Running subpanel

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  #1  
Old 04-28-12, 10:37 PM
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Running subpanel

Hello!

I am doing some work in a new room and need to run some new outlets and a few lights. I went to my breaker box and as I feared am out of room. (currently using a 200amp box) I wanted to put in another 100amp or 60 amp box, but would prefer 100 so I do not need to go through this mess ever again.

Here is my current plan,
  1. Buy a 100amp box as well as a 100amp breaker and required cables.
  2. Cut off the house power (entire house)
  3. Wire up the 2 hots to their respective lugs, and neutral to its bus, ground to its
  4. Remove the service ground from this box to meet code and run any ground to the actual main service ground..
  5. relocated displaced breakers from 200amp to the new box
  6. Run required cables for outlets into breakers & let there be power!


Now I could most likely put these onto one breaker in a room that doesn't get used at all (storage) but would rather run this box, mostly for the future generator I want attached to this box't, but also to ensure I don't over load anything. before I go ahead and tackle this project I am held up by one question, how can I tell if there is enough amps to add the box?


Thank you in advance!!!
 
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  #2  
Old 04-29-12, 06:00 AM
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Two things. To determine if the service is large enough or to properly size a subpanel you perform a demand load calculation. The other issue is you will not be able to bring a generator feed into the subpanel. It needs to be interlocked at the service panel.
 

Last edited by pcboss; 04-29-12 at 06:53 AM.
  #3  
Old 04-29-12, 06:40 AM
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Remove the service ground from this box to meet code and run any ground to the actual main service ground..
I think you understand by this but to be clear, you do not bond the neutral buss bar to the steel can of the 100 amp panel. You will install a ground bar (or 2) and all your grounds will go to that bar(s). I think what is throwing me off is "actual main service ground".
 
  #4  
Old 04-29-12, 07:24 AM
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Yes, when I read this in one of the guides I was looking at I was researching why, it was explained to me that if this is NOT done then sometimes the ground can carry a current given from the neutral. So when you remove the service ground the ground bar will end up going to the main breaker's service ground correct?
 

Last edited by stickshift; 04-30-12 at 07:54 AM. Reason: removed quoting of entire post
  #5  
Old 04-29-12, 08:20 AM
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In your main service panel (200amp) the grounds and neutrals terminate in the same location. The neutrals and grounds will remain at the same place.

In the subpanel (100amp), the grounds and neutrals will be separated and the neutral bar will "float" (not attached to the metal can).

The circuits that you relocate to make room for the new breaker to feed the subpanel, should also have the neutrals relocated with the hot wires, and terminated in their proper place.
 
  #6  
Old 04-29-12, 06:19 PM
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You may want to stick with a 60A feed to a 100A panel. The [#6] is much easier to work with than the larger wire needed for the 100A. As long as you just run your smaller loads and your 15/20A circuits off your subpanel, I can't imagine you needing more than a 60A feeder.

Just something to consider...
 

Last edited by ray2047; 04-30-12 at 11:00 AM. Reason: Correct typo.
  #7  
Old 04-30-12, 07:27 AM
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A 60 amp feed will require #6 copper.
 
  #8  
Old 04-30-12, 09:20 AM
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Oops - thanks for the correction Tolyn. (I tried to edit my post to eliminate confusion, but it seems I can't. Oh well)

Still, #6 is easier to work with!
 
  #9  
Old 04-30-12, 02:48 PM
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I like the idea of a demand load calculation being done for the additional loads (Hint: loads on a Branch circuit) being added!!
 
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