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Thread: Small Shop Wiring

  1. #1
    DIY Junior Member Mike Turner's Avatar
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    Default Small Shop Wiring

    "I have a 200 amp service in my house. I have a small shop. I ran 10-2 with grd off of a 20 amp breaker from the 200 amp service to a 30 amp fused service disconnect. The distance from the 200 amp service to the 30 amp disconnect is about 75 ft.. In my shop the only thing that stays on is a small freezer...I have the service disconnect in the shop fused with 15 amp fuses. I have 2 circuits coming from it.. Most of the time only a fluorescent light, a box fan , the freezer and a drill press or other tool might be going but not a bunch of tools at the same time...I have a 1 hp motor on a lathe that is used in it...I have used it this way for 15 yrs for the most part..The lathe is a recent addition ...When I do need to use something else I usually run a drop cord from an outlet on the outside of my house...not a long run at all.. 12-2 is run to everything in the shop..Nothing smaller was used at all. I have rarely tripped the breaker or blown any fuses at all.. Should I change any of this?? If I change the 20 amp breaker to a 30 amp one I assume that would allow me to not use any more than 30 amps before it tripped???? Thanks, Mike Turner

    Thanks, Mike Turner"

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    Jack of all trades DonL's Avatar
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    Welcome to Terry's forums Mike,

    Normally you would have a larger breaker in the main box, then limit the smaller current needed for the garage in it own box.

    I would feed a 30 to the 20, not a 20 to a 30, as it would never trip if really needed.

    I am not sure if I understood your question, forgive me if I HMHUMA.

    That is just my thought, but the pros will show up shortly, To help you.


    Have a Great Day. Good luck on your project.


    DonL
    Last edited by DonL; 06-29-2011 at 11:39 AM.
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    General Engineering Contractor ballvalve's Avatar
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    Should I change any of this?? If I change the 20 amp breaker to a 30 amp one I assume that would allow me to not use any more than 30 amps before it tripped???? Thanks, Mike Turner
    Yes, that would make some sense.....

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    DIY Junior Member Mike Turner's Avatar
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    Thanks for the welcome. Right now there is a 20 amp breaker in my main service feeding to a 30 amp square D fused disconnect....the kind with 2 screw in fuses..I have two 15 amp fuses in there and it feeds 2 circuits in the shop. I am not an electrician by any means but I did take some classes yrs ago so any advice is appreciated..... I did this 15 yrs ago and havent had any problems ....very rarely tripping a breaker...blown fuse rarely....But Ive started using a little more stuff lately...a wood lathe with a 1HP motor and sometime I have to use my small air compressor when lathe is running BUT I run it off an outside outlet on the house ....Soooooo I want to definitely be safe. My question is would it be best to change the 20 amp breaker in my main disconnect to a 30 amp one ???

    Question 2.....In the 30 amp disconnect I have 10-2 with ground going into it .It feeds to one of the 15 amp fuses / circuits/ line and then I have a jumper going to the other side/line or fuse to send it power. Is this correct? Again guys thanks for all your help !!!

  5. #5
    Test, Don't Guess! cacher_chick's Avatar
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    If you are planning on expansion you will want 240V. If this is a seperate building and you want more than one circuit, it will require a subpanel and grounding rods at the outbuilding.

  6. #6
    In the Trades SacCity's Avatar
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    Quote Originally Posted by Mike Turner View Post
    20 amp breaker in my main service feeding to a 30 amp square D fused disconnect....the kind with 2 screw in fuses..I have two 15 amp fuses in there and it feeds 2 circuits in the shop.
    My question is would it be best to change the 20 amp breaker in my main disconnect to a 30 amp one ???

    Question 2.....In the 30 amp disconnect I have 10-2 with ground going into it .It feeds to one of the 15 amp fuses / circuits/ line and then I have a jumper going to the other side/line or fuse to send it power. Is this correct? Again guys thanks for all your help !!!
    10/2 is good for a 30 amp service so no problem there, the intention is to have the breaker protect the wire so increasing the breaker in the main panel to 30 amps is fine.
    In the sub-panel you can run to 20 amp circuits off the 30 amp service. The jumper between the two is a good way to go. Better would have been to run a 10/3 to the garage but that was 15 yars ago and its worked fine so don't muck with it if you don't need to.
    12/2 is good for 20 amps, and 14/2 for 15 amps so with the 12/2 wire you are fine.
    Michael
    Sac City Plumbing
    http://SacCityPlumbing.com

  7. #7
    DIY Junior Member Mike Turner's Avatar
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    Last ? on this ...I am using 2 15 amps fuses right now. I can change those to 20 amps one right? Or would you stay with 15 and 15 for 30 amp service ? Is my thinking of the 2 15 amps ones as adding up to 30 amps. Maybe someone can clear my mind on these. I know these are elementary ? for you guys but thanks !

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    Electrical Contractor jbfan74's Avatar
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    What size is the wire leaving the disconnect box?

    If it is 14, then you cannot change the fuses.
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  9. #9
    DIY Junior Member Mike Turner's Avatar
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    It is 12-2 . Actually it is 12-2 to everything..... No 14 used at all. Thanks !
    Last edited by Mike Turner; 07-01-2011 at 12:40 AM.

  10. #10
    Moderator & Master Plumber hj's Avatar
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    If the wires are #12, then you can use 20 amp circuit breakers, (I hope you do not still use fuses). Any overload in the sub panel, regardless of the breaker sizes in the sub panel, will trip the 30 amp main breaker. Whoever installed 10/2, instead of a 10/3, originally did NOT do you any favors. (I might also have used at least some 12/3 INSIDE the garage.) And you might need a ground rod at the garage to be completely legal.

  11. #11
    DIY Junior Member Mike Turner's Avatar
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    The wires are 12-2. There is a good ground rod outside of shop. I'm the guilty one installing the 10-2 instead of 10-3 15 yrs. ago before I knew what the 10-3 was even for like in this situation....Everything has been working fine for all these yrs. Does anyone see any need to change the wiring ? What I have in the shop is a sq D 30 amp disconnect with 2 of the round fuses..not the long type.....I just changed the breaker in main service from a 20 amp to a 30amp yesterday....Over these 15 yrs it has only tripped the 20 amp breaker in main panel maybe 3 or 4 times.. Is there any reason to change out the sq d disconnect? Thanks

  12. #12
    Jack of all trades DonL's Avatar
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    Mike,

    I would leave it as is.

    But make sure all your tools are grounded properly, for your own safety.

    There is no reason to spend a bunch of money, to gain nothing.


    Enjoy your Holiday.


    DonL
    Theory only works perfect in a vacuum.

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  13. #13
    Test, Don't Guess! cacher_chick's Avatar
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    There is no requirement to change an installation that met code when it was installed.

  14. #14
    DIY Junior Member Mike Turner's Avatar
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    I was really just wanting to make sure everything was very safe. I sometimes lean to the extreme side. but everything has worked fine all these yrs but I do use the shop a little more now but I am cautious about using too much at one time! Thanks everybody for all the answered ? and input !!!!

  15. #15
    Test, Don't Guess! cacher_chick's Avatar
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    Probably the biggest single improvement you could make would be to install GFCI receptacles. I believe they are now required in all garages.

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