Re: Maximum Size Breaker for #12 Branch
Don,
I'm not sure but it seems that the commentary found in the 2005 NEC Handbook in the last sentence or so seems to suggest that supplementary OCP is limited in application....
(not arguing with you on this at all just trying to see it from all sides
)
Pete
Supplementary Overcurrent Protective Device. A device intended to provide limited overcurrent protection for
specific applications and utilization equipment such as luminaires (lighting fixtures) and appliances.
There are two levels of overcurrent protection within branch circuits: branch circuit overcurrent protection and supplementary overcurrent protection. The devices used to provide overcurrent protection are different, and the differences are found in the product standards UL 489, Molded-Case Circuit Breakers, Molded-Case Switches and Circuit-Breaker Enclosures, and UL 1077, Supplementary Protectors for Use in Electrical Equipment.
Provided as a generalization for understanding, the NEC requires that all branch circuits use only branch circuit ``rated'' overcurrent protective devices to protect branch circuits, but it permits supplementary overcurrent protection devices for limited use downstream of the branch circuit ``rated'' overcurrent protective device.
Added for the 2005 Code, the definition of supplementary overcurrent protection device contains two important distinctions between supplementary overcurrent protection devices and branch circuit overcurrent protective devices. First, the use of a supplementary device is specifically
limited to only a few applications. Second, where it is used, the supplementary device must be in addition to and be protected by the more robust branch circuit overcurrent protective device.