KLNR Series UL Class RK1 Fast-Acting Fuse. KLNR/KLSR series RK1 fuses were the earliest type of current-limiting fuse developed. Their single-element, silver link design enables them to provide fast-acting overload and short-circuit protection. When used to protect inductive loads such as motors, solenoids, and transformers, KLNR/KLSR series fuses must be greatly oversized to prevent opening the fuses on harmless inrush currents. In such applications, KLNR/KLSR series fuses may only provide short-circuit protection. We recommend using POWR-PRO LLNRK/LLSRK series RK1, dual-element, time-delay fuses in all new applications requiring the current-limiting ability of UL Class RK1 fuses, or in existing applications where fast-acting RK1 or RK5 fuses have been opening on harmless system surges such as motor starting currents. Applications: resistance heaters, lighting circuits, non-inductive loads, molded case circuit breaker load centers and panelboards have increased interrupting ratings when series rated with Littelfuse KLNR/KLSR Class RK1 fuses. Refer to panelboard manufacturer literature for UL Listed combination of fuses and panelboards. Series ratings up to 200,000 amperes are available.