The Capacity Requirements circumstance [230.2(C)] and the Different Characteristics circumstance [230.2(D)] differ from their counterparts in Art. 225 of the NEC. How so, and why?
The first thing you might notice is where these are located in Art. 230. Typically, the XXX.2 subsection provides definitions of terminology for that Article or, if there aren't Article-specific definitions, then there is no XXX.2 subsection. While not a technical error, it is an inconsistency that can be confusing.
Subsection 225.30(C) exactly matches 230.2(C)(1). The difference in the two subsections is that, for services, you have two additional situations that may qualify for a capacity requirements exception:
- The load requirements of a single-phase installation exceed the size of what the serving agency (e.g., electric utility) normally supplies through a single service [225.30(C)(2)]. Rather than go through custom engineering and installation, you can just add another service.
- By special permission [225.30(C)(3)]. Here, the NEC allows some leeway rather than try to create a laundry list to cover all possible reasons. What stops this from being a free for all is you have to make your case to the Authority Having Jurisdiction (AHJ) to get that special permission.
Subsection 225.30(D) exactly matches 230.2(D), except:
- 225.30(D) allows for additional feeders, 230.2(D) for different services.
- For additional uses, 225.30(D) uses multi-location lighting control as an example while uses rate schedules.
