Cooper Bussmann FRS-R-50 50A RK5 Time Delay Fuse

Product Description

The COOPER BUSSMANN FRS-R-50 is a cartridge-style, time-delay fuse rated at 50 amps and classified as RK5. It is designed for general-purpose overcurrent protection in industrial and commercial electrical systems. The dual-element construction allows the fuse to carry temporary inrush current surges without nuisance opening, while still providing fast, reliable response to sustained overloads and short-circuit faults. At 27 millimeters in diameter and 5.5 inches in overall length, the FRS-R-50 installs into a standard fuse holder and is sized for use in motor branch circuits, HVAC equipment, and general distribution panels. Licensed electricians and qualified electrical technicians are the primary installers.

The FRS-R-50 is suited for residential, commercial, and light industrial applications where RK5-class protection is specified. Common use cases include motor branch-circuit protection for HVAC compressors, condensing units, air handlers, and pump motors where inrush current during startup would trip a standard fast-acting fuse. The time-delay characteristic makes it particularly appropriate for equipment with high locked-rotor amperage relative to running amperage. Non-indicating design means no visual blown indicator is present; a fuse tester or continuity check is required to confirm fuse condition during service.

Key Features

• 50-amp rating with time-delay (dual-element) construction for motor-load applications
• RK5 fuse class — dimensionally interchangeable with RK1 fuse holders
• 20 kA interrupting capacity at DC 200 V RMS for short-circuit protection
• Non-indicating design — no blown indicator window
• Cartridge body, 27 millimeters in diameter and 5.5 inches in length, mounts in standard fuse holder
• CE Certified, CSA C22.2 No. 248.12 Certified, and UL Listed 248-12 Class RK5

Compatibility

Designed for use in RK5-class fuse holders accepting a cartridge fuse body of 27 millimeters in diameter and 5.5 inches in overall length. Dimensionally compatible with RK1 fuse holders of the same size class per applicable UL and CSA standards.

Installation Notes

Installation and replacement of branch-circuit fuses must be performed by a licensed electrician in accordance with the National Electrical Code (NEC) and all applicable local codes. Always de-energize and lock out the circuit at the panel before removing or inserting a fuse. Use an insulated fuse puller rated for the voltage of the circuit — never pull a cartridge fuse by hand or with uninsulated tools. Verify the replacement fuse ampere rating and class match the circuit protection requirements before restoring power.