Shop subpanel feeder for rgray422

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Old 03-21-09, 10:57 PM
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Shop subpanel feeder for rgray422

hey guy...im new to this site and found your response to a similar predicament and thought you may be able to help me. ive been a professional cabinetmaker for almost 30 yrs and just now building my own small shop at home, approx. 500 sq ft. i plan on wiring a sub panel to my shop from my main panel which has plenty of room for it. im not an electrician but during my years of construction i have picked up some knowledge. an electrical contractor on a previous job gave me this advice when i told him what i was planning. he suggested a 6/3 and #10 ground to the shop....im planning on a 220 line for a table saw in the future.....a 100 amp breaker at the incoming panel and a 30 amp for the 220 and two 20 amps for lighting and outlets at the subpanel. what do you think?
 
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Old 03-21-09, 11:05 PM
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rgray--

If you want to use 6/3 cable for the shop subpanel, you'll need to use type UF-B waterproof "underground feeder" cable instead of the usual NM-B "non-metallic romex" which is not waterproof. This type of cable can power a 60A subpanel at a distance of up to about 150'. If the distance from the house to the shop is longer than that, you'll need to select a larger cable.

A 60A panel should be sufficient for shop lighting and wood working tools. If you plan to use metal working tools like a welder or plasma cutter, then a 100A subpanel with appropriate sized cable may be required.

You will need to install a ground rod at the shop, bonded to the subpanel ground bar using #6 copper wire and an acorn clamp. The subpanel needs to have isolated ground and neutral bars; this usually requires you to purchase an add-on ground bar kit for the panel and to remove the factory-installed bonding screw or strap.

Instead of installing any cable or breakers for your future table saw, I recommend that you install a 1/2 or 3/4 conduit from the shop subpanel to the expected table saw location. You can then install the correct size wire and breaker when you select the table saw.

A 500 sq. ft. shop will likely require more than two 20A circuits. I would start with one 20A for lighting and then run a dedicated 20A circuit to each tool location, and a general-purpose 20A circuit to each "workbench" location. You also may want to consider a 20A circuit on a cord-reel hung from the ceiling. All 120V receptacles must have GFCI protection. Don't forget the exterior lighting which is required at all grade-level entrances.
 
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