Looks like, for now, the rule stating that a conductor must serve 100% of the dwelling unit's load to use Table 310.15(B)(6) is going away:
6-88 Log #3064 NEC-P06 Final Action: Accept in Principle
Submitter: Mike Holt, Leesburg, FL
Recommendation: Revise text as follows:
(6) 120/240-Volt, 3-Wire, Single-Phase Dwelling Services and Feeders. For individual dwelling units of one-family, two-family, and multifamily dwellings, conductors, as listed in Table 310.15(B)(6), shall be permitted as 120/240-volt, 3-wire, single-phase service-entrance conductors, service-lateral conductors, and feeder conductors that serve as the main power feeder(s) to each dwelling unit and are installed in raceway or cable with or without an equipment grounding conductor. For application of this section, the main power feeder shall be the feeder between the main disconnect and the panelboard(s) that supplies, either by branch circuits or by feeders, or both, all loads that are part or associated with the dwelling unit. The feeder conductors to a dwelling unit shall not be required to have an allowable ampacity rating greater than their service-entrance conductors. The grounded conductor shall be permitted to be smaller than the ungrounded conductors, provided the requirements of 215.2, 220.61, and 230.42 are met.
Substantiation: This proposal changes this section back to the 2005 code language. Requiring the feeder to serve the entire load in order to use this section simply does not make sense. For example, consider a 200A service for a dwelling. If the installation consists of a single 200A breaker, 200A feeder and 200A panel, the user can use this section. If the air conditioners for this house are removed from the 200A panel and put outside at the service equipment, there is now less load on the feeder conductors, yet the according to the 2008 revision to this rule, I must now make the conductors larger to serve a smaller load! Obviously this doesn’t make sense.
Panel Meeting Action: Accept in Principle
Panel Statement: See panel action on Proposal 6-83a.
Number Eligible to Vote: 11
Ballot Results: Affirmative: 11