Cooper Bussmann FRN-R-40ID RK5 Time Delay Fuse 40A

Product Description

The COOPER BUSSMANN FRN-R-40ID is a Class RK5 cartridge-style time delay fuse rated at 40 amps for use in general-purpose AC and DC electrical circuits. The dual-element design provides time delay characteristics that allow temporary inrush currents to pass without nuisance opens, while still providing fast response to sustained overloads and short-circuit faults. The fuse measures 3 inches in overall length and 0.81 inches in diameter, fitting standard RK5-class fuse holders. It carries CE, CSA, and UL listings, making it suitable for installations requiring certified overcurrent protection. Electricians and industrial maintenance technicians are the primary installers of this component.

This fuse is applied in motor branch circuits, HVAC equipment, industrial control panels, and similar loads where temporary inrush current is expected at startup. The time delay characteristic prevents nuisance opening during motor starting while still protecting wiring and equipment from sustained overcurrent conditions. The indicating feature allows visual confirmation of a blown fuse without the need for a meter, speeding up troubleshooting in panel and disconnect applications. It mounts in any compatible RK5 or RK1 fuse holder configured for the cartridge form factor.

Key Features

• Dual-element time delay design handles motor inrush without nuisance opens
• 40-amp rating with 20 kA interrupting rating at DC 200 V RMS
• Indicating fuse — visual blown indicator for faster fault diagnosis
• Class RK5 cartridge form factor: 3 inches OAL, 0.81 inches diameter
• UL Listed 248-12 Class RK5 (Guide JDDZ, File E4273), CSA C22.2 No. 248.12 Certified, CE Certified
• Fits standard RK5 fuse holders — no adapter required

Compatibility

Designed as an OEM-style replacement or service fuse for any RK5-class cartridge fuse holder rated for 40 amps, 3 inches OAL, and 0.81 inches diameter in general-purpose branch circuit and motor circuit applications.

Installation Notes

Installation must be performed by a qualified electrician in accordance with the National Electrical Code (NEC) and applicable local codes. De-energize and lock out the circuit at the disconnect or panel before removing or installing any fuse. Verify that the fuse holder is rated for Class RK5 cartridges and that the circuit voltage and amperage do not exceed the fuse ratings. Do not substitute a higher-amp fuse to resolve nuisance opens — diagnose the underlying load or inrush condition instead.