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Old 03-24-2008, 06:40 PM   #16
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Just look over books that cover subpanels for attached and detached structures. This should help you out a lot. Some books (Black & Decker for instance) call it advanced wiring.

Having the subpanel wired using the 3conductor + ground (as mentioned) allows you to seperate the 120v and 240v at the subpanel. No other wiring would be necessary from the main to the subpanel.


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Old 03-24-2008, 07:30 PM   #17
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Hello Rob

Whew.... I was hoping some of the other guys would show up to help you out.
When you get your book I want you to pay particular attention to how you get 240 volt branch circuits and 120 volt branch circuits. This is done with double pole breakers for 240 volts and single pole breakers for 120 volts. They look like this......

Double Pole 240 volts

Single pole 120 volts

All the guys here will explain all this as we go right now we need to get you through the sub-panel installation.

Your going to need 100 amps so your going to need a 100 amp double pole breaker for protection of the 4 wire feeder to the shop sub-panel.

Also I see the shop is attached so we can eliminate having to have ground rods. You will need a 4 wire cable unless you want to run conduit. I would run a cable since the shop is attached. You can use aluminum or copper your choice aluminum will be bigger and a little harder to handle than copper. this is a copper 4 wire cable if you choose copper it will need to be #3 awg and will have 2 hots, one neutral and a ground the bare or green is your ground. The neutral will have a white stripe on it or some other identification, the other two will be your hots. If you use aluminum you will need a #1 awg cable. You are going to want SER cable that will allow 100 amps using #3 copper or #1 aluminum. Other cables like NM_B will not allow 100 amps on #3.... these cables will need to be #1 copper.
See the image below it is a typical SER cable.... Also I'm going to post a diagram of the wiring... main panel to sub-panel.... in a hour or so so check back.
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220V 100A Circuit-4-wire-cable.jpg  

Last edited by Stubbie; 03-24-2008 at 07:44 PM.
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Old 03-24-2008, 09:10 PM   #18
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This diagram below shows how things will look. Pay particular attention to how the shop sub-panel has two bars that are not electrically connected. In a sub-panel the neutral bar is isolated from the ground bar as shown. The ground bar will be in direct contact with the metal of the cabinet and may require you to purchase a ground bar kit as the panel may not come with it. When you buy your 100 amp sub-panel you can get one called main lug that does not have a main breaker in it. Get one that has enough spaces and circuits for your needs. Remember your 240 branch circuits going to your equipment require 2 full spaces in the sub-panel. Might go look at them and copy down the models #'s for us and we can tell you what is what about them. In the event you would like to have a main breaker in your sub then look at those too. Give us the model#'s and we can explain them. the big box stores usually have square d, seimens, General electric and cutler hammer plus others depending on the part of the country you are in. Click on image to enlarge.
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220V 100A Circuit-4-wire-feeder-same-building.jpg  

Last edited by Stubbie; 03-24-2008 at 09:17 PM.
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Old 03-24-2008, 09:21 PM   #19
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You can buy a panel at lowes that is for a "workshop". It comes WITH the grounding bars all setup and ready to go!!


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