Garage Shop Wiring Questions

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  #1  
Old 01-12-12, 11:11 AM
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Garage Shop Wiring Questions

I have a 3 car garage and am in the process of converting 1 bay into a workshop.

There is a 30 amp 240V breaker at the main panel that serves a 4 space sub panel in the shop space. All of the walls and ceiling in the garage are finished drywall and there is a 120V outlet in the ceiling for the Garage Door Opener (15 amp circuit on the house sub-panel) as well as a few other 120V 20 amp outlets in the garage walls.

I have installed a 240V 20 amp breaker in the sub panel to provide power to my table saw and the cable is protected in metal conduit to the 240V outlet. I've also added another 120V 20 amp circuit in the wall adjacent to the shop space for miscellaneous small tools.

I need to add some ceiling fluorescent lights as well and was wondering if I couldn't simply tap off of the existing ceiling outlet with switch wiring run in NM conduit to a surface mounted switch box. I have access to the space below the shop (wood floor construction) so if I need to run any additional circuits to be surface mounted (maybe for a dust collector or other special equipment) I can do that the same way as I did for the table saw.

Is there anything wrong with the above?
 

Last edited by Joe.Carrick; 01-12-12 at 12:59 PM.
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  #2  
Old 01-12-12, 11:47 AM
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Is this a commercial or residential garage? Commercial work would likely require a licensed contractor to perform the work.
 
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Old 01-12-12, 12:20 PM
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It's residential - my own home and the Garage is attached. The main service panel is on the outside of one wall (exterior of course) and the shop area has it's own roll-up door. But the shop area is only partially separated from the rest of the garage.
 
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Old 01-12-12, 12:23 PM
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ps: I am very competent with doing electrical wiring in general - mostly I'm just checking to make sure there's no code problems that I haven't covered.
 
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Old 01-12-12, 12:44 PM
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ps: I am very competent with doing electrical wiring in general - mostly I'm just checking to make sure there's no code problems that I haven't covered.
I question your "competency". Being competent is a whole lot more than just being able to staple type NM cable without damage or having your completed project work.

Knowing basic codes IS part of competency and so is knowing that in single-phase residential work the lower voltage is almost always 1/2 of the higher voltage and that nominal voltages in single-phase residential work have been 120 and 240 for about the last half-century unless you live 100 miles into the sticks.
 
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Old 01-12-12, 12:55 PM
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OK, so I said 110V instead of 120V and 230V instead of 240V. That doesn't change the fact that I know how to do a quality job with proper grounds, connections, etc. I have done all of the electrical wiring on many new homes (except for the main-service) with inspections. I am not a licensed electrical contractor but I do have many years of experience.

ps: If it makes you any happier, I have changed those errors in my original post.
 
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Old 01-12-12, 12:58 PM
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Actually probably closer to 70 years behind the times.

I need to add some ceiling fluorescent lights as well and was wondering if I couldn't simply tap off of the existing ceiling outlet with switch wiring run in NM conduit to a surface mounted switch box.
I'd suggest a larger breaker box and a separate circuit for the lights. If the breaker box is fed by conduit you might even consider upping it to #8 on a 40a breaker. Once you get a craving for power tools you never know what's next. Dust collector to keep the sawdust out of the rest of the garage maybe?

Assumes a detached garage.
 
  #8  
Old 01-12-12, 01:23 PM
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Thanks Ray,

The breaker box is not fed by conduit. The feed to the box is only about 30 feet total with #8 wires (3+g). I only need a couple of 2-tube fluorescent fixtures for lighting and I can't run more than the table saw and my 120V dust collector at the same time. It's a one man shop and I have no tools that draw more than 8 amps. Currently I'm only using 3 of the 4 spaces in the box. One for the 120V (dbl 20 amp breaker) and two for the 240V system. Since I'm using all thin breakers I have (1) 240V and (3) 120V breakers as spares. As I said previously, there are also existing garage circuits for outlets and lighting from the house sub-panel.

IAE, I've decided to connect the new light fixtures to the existing garage lighting circuit and just provide a separate switch leg for the shop area lights. If I need additional circuits in the future (extremely unlikely) it will be easy to use the spare breakers. I have an access panel to the stud space where the shop panel is located so running the wiring will never be a problem.
 
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Old 01-12-12, 03:03 PM
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BTW, my cyclone dust collector is only a 1.5 hp motor. I non-insulated ground wire in all the ABS dust pipes to prevent a dust explosion and blast gates at each tool connection point. I used to have a 240V air compressor but that was total overkill. I only use a small pancake type compressor now so a 15 amp 120V circuit is quite adequate for that. Maybe I'll need the 240V for a Welder but I could just unplug the Table Saw and plug in the Welder.
 
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Old 01-12-12, 03:16 PM
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As I said previously, there are also existing garage circuits for outlets and lighting from the house sub-panel.
If you mean other then the subpanel in a garage this is a major code violation if it is not an attached garage. Is it attached?
 
  #11  
Old 01-12-12, 03:22 PM
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Yes, it's attached as I said in a previously in post #3. The house sub-panel is in the garage next to the door going into the house. The shop sub-panel is located on the wall that's partially separates the shop and the rest of the garage space.
 
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