Littelfuse FLSR Series Class R...
IN STOCK (leaves warehouse same day if ordered before 3pm ET)
$56.97
Littelfuse FLSR Series Class RK5 Dual-Element Time-Delay Fuse, 600VAC/300VDC

Littelfuse FLSR Series Class RK5 Dual-Element Time-Delay Fuse, 600VAC/300VDC

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Model: FLSR035

In Stock (leaves warehouse same day if ordered before 3pm ET)

$56.97
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Littelfuse FLSR Series Class RK5 Dual-Element Time-Delay Fuse, 600VAC/300VDC

The Littelfuse FLSR Series is a UL Class RK5 dual-element time-delay fuse line rated 600VAC/300VDC, built in a knife-blade package for use in fused disconnects and switches. Available in ampere ratings from 1A to 450A across 24 selectable options, the FLSR series is one of the most widely specified dual-element time-delay fuse families on the market, delivering dependable overcurrent protection for a broad range of circuits, especially those containing motors. Automated, precision manufactured and assembled construction ensures accurate, consistent response to overloads and short circuits, while the time-delay characteristic lets these fuses ride through normal motor inrush and starting currents without nuisance opening.

Key Features

  • Ampere Rating Range: Available from 1A to 450A across 24 amperage options to match a wide range of circuit and motor protection needs.
  • Class RK5 Dual-Element Design: Slo-Blo/Time Lag/Time Delay opening characteristic provides excellent protection for motor and general-purpose circuits.
  • Voltage Rating: 600VAC and 300VDC rating shared across the FLSR series.
  • Knife-Blade Package: Knife-blade terminal configuration for secure engagement in compatible fuse holders and disconnect switches.
  • High Interrupting Capacity: Reliable interruption of overcurrents up to 200,000 amperes A.I.R., with a 20,000A @ 300VDC interrupting rating.
  • Fast Short-Circuit Response: Faster-acting short-circuit protection than any non-current-limiting mechanical protective device.
  • Precision Manufacturing: Automated, precision manufactured and assembled parts ensure accurate, consistent response to overloads and short circuits.
  • Broad Circuit Compatibility: Suitable for service entrance switches, switchboard main and feeder switches, and individual fused combination motor controllers.

Certifications & Compliance

  • UL Listed, Class RK5 (UL JDDZ E81895)
  • CSA Certified (CSA 1422-02 029862)

Technical Specifications

  • Refer to manufacturer documentation for complete technical specifications.

Typical Applications

  • Service Entrance Switches
  • Switchboard Main and Feeder Switches
  • Protection of Fully-Rated Panelboards and Loadcenters
  • Industrial Control Panels
  • Individual Fused Combination Motor Controllers
  • Motor Control Center Mains and Motor Branch Circuits

Why Littelfuse?

Littelfuse FLSR series fuses are UL Class RK5 listed and CSA certified, reflecting the precision manufacturing and consistent overcurrent response professionals rely on for code-compliant electrical work. With a shared 600VAC/300VDC rating, ampere options spanning 1A to 450A, and interrupting capability up to 200,000 amperes A.I.R., the FLSR series delivers dependable, faster-than-mechanical short-circuit protection for demanding motor control, panelboard, and distribution applications where reliability and accurate overcurrent response are essential.

Product Specs

Product Type:
Fuse
Series:
FLSR
Voltage Rating:
600VAC
Configuration:
Class RK5 Dual-Element Time-Delay
Listing:
UL Listed
Standards:
CSA Certified
Department:
Electrical
Product Group:
Wiring Devices

Littelfuse FLSR035 – Frequently Asked Questions

1) Will a Littelfuse FLSR fuse hold on motor starting inrush without nuisance blowing?
That is what the dual-element time-delay design is for. The FLSR is a Class RK5 dual-element time-delay (Slo-Blo) fuse, so it rides through normal motor inrush and starting current while still opening on a sustained overload. It is used in individual fused combination motor controllers and motor control center mains and motor branch circuits. If you need a fuse that clears fast on every surge, a time-delay fuse is the wrong choice.
2) Will a knife-blade FLSR fuse fit my fuse clips, or do I need ferrule ends?
The FLSR series is built in a knife-blade package, which seats in knife-blade fuse clips in disconnects and switches. Ferrule (cylindrical cap) holders will not accept it. Class R clips are also rejection style, so confirm your switch is Class R rated before ordering.
3) Is the FLSR fuse rated high enough for a service with high available fault current?
It interrupts up to 200,000 amperes A.I.R. on AC, and 20,000A at 300VDC. That covers service entrance switches, switchboard main and feeder switches, and fully-rated panelboards and loadcenters where available fault current is high.
4) What is the difference between the Littelfuse FLSR and the Mersen A2D-R time-delay fuse?
Both are time-delay fuses for motor and feeder circuits, but they are different UL classes. The Littelfuse FLSR is a Class RK5 dual-element time-delay fuse rated 600VAC/300VDC. The Mersen A2D-R is a Class RK1 time-delay fuse, and Mersen adds SmartSpot blown-fuse indication to that line. Class RK1 and Class RK5 fuses share the same rejection-style dimensions for a given amp rating and voltage, so they fit the same rejection holders, but they have different let-through energy characteristics - if a drawing or equipment label calls out RK1 specifically, the FLSR is not a drop-in for it.
5) Can a Littelfuse FLSR replace a medium-voltage fuse in a transformer primary?
No. The FLSR Series is a 600VAC/300VDC low-voltage Class RK5 fuse in a knife-blade package for fused disconnects and switches. Medium-voltage transformer and feeder protection uses a different family entirely, such as the Mersen D0R0 Series Amp-Trap E-rated medium voltage fuse with ferrule terminals. E-rated medium-voltage fuses and Class RK5 fuses are not interchangeable in either direction.
6) My disconnect is a 250V circuit - is the FLSR the right fuse or is there a 250V option?
Every amp rating in the Littelfuse FLSR Series shares the 600VAC/300VDC rating, so there is no 250V version of the FLSR; a 600V fuse may be applied on a lower-voltage circuit but the physical dimensions are the 600V case size and will not fit a 250V fuse clip. For a true 250V class-R time-delay fuse, the Mersen A2D-R is rated 250VAC/250VDC. Confirm which case size your switch is built for before ordering either.
7) What amp ratings does the Littelfuse FLSR fuse come in?
Twenty-four ratings span 1A up to 450A. The low end covers control and instrument circuits (1A, 1.5A, 1.6A, 2A, 3A, 3.2A, 3.5A, 4A, 4.5A, 6A, 10A), the middle covers typical branch and feeder work (20A, 25A, 30A, 40A, 50A, 60A, 70A, 80A, 90A), and the large sizes handle mains and service equipment (125A, 150A, 175A, 450A). Part numbers follow the rating, so a 30A is FLSR030 and a 150A is FLSR150.
8) Are Littelfuse FLSR fuses UL Listed and CSA certified for code work?
Yes. The FLSR series is UL Listed as Class RK5 under UL JDDZ E81895 and CSA Certified under CSA 1422-02 029862.
9) I need a blown-fuse indicator on the fuse itself - does the Littelfuse FLSR have one?
The FLSR Series is a Class RK5 dual-element time-delay fuse in a knife-blade package without an integral indicator feature called out. If visual blown-fuse indication is what you are after, the Mersen A2D-R Class RK1 time-delay fuse carries SmartSpot indication, and the 400A A2D400R is the same Class RK1 construction. Note that moving to the A2D-R also moves you from Class RK5 to Class RK1.
10) I need small fuses for a power meter - is the 1A FLSR the right part?
The FLSR Series does go down to 1A (FLSR001) and 1.5A, but these are knife-blade Class RK5 fuses sized for fused disconnects and switches, not for the small fuse blocks inside metering. For revenue and power metering, a purpose-built kit such as the Square D PowerLogic energy meter fuse pack, a set of three 0.5A 600V fuses, matches that application. Check the meter's fuse holder style before substituting.
11) I need a 400A class-R time-delay fuse - does the FLSR cover that?
The Littelfuse FLSR Series runs from 1A to 450A, and the top listed rating is the 450A FLSR450, so the family spans 400A duty but the discrete 400A step is not among the FLSR ratings carried. A dedicated 400A class-R time-delay fuse is the Mersen A2D400R, which is Class RK1 rather than Class RK5. Confirm which class your equipment label permits before choosing.
12) Where do I find the time-current curves and physical dimensions for the FLSR fuse?
Littelfuse publishes the FLSR series spec sheet with the full electrical data, and it is linked on the product record under PDF: Spec Sheet. Use it for time-current characteristics and body dimensions when you are coordinating with an upstream device.
How fast can I get the Littelfuse FLSR035 delivered?
Most orders ship the same day from our distribution partners, with quick delivery throughout the continental U.S. Need it urgently? Contact Us for expedited shipping options.
Can I return it if it doesn’t work for me?
Yes—ZenSupply offers a hassle-free return policy. If the product isn’t the right fit, reach out to our support team for a return authorization or setup a return by following our return instructions.
Does the Littelfuse FLSR035 come with a warranty?
Absolutely. The Littelfuse FLSR035 is backed by a manufacturer’s warranty. For full warranty terms, check the product documentation or Contact Us.
How do I get technical support or installation help for the Littelfuse FLSR035?
You can call, text, or email our expert support team for fast answers. We’re here to help with product selection, installation tips, and troubleshooting. Contact Us
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