View Full Version : Power to outbuilding
jhill1961
Apr 28, 2011, 03:03 PM
What size wire is needed to supply a 60 amp subpanel that is 35 feet away to an outbuilding? The outbuilding will be a workshop and is 308 sq.ft. All the wiring in the building will be 12awg and plan on using 20 amp breakers. There will be 2 light, 1 dedicated, 3 receptical and 2 additional circuits. Thanks
ma0641
Apr 28, 2011, 03:26 PM
Are you planning to run Copper or Aluminum wire? Buried or overhead?
jhill1961
Apr 28, 2011, 04:11 PM
Am planning to run copper buried. Also will be using woodworking tools, compressor, tablesaw, router, chop saw etc.
donf
Apr 28, 2011, 05:10 PM
There are some very basic things you need to know.
First, you will need a four wire feeder from the main service panel to your panelboard in the shop.
If you bring electrical power into a remote building, you must install an exterior light at the entrance to the building.
The panelboard in the shop can be a MLO (Main Lug Only)panelboard or a MCB (Main Circuit Breaker).
If you choose a MLO panelboard, then you must have either a Main Disconnect switch or no more than six breakers in the panelboard. Personal, I strongly suggest the main disconnect switch. It is the most quick and safest way to cut power in the event of an emergency.
The panelboard in the shop must have "Neutral" and "Ground" isolated from each other. The only place where you can have ground and neutral meet is in the in service panelboard.
You must also install either a ground rod or if you have a metal cold water pipe that is buried and extends at least 10' from the building then you can bond the shop panelboard ground to that.
Now as to your load. You really have to do a load calculation to make sure that you are supplying the correct levels of voltage and amperage.
Any 120 volt receptacle in the garage should be GFCI protected, with the exception of receptacles that supply power to motor driven equipment.
You also must make sure that the motor, amperage, cables, cords and circuit breakers are properly sized for each motor to be used.
Not knowing the level of wood dust and/or fibers you might kick up, you must be able to protect the receptacles from contamination.
If too much wood dust or fibers collect inside of receptacles you could end up with an explosion or fire.
In most cases, I would suggest using a dust-proof receptacle box. A waterproof box would work fine.
There is a lot of work to planning a wood shop out for electrical service. Also, not knowing what your LAHJ requires, permits and inspections may be required.
ma0641
Apr 28, 2011, 07:34 PM
#6 THWN will get you 65 Amps and a little voltage drop in 35 ft. To be safe and allow power for saws, a compressor etc. #4 THWN goes 85 Amps. Might cost another $50 but well worth it. Are you familiar with the wiring of a sub-panel? Donf covered the details. It's not quite like running a big extension cord!
jhill1961
Apr 29, 2011, 07:29 AM
I am a carpenter by trade and have over 20 years in the building industry. I will be running all the wiring myself with the exception of the final hookups at the panels. That I will leave to an electrican. I do have all permits needed and have very detailed plans for my workshop as to where all tools, lights etc. will be placed. Thanks for the info.