Sub Panel -- When is a main required???

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  #1  
Old 07-24-04, 06:12 AM
rikamy
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Sub Panel -- When is a main required???

Just a quick question, I got into a debate with the general on my job on a room addition.. I'm converting the existing panel into a 100 amp sub, and pulling new wire to a new panel... I've been told that in a sub panel, anything over 6 spaces (12 circuits) has to have a main disconnect means and cannot just be lugs only..... Still looking in the code book... The general seems to think you never need a main breaker for a sub,, lugs only o.k... anybody know the specifics on this one???? I've looked it up in NEC 2002 and think I have found it in 230.71
 

Last edited by rikamy; 07-24-04 at 07:30 AM.
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  #2  
Old 07-24-04, 08:02 AM
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"Service Conductors" ( definition)---- "The conductors from the Service-point to the Service Dis-connecting Means"

You have mentioned two panels/enclosures. In which one of these two do the Service Conductors terminate on the Service Dis-connecting Means?

Good Luck & Enjoy the Experience!!!!!!!!!!
 
  #3  
Old 07-24-04, 09:33 AM
rikamy
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Thanks for the reply....... Service conductors are going into the new service panel that I've mounted outside of the garage.. The existing panel (200 amp service) will be converted to a 100 amp sub-panel.. All of my heavy loads will be spliced and ran to the new panel with the addition of any new circuits pulled for the room addition. The existing panel to be converted to a sub panel will have about 14 circuits on the general lighting rececptacles load.. My interpretation of the code is that this sub panel will have over six circuits, therefore needing its own disconnect.. The new service panel will not be in plain view from the sub panel, it will be located inside the house.. My interpretation is that a 100 amp breaker located at the new service panel will not be sufficient means of disconnect and that the sub panel will also need a 100 amp breaker for disconnect?? is my interpretation of the code correct??
 
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Old 07-24-04, 10:03 AM
CSelectric
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code specifically requires a main disconnecting means (either a main breaker at the main panel, or a disconnecting means prior to the main panel. There is no code requirement for a main breaker on a sub panel, as long as it is fed via a breaker in the main panel. The only time a main breaker would be required is if the subpanel is fed from a point in the service before the main disconnect of the other panel (ie: secondary lugs on the meter base), in which case the second panel is not a subpanel at all, but a second main panel. Of course, if this is the case, the two panels in question would need to be located adjacent to one another to meet the "closely grouped" requirements of the six disconnect rule (230.72 (2002)).

Your reference to 230.71 (2002) is incorrect. that article pertains to service entrances (ie: the main panel) and has no bearing on subpanels. Incidentally, the six disconnect rule is just that, a limit of six. A six space panel that is rated for tandem breakers would not meet this code requirement. six tandem breaker = 12 disconnecting means = a violation of 230.71 (2002).
 
  #5  
Old 07-24-04, 10:40 AM
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In general, Neither "Feeders"--- the conductors extended from the Service-panel,or panelboards are required to have a "Dis-connecting Means".

A C-B panel connected to "tap" conductors would be required to have a C-B that would limit the currrent to the panel to an current-value equal to the ampacity of the tap-conductors.

A panel located in a stucture seperate from the structure where the Service is located would be required to be connected to the "Load" side of a Dis-connecting Means for the seperate structure. The relevant Article is 250.32 (D) , the Code-section on Grounding.
 
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