July 20, 2010 – Underwriters Laboratories (UL) officially established a new fuse and fuse holder class for the next generation of circuit protection. The new Class CF, UL File numbers E4273, Vols. 6 & 7, and standard 248-17 for the fuse and 4248-17 for the holder, provides the same electrical protection of a Class J, along with finger-safe construction and smaller dimensions than the Class J fuse standard. Currently only the Cooper Bussmann Low-Peak CUBEFuse overcurrent protective system – both the fuse and fuse holder – meets the new Class CF standard.The CUBEFuse system had been previously designated as “Special Purpose” Listed Class J.
The new Class CF listing removes the "Special Purpose" category and its unique marking as well as removes confusion in the industry over whether the CUBEFuse can be used where a “Listed” fuse is required. The new Class CF is the first class with Peak Current Let-Through Curves in the standard. These curves cover the range of currents from 25kA to 300kA, and allow users to pick any available current they want. This same concept is working its way through the standards process for Class J, L and RK1.