230.4 exception #2

[ducks1333]

I've done a forum search and of course the issue of 230.4 ex. 2 being unclear was discussed. Your opinion please on this installation where the building has a single tenant. Please see the attached riser diagram. Panel MDP is an existing panel in a part of the building that was not demolished for the new addition. Can it be served from a separate disconnect switch located adjacent to my new main panel CMDP with the feeders from the transformer to the MDP disco and CMDP as shown? The more basic question is would this installation have two "sets" of service conductors or only one "set" per 230.4? The service point is the lugs of the transformer. CMDP has a main breaker. Thanks for you thoughts.

John Chapman

 

[ducks1333]

I should probably say never mind, I just found where is 230.2 it says that for the purpose of 230.4 ex. #2 that says if the conductor are 1/0 or larger and if they are connected together at the supply end then they shall be considered as one set for the purpose of 230.4 ex.2. Let me know if anyone disagrees or has anything to add.

Thanks,
John

 

[electrofelon]

I've done a forum search and of course the issue of 230.4 ex. 2 being unclear was discussed. Your opinion please on this installation where the building has a single tenant. Please see the attached riser diagram. Panel MDP is an existing panel in a part of the building that was not demolished for the new addition. Can it be served from a separate disconnect switch located adjacent to my new main panel CMDP with the feeders from the transformer to the MDP disco and CMDP as shown? The more basic question is would this installation have two "sets" of service conductors or only one "set" per 230.4? The service point is the lugs of the transformer. CMDP has a main breaker. Thanks for you thoughts.

John Chapman

You must be referring to 230.40. I see no problem with the design. Yes you would have two setsof service entrance conductors, each of which may be run in parallel. Your GEC tap to the smaller enclosure is unnecessarily large.

 

[ducks1333]

Thanks, yes I meant 230.40.