Overview
The Bussmann FRS-R-70 is a Class RK5 Fusetron dual-element, time-delay cartridge fuse engineered for reliable overload and short-circuit protection in industrial, commercial, and agricultural electrical systems. This fuse combines time-delay characteristics with current-limiting performance, making it ideal for circuits subject to motor startup inrush currents and temporary surge conditions. The FRS-R-70 delivers 200 kA interrupting rating at 600 Vac and 20 kA at 300 Vdc, ensuring robust protection for machinery disconnects, motor control centers, and power distribution equipment.
Key Features
- Dual-Element, Time-Delay Construction — Delivers 10 seconds (minimum) of time-delay at 500% of rated current, allowing motor startup surges while blocking sustained overloads
- Current-Limiting Performance — Opens in as little as 0.004 second if the fuse experiences short-circuit conditions, minimizing equipment damage
- Class RK5 Rating — Dual-element, time-delay construction provides energy efficient advanced protection with rejection-type design compatible with Class H, K, or R fuse blocks
- High Interrupting Rating — 200 kA at 600 Vac and 20 kA at 300 Vdc for superior fault current handling
- Motor Protection Optimized — Helps protect motors from burnout caused by overloads or single-phasing; the time-delay feature allows the initial startup current surge for typical motors to pass, but opens prior to motor burnout when longer, dangerous overloads are present
- Selective Coordination — 2:1 selective coordination ratio within the RK5 fuse family prevents electrical shutdowns from extending beyond the failed circuit
Technical Specifications
- Amperage Rating: 70 A
- Voltage Rating: 600 Vac / 300 Vdc
- Fuse Class: RK5
- Construction Type: Dual-Element, Time-Delay
- Current-Limiting: Yes
- Interrupting Rating: 200 kA @ 600 Vac RMS Sym. / 20 kA @ 300 Vdc
- Time-Delay Response: 10 seconds minimum at 500% rated current
- Short-Circuit Response: 0.004 second maximum
- Body Diameter: 1.11 inches
- Body Length: 7.88 inches
- Terminal Type: Knife Blade (Rejection-Type)
- Element Material: Fiberglass
- Indication: Non-Indicating
- UL Listing: cULus Listed
Typical Applications
- Motor branch circuits and motor overload protection in pump, compressor, and fan applications
- Combination motor starters and motor control centers
- Machinery disconnects and power panelboards
- Industrial process control equipment subject to inductive surge currents
- Agricultural equipment and HVAC systems where time-delay protection is required
- Any circuit where selective coordination and current limiting are required
Compatibility & Replacements
Compatible With
- Class H, Class K, and Class R fuse blocks and holders
- Knife-blade terminal equipment rated for 600 Vac or 300 Vdc
- Motor control centers and combination starters
- Machinery disconnect switches
- Industrial power distribution panels
Replaces / Drop-In Replacement For
- Cooper Bussmann FRS-R-70 (legacy branding)
- Interchangeable with other Class RK5 70A fuses from the FRS-R series
- Verify compatibility with your specific equipment before ordering
Works With
- Eaton Bussmann and Cooper Bussmann branch circuit protection systems
- Standard Class R rejection-type fuse blocks and cartridge holders
- Switchboards, panelboards, and motor control centers with RK5 fuse cavities
- Any industrial electrical system requiring UL-listed Class RK5 protection
