Bussmann FRN-R 50A Fuse – Time-Delay Cartridge, 250V, IR 200kA/125Vdc and IR 20kA, 2-Pack

The Bussmann FRN-R 50A fuse is built for robust motor and main panel protection in industrial and commercial settings. This heavy-duty, time-delay cartridge fuse is designed to tolerate momentary startup surges while guarding circuits against longer overloads, helping you maintain smoother operation and reduce unscheduled downtime.

With a dual-element design, the FRN-R can open quickly under short-circuit conditions—as fast as 0.004 seconds—while still permitting brief overloads to pass during startup. The device carries UL Listing as Class R with an impressive short-circuit current rating (IR 200 kA). The end cap groove or knife blade notch makes it compatible with Class H, Class K, and Class R fuse blocks, enabling flexible integration into existing panels. These features pair with ratings suited for a wide range of applications where higher amp or volt ratings are required.

Key advantages

• Heavy-duty time-delay protection for motors and main panels
• Helps prevent motor burnout from overloads and single-phasing on three-phase systems
• Dual-element design provides strong short-circuit protection alongside overload tolerance
• General purpose vs heavy-duty variants allow use in lighting, heating, and motor circuits
• Motor overload and short-circuit protection in a compact cartridge fuse

Ideal uses and installation notes

• Industrial equipment, conveyors, pumps, and HVAC systems where motors require surge tolerance
• Control panels and branch circuits in commercial facilities needing reliable protection and selective coordination
• Residential and light-commercial settings that involve motors and higher amp circuits

What’s in the retail pack? A two-piece package that provides ready-to-use protection for replacements or stocking up for maintenance. The FRN-R series supports voltages up to 600Vac and can be found in a range of sizes and amp ratings to fit diverse equipment needs. When sizing, consider the motor or circuit load and the intended startup behavior to balance protection with uninterrupted operation.

Usage considerations

• Choose the heavy-duty time-delay variant to accommodate brief motor overloads and startup surges
• Confirm compatibility with Class R fuse blocks, and ensure proper mounting for reliable coordination
• Verify amp rating aligns with the specific motor or circuit load to balance protection and performance