Subpanel Breaker Box

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  #1  
Old 03-27-16, 11:32 AM
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Subpanel Breaker Box

I own an old church that has a large main shutoff for electric, a main panel with a 200 amp breaker, then 2 breaker boxes with no main breaker. I wanted to get rid of the old wiring that powers one of the sub boxes and update it since it is the only box with old wiring to it. Since there is no main breaker and trusting the old electricians did it right the total power of the breakers came out to 200 amps.
 

Last edited by TheManor; 03-27-16 at 12:36 PM.
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  #2  
Old 03-27-16, 11:38 AM
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It is wired to the main lugs but I don't see evidence of it coming off a breaker in the main box. I'm guessing I could use a 3-3-3-5 since the run is only about 15 feet?
 

Last edited by TheManor; 03-27-16 at 12:36 PM.
  #3  
Old 03-27-16, 05:27 PM
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Sum of all the breakers in the panel is meaningless. It can go over 200A main breaker without problem because you will not be putting full load on all the circuits. If that ever happens, main breaker will trip.

There is nothing wrong with using sub-panels without main breaker if it is within the same building. It is main lug connection. There will be a breaker in the main panel or another sub-panel that feeds this sub-panel. If not, it is done incorrectly and you have to find how it is connected and fix the problem.
 
  #4  
Old 03-27-16, 05:31 PM
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How did you come up with 200 amps for the box? You do not just add up values on the breaker handles. You need to find out what the box is rated for. Once you find out the box rating then you can either use the max for the box or do a load calculation of everything that is attached to the box. There are specific calculations

You do need to find out where this box is fed from. It may not even be from the main box.

3-3-3-5 copper is good for 100 amps.

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  #5  
Old 03-27-16, 08:01 PM
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3-3-3-5 copper is good for 100 amps.
I have never seen #5 wire.

You need 3 - #3 copper and 1 -#8 copper for the ground for 100 amps. The wire needs to be protected by a breaker or a fuse unless it feeds into a panel with a main breaker. (tap rule)
 
  #6  
Old 03-27-16, 09:45 PM
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I have never seen #5 wire.
I never have either but it sounded good!

I personally like thhn 3-3-4-8.
 
  #7  
Old 03-28-16, 08:04 AM
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Does the main box have feed-through lugs that are powering the sub boxes? These are hot lugs mounted directly on the bus bars of the main panel with no breaker? If so, this may need to change your plan a bit.
 
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