cost in materials. Once that is done, run your big machines (only one at a time obviously) on the 240V outlets and the smaller ones on the 120V outlets. I don't think it matters much for the dust collector to be on 240V (since it doesn't experience heavy loading the way saws do), so it will also be on the 120V line. I think you'll be required to have a GFCI on the 120V line, since it's in a potentially damp area, but I'm not sure about the 240V line.

      Good luck and let us know how it turns out!


      • #4
        when you say 15A switch, i assume you mean the breaker in the electrical panel. you should NEVER use a breaker with a higher current rating than the wire. if you are going to be using your garage as a shop, i would suggest running a seperate feed from your existing panel to a sub-panel in the garage. this will give you all the power you need with room to grow. a good contractor should get the job done less than a day. but they charge about $55 an hour, and materials are cost plus 20%. so if you know someone with a little electrical background, it will save you a lot of money.


        • #5
          I don't know jack about electricity, except that it can really give you a jolt when you touch 2 wires at once!!! I can only tell you what my electician did for me:

          As mentioned by jrwoodchuck(I love these aliases), I had a 100 amp servise run from the main "box" to a sub panel at the garage. I've got power mammy including 2 seperate single outlet 240 lines to the AC/Heaters( I wish I had another one), 5 single outlet home run 120 lines, and at least 4 other multi outlet 120 curcuits. The 120 lines are all 12 gauge, and the 240 is 10 gauge. Better safe than sorry.

          Anyone know the max amperage rating of 12 gauge romex?
          keep makn\' sawdust!...just don\'t breath any.


          • #6
            Anyone know the max amperage rating of 12 gauge romex?

            Typically, 20 amps. Subject to modification by wild and wacky stuff, but that's the size used in most household 20a circuits.

            (anyone who disagrees with me may well be right. I am not an Electrician)


            • #7
              14 gauge: 15 amps
              12 gauge: 20 amps
              10 gauge: 30 amps


              • #8
                Thanks everyone! Appreciate your responses..

                (Jrwoodchuck: by 15A switch, I meant the "circuit breaker")

                THanks to the advice, I don't plan to do this myself. Even at 1 day for the rewiring, this is going to cost me as much as my 3612 I can't get this approved from da boss on the same month I got the 3612 sooooo, its going to be a while before I try. I'll let you guys know how it went!



                • #9
                  This is what I would do if I were you:

                  1) Remove the garage from the bathroom circuit.
                  2) Put in a 100 amp 220 breaker and run appropriate 600v rated wire to the shop and install a 100 amp breaker box.
                  3) From there, you break down the 100 amps into 120 and 240 circuits needed for your machinery, lights, etc.

                  While I doubt you will ever have everything running at one time, (in house and shop) you should not put undue load on either panel.

                  When I had a seperate service added for my shop, I worked a deal with the electric company. I wanted 200 amp service. I got 100 amp installed for free. I have a 200 amp box. At best, at any one time I'm only using 50 amps max. And that's with the compressor running (a 220 6hp vert. unit).

                  This may be something you want to look into. Electrical turned out not to be has hard as I thought it would be!
                  John E. Adams<br /><a href=\"\" target=\"_blank\"></a>


                  • #10
                    Thanks, John. Appreciate your suggestion. I'll take that up once my boss approves the budget

                    I found a temporary patch (heh, heh, my day job is software!) to the problem - I found that my garage door opener is on a separate 15amp circuit, so I am going to use that for the shop vac and the other 15amp for the tools.



                    • #11
                      Sounds like you found a Christmas present under the garage door opener.

                      Suggest that you reverse your choices - run a very heavy extension cord from the garage door opener outlet to your tools, and leave the vacuum and odd stuff on the bathroom circuit. Then when you want to secure your shop, disconnect or switch off the extension for the main tools. Less chance that you will dim the lights in the bathroom, or have an unpleasant surprise in the middle of a critical cut, when someone uses the hair dryer in the bathroom.


                      • #12
                        Extension cords are not a good idea. If you use one for the 3650: (i) it must be an AWG12 cord and (ii) it should be as short as possible (not over 25'). Even at that, you will suffer a voltage drop that is not good for your saw's motor.

                        You don't need 100 or 200 amps to the garage; 220V 30A to a small sub-panel is more than sufficient. This would give you 4 120V 15A circuits or 1 220V 15A and 2 120V 15A circuits.


                        • #13
                          On my 3612, an extension cord is necessary. The electrical cord that comes with the unit is so short that it barely clears the table, and I don't have a floor outlet in the middle of my garage.

                          With good quality plugs and sockets, and a sufficiently heavy cord, there is nothing wrong with extension cords. If you say "this is good enough" or use too long a cord, as often happens, then extensions are certainly bad.

                          I found a long heavy cord on sale at HD a while back. Too long, but nice and heavy. And far cheaper than the "wire by the foot." So I plan to replace the cord on my 3612 with one that is long enough to not require an extension - and at the same time, switch to 220. That will be a better solution, but in the meantime, I use an extension cord. A very heavy duty extension cord, that I put a standard metal box on with regular outlets, etc.


                          • #14
                            I have read that "extension cords not a good idea" a few times. But, logically I don't see the difference between running a 25 feet extension cord (proper gauge for the amps needed) and running 25 feet of wire to an outlet. It has to have the same effect right?

                            I did get a 50 feet extension cord (15amp) for the saw. I'll measure the voltage this weekend and let you guys know.



                            • #15
                              While the saw is off (no load on the cord) you will see full voltage. While the saw is running idle (just a few amps) you are not likely to be able to measure any voltage drop. But while you are cutting a heavy load, and the saw is working hard (full power) that is where you will see the drop. And while the saw is starting up, the load is so high you will wonder how the circuit carries it - but for only a fraction of a second. Your circuit breaker (and wiring) can handle a load FAR above the rating for a short period of time.

                              A simple test. Put a light bulb on the same extension cord as the saw. If it dims when the saw starts, you have a drop that you should worry about.