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replace 15 amp with 20 amp?

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  • replace 15 amp with 20 amp?

    i know i saw a thread about this somewhere but can't find it now.

    my shop-garage- has only one 15 amp breaker feeding it and i keep tripping it when i use my ts3650 w/shop vac. i have 3 overhead lights and a fan constantly running, and my ts and shop vac are on a craftsman 15amp auto switch.

    can i safely replace the 15 amp breaker with a 20 amp? is there anything i can do other than hiring an electrician to run another line to my shop?

    tia for any and all suggestions!


  • #2
    Depends on the wire gauge

    If the circuit has only a 15 amp capacity, it will short or burn out at the weakest point before the 20 amp breaker can trip, which would not be good.

    Our electical code calls for min 14 ga wire for 15 A and min 12 ga for 20 A.



    • #3

      I would start thinking about running a 120/240 Volt line to your garage and installing a sub pannel out there. Sooner or later you will need extra power and be glad you did it. As for changing from a 15 to a 20 Amp breaker for now, that depends on the gauge of wiring running to your garage. As stated by another member, do not change the breaker of you have 14 gauge wire. If you do have #12 then you can switch for a 20 Amp. breaker. The problem is that before long that won't be enough. It will require hiring an electricial contractor and some $$$, but I would really think about doing 60 Amp. 120/240 Volt service to your garage. I hope that doesn't mean having to upgrade your house electrical service too. If it does, you might think about going for 30 Amp. 120/240 service in the garage and again installing a sub panel (little breaker box) in the garage. About the only other good choice would be to think about a good quiet generator running outside the garage to supply power and using several heavy duty extension cords. This would be only until you get heavy service run to the garage.


      • #4

        You may also want to check with the Electrician Corner on this Forum, or with the following one at

        I was able to add a 60amp sub panel to my workshop (6 gauge supply line), with 20amp breakers supplying my recepticles (12 gauge wire), myself using their advice.



        • #5
          Yep, need larger wire before uping the breaker size.

          You mention a Craftsman auto switch? Is that the one that has two tools pluged into it and when one is turned on, the other tool is automatically started? If so, I have one too!! LOL I "thought" I had a problem with the motor on my 6X48 sander so I replaced the motor 2 days ago. Guess what.....still tripped the breaker (20amp!) every time I turned on the sander. Shop vac was plugged in the Craftsman switch. Come to find out, if I yanked the auto switch and went directly into the outlet, it works fine. You might try that. Mine apparently is slowly dying. Had it for maybe 6 or 7 years. Liked it but seems it's biting the dust. Staggering your startup load may do the trick.

          Congratulations to Mr. "the sky is falling" Al Gore, nominated the new Village Idiot!


          • #6
            I put a 100amp subpanel in my garage/shop. Even a panel that size will fill up in a hurry if you have a separate breaker for air compressor, welder, etc. Better to go a little larger than you think necessary at the time and have the capacity later. Not much more expensive to go to 100amp.


            • #7
              The reason you are popping the breaker all the time probably has to do with that switch. The starting current of all motors is much, much higher than the running current, even under load. If you will spin up one device and then the other in sequence, you may not have the problem any more.


              • #8
                While it's best to have a qualified electrician help you figure out your loads and needs, a one man shop rarely runs into problems with over loading.

                Personally, I have a 60 amp service to my shop. I have my 220/2hp air compressor AND my Jet, 220/5hp table saw on the same circuit.They run at the same times, sometimes. Never had that breaker trip. I have another 220 circuit for my 3hp shaper, 5hp drum sander and welder. BUT, I can only run one at a time and NOT when the saw is on, so the load never rises much. I also have dedicated 20 amp circuits run for my dual 3hp Porter Cable router table and one for my sander/shop vac/dust collector, but again, one guy can only have just so much on at any one time. I've never blown the main and only lately tripped the sander/shop breaker because of the Craftsman auto switch. I plan on upgrading soon only because when the shop was built (1954), the wiring was only rated at 50 amps and was directly buried in the ground, using the wrong type of cable. So.............I really need to re-do it to bring it up to snuff.

                Congratulations to Mr. "the sky is falling" Al Gore, nominated the new Village Idiot!


                • #9
                  thanks for all the suggestions, guys. i'll try the ts/shop vac combo without the auto start thing first and see if that makes a difference before i start fooling around with the wiring- after the blizzard clears up and the spring thaw hits later this week. i didn't think it got like this in texas...

                  thanks again,


                  • #10

                    I used to have the same power issues in our old house's garage, which only had 20 amp service total, for the whole garage)... which included overhead lights, a bench fluourescent light, all the outlets, and the garage door opener. I always had to start up my shop-vac first, let it to get to operational speed and then turn on the table saw or planer. Frankly, that little bench light sometimes was the straw on the circuit breaker's back. Forget about also running a heater or something else out there (get's cold up here in Wisconsin).

                    New house.. new basement workshop... I did all the electrical myself and made sure I had PLENTY of power capacity. 8 recessed lights - on their own 15A circuit, and front-of-shop / back-of-shop switches. I then installed two 20A circuits to power the outlets, using 12-3 wiring. I saw an interesting suggestion somewhere in some woodporn mag about using a 4" wide strip of plywood as a sort of divider midway up the wall to help hang drywall, but also to allow easy access to the wiring (if ever needed).

                    So I put outlets every 4 feet (I'll never need an extension cord again!) and alternated the active circuit per outlet. Gray outlets are on one circuit and the white ones are the other circuit (5 white, 4 gray), which makes it easy to visually make sure I'm not overloading anything. Since I use two shop-vacs for DC, I have one on each circuit, and they are strategically located / used to not correspond to the active machine. E.g. table saw goes on gray, so I use the white outlet shop-vac... Same with the router. For my planer, however, I use the other shop-vac and put the planer on the white circuit.

                    Long explanation to basically say my days of brown-outting the lights or tripping a breaker are long gone. I haven't given the shop a super-stress test by running every machine simultaneously... and don't plan to! TS, planer, router, bandsaw, drill press, mortiser, sander, jointer and two shop-vacs would probably cause my house to spontaneously combust!


                    • #11
                      Re: replace 15 amp with 20 amp?

                      well here are two links to the bt3central website (woodworking forums) that would give you some interesting information. i learned quite a bit from reading these post, hopefully they will help you aswell:



                      now, i dont know if you have to be a member to see the post. either way, if you are not already a member at that site, i would DEFINATELY suggest that you sign up, really nice website with lots of helpfull stuff and people.