Overview
The Bussmann FRS-R-4 is an industrial-grade dual-element, current-limiting cartridge fuse designed for motor and transformer overload protection. This Class RK5 fuse features a 4A rating with interrupting capacities of 200 kA at 600 Vac and 20 kA at 300 Vdc. Engineered for energy efficiency and superior protection, the FRS-R-4 reduces nuisance trips while delivering reliable short-circuit and overload protection in industrial control circuits.
Key Features
- Dual-element, current-limiting time-delay fuse design for energy efficiency
- 10-second time delay at 500% rated current, allowing motors to safely start without false trips
- Optional open fuse indication on select ratings (non-indicating version supplied)
- Class RK5 cartridge fuse with UL, CSA, and CE approvals
- Ferrule-end construction for secure mounting in standard fuse holders
- Manufactured to industrial reliability standards for critical automation applications
Technical Specifications
- Rated Current: 4 Amps
- AC Voltage Rating: 600 VAC
- DC Voltage Rating: 300 VDC
- Fuse Class: RK5 (Class R, Rejection-type)
- Element Type: Dual-Element (Time-Delay)
- Interrupting Rating: 200 kA @ 600 VAC; 20 kA @ 300 VDC
- Time Delay: 10 seconds minimum at 500% rated current
- Physical dimensions: 0.81″ diameter × 5″ length (20.57 × 127 mm)
- Weight: 3.2 oz per fuse
- End Type: Ferrule × Ferrule
- Certifications: UL, CSA, CE
Typical Applications
The FRS-R-4 is used extensively in:
- Industrial motor control circuits requiring dual overload and short-circuit protection
- Transformer protection in power distribution panels and switchboards
- Motor starter circuits subject to inrush current and temporary overloads
- General-purpose industrial control equipment where RK5 protection is specified
- HVAC, pump, conveyor, and compressor motor circuits (4A or smaller loads)
Compatibility & Replacements
Compatible With
- Standard Class R (RK5) cartridge fuse holders with ferrule-end receptacles
- Industrial switchgear and motor control panels rated 600VAC/300VDC
- Enclosed fused disconnects and distribution boxes
- Standard industrial fuse blocks and clip-based fuse assemblies
Replaces / Drop-In Replacement For
- Earlier Bussmann Fusetron FRS-R-4 models (same part number retains compatibility)
- Mersen TRS-R 4A RK5 equivalent (verify with system integrator before substituting)
- Littelfuse FLSR 4A fuse (check mechanical fit and electrical characteristics)
Works With
- Class RK5-certified fuse holders and rejection-type clips
- Standard 600VAC industrial control systems and motor starters
- 24VDC logic circuits with 300VDC transient protection
- EtherNet/IP and industrial automation controllers requiring separate branch-circuit fusing
