Overview
The Bussmann FRS-R 6.25 is a Class RK5 dual-element, time-delay fuse engineered for industrial and commercial branch-circuit protection. Rated 600 Vac/300 Vdc, this fuse combines current-limiting technology with time-delay characteristics, delivering selective protection without nuisance interruptions. Fusetron FRS-R fuses are manufactured to strict UL standards and offer reliable overcurrent protection across a broad range of equipment and systems.
Key Features
- Dual-element, time-delay construction — Delivers 10 seconds (minimum) of time-delay at 500% of rated current (8 seconds for 1/10-30A sizes), allowing inrush currents to settle without nuisance blows
- Class RK5 current-limiting protection — Interrupting rating of 200 kA at 600 Vac and 20 kA at 300 Vdc, limiting let-through current in short-circuit events
- Non-indicating design — No blown fuse indication; ideal for panel mounting with visual inspection
- UL and CSA certification — Meets UL Std. 248-12 and CSA C22.2 No. 248.12 Class RK5 requirements
- Ferrule-end construction for secure grip in standard Class R fuse holders
- Made in the USA with robust ceramic body and copper-alloy ferrules
Technical Specifications
The following specifications apply to the FRS-R 6.25 model:
- Ampere Rating: 6.25 A
- Voltage Rating: 600 Vac / 300 Vdc
- Class: RK5 (Class R rejection-type)
- Fuse Type: Dual-element, time-delay
- Time-Delay Response: 10 seconds minimum at 500% rated current
- Interrupting Rating: 200 kA RMS Sym (Vac) / 20 kA (Vdc)
- Catalog Format: FRS-R-6.25 or FRS-R-6¼
- Body Material: Ceramic with copper-alloy ferrules
- Connection Type: Ferrule-end, rejection-type
- Length (1/10–30A): 5.0″ nominal
- Body Diameter: 0.81″ nominal
- Weight (per fuse): Approximately 0.14 lb
Typical Applications
The Bussmann FRS-R 6.25 time-delay fuse is suited for:
- General-purpose branch-circuit protection in industrial control panels
- Motor circuit protection (where time delay prevents nuisance trips during soft-start or VFD ramp-up)
- Transformer secondary protection
- Equipment interior power supplies and distribution systems
- Commercial HVAC, lighting, and facility electrical systems
- Machine tool and manufacturing equipment
Compatibility & Replacements
Compatible With
- Standard Class R fuse holders and blocks
- Industrial control panels rated 600 Vac service
- Equipment accepting ferrule-end, rejection-type Class RK5 fuses
- Systems designed for dual-element, time-delay protection
- UL-listed switchboards, panelboards, and disconnect switches
Replaces / Drop-In Replacement For
The FRS-R 6.25 directly replaces:
- Bussmann FRS-R-6.25 (all manufacturer revisions)
- Bussmann FRS-R-6¼ (fractional amperage equivalent)
- Legacy or superseded FRS-R 6-amp units in 6.25 A applications
Caution: Verify exact amperage and voltage requirements before installation. Do not interchange with FRS-R units of different ampere ratings.
Works With
- Class RK5 fuse blocks and rejection-type holders
- Standard industrial control cabinets and distribution panels
- Motor starters and VFDs (as upstream branch protection)
- Industrial automation systems requiring selective overcurrent protection
- Equipment certified to UL 508 and UL 844 standards
