Littelfuse LLSRK100ID Class RK...
IN STOCK (leaves warehouse same day if ordered before 3pm ET)
$63.01
Littelfuse LLSRK100ID Class RK1 Time-Delay Fuse, 100A

Littelfuse LLSRK100ID Class RK1 Time-Delay Fuse, 100A

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Model: LLSRK100ID

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

$63.01
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Littelfuse LLSRK100ID Class RK1 Time-Delay Fuse, 100A

The Littelfuse LLSRK100ID from the LLSRK_ID Series is a Class RK1, 100A time-delay (Slo-Blo) fuse built with knife-blade terminals and rated 600VAC/300VDC. It uses patented Indicator™ technology to give instant visual confirmation of a blown fuse, helping maintenance crews cut troubleshooting time and system downtime. Precision-formed short circuit elements and a solid-state overload section combine to protect modern circuits from unexpected electrical faults while resisting the fatigue failures common to spring-loaded designs.

Key Features

  • Ampere Rating: 100A for dependable overcurrent protection in Class RK1 applications.
  • Electrical Rating: 600VAC / 300VDC with an interrupting rating of 20,000A@300VDC for high fault-current environments.
  • Time-Delay Opening: Slo-Blo/Time Lag (T) characteristic reduces nuisance opening and lengthens fuse life under normal cycling and inrush conditions.
  • Knife-Blade Package: Knife-Blade terminal design suited for high-ampacity fuse blocks and disconnects.
  • Blown-Fuse Indicator: Patented Indicator™ window immediately shows when the fuse has opened — if the window is dark, the fuse is open, cutting diagnostic time.
  • Solid-State Overload Section: No moving parts, eliminating the fatigue failures common in spring-loaded overload elements.
  • Precision-Formed Elements: Short circuit elements are precision formed to virtually eliminate component damage from unexpected electrical faults.
  • Reduced Inventory: Broad application coverage lets facilities standardize on fewer fuse types, reducing spare-parts inventory.

Certifications & Compliance

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

Technical Specifications

  • VAC (V): 600
  • VDC (V): 300
  • Ampere Rating (A): 100
  • Interrupting Rating: 20000A@300VDC
  • Opening: Slo-Blo/Time Lag (T)/Time Delay
  • Package Size: Knife-Blade

Typical Applications

  • Motor Control and Branch Circuit Protection
  • Panelboard and Switchboard Overcurrent Protection
  • Industrial Control Panels and Machinery
  • Commercial and Industrial Electrical Distribution Equipment
  • Facilities Seeking Reduced Fuse Inventory and Faster Fault Diagnosis

Why Littelfuse?

Littelfuse engineers the LLSRK_ID Series with a solid-state overload section, precision-formed short circuit elements, and patented Indicator™ blown-fuse technology to deliver dependable, code-compliant overcurrent protection. Backed by UL Listing and CSA Certification, the LLSRK100ID gives electrical professionals a Class RK1, 100A fuse built to reduce downtime, minimize nuisance opening, and stand up to demanding industrial and commercial circuits.

Product Specs

Product Type:
Time-Delay Fuse
Series:
LLSRK_ID
Amperage Rating:
100A
Voltage Rating:
600VAC/300VDC
Configuration:
Time-Delay (Slo-Blo)
Listing:
UL Listed
Standards:
CSA
Department:
Electrical
Product Group:
Circuit Protection
Product Subgroup:
Fuses

Littelfuse LLSRK100ID – Frequently Asked Questions

1) Will a Littelfuse LLSRK100ID fit my existing 100 amp Class R fuse block?
The LLSRK100ID is a Class RK1 fuse with knife-blade terminals, which is the standard package for Class R fuses at 100A. It drops into a 600V Class R rejection fuse block or disconnect sized for 100A knife-blade fuses. Note that Class R rejection hardware accepts Class R fuses but blocks non-rejection Class H/K fuses, so a Class R fuse goes into either style of block, while an older non-rejection fuse will not go into Class R hardware.
2) Can I use the LLSRK100ID on a 480V or 240V system, or only 600V?
Rated 600VAC and 300VDC, so it covers any AC system at or below 600V, including 480V and 240V three-phase. On DC it is limited to 300V, with an interrupting rating of 20,000A at 300VDC. Using a fuse above its voltage rating is not permitted; using it below is normal practice.
3) Is the Littelfuse LLSRK100ID UL Listed and CSA certified for use in an industrial control panel?
Yes, UL Listed under UL JDDZ E81895 and CSA Certified under CSA 1422-02 029862. That covers the documentation most inspectors and panel shops ask for on industrial control panels, panelboards, and switchboard overcurrent protection.
4) Can I use a fast-acting Class RK1 fuse in place of the LLSRK100ID on a motor circuit?
They are not interchangeable in behavior. The LLSRK100ID is a time-delay (Slo-Blo) fuse, which rides through motor inrush without nuisance opening. Mersen's A2K12R, from the A6K-R series, is a Class RK1 fast-acting fuse, and the Amp-Trap A2K series is likewise fast-acting; those clear quickly and are chosen for circuits where inrush is not a factor. Same fuse class and mounting class, different time-current characteristic, so match the characteristic the circuit was designed around.
5) What is the closest cross-brand equivalent to the Littelfuse LLSRK100ID Class RK1 time-delay fuse with a blown-fuse indicator?
The Mersen A2D-R is the nearest counterpart: it is also a Class RK1 time-delay fuse, and it carries SmartSpot indication, the same idea as the patented Indicator window on the LLSRK100ID that shows at a glance when the fuse has opened. The Littelfuse part is rated 600VAC/300VDC at 100A, so confirm the Mersen ampere and voltage rating you order matches the holder and circuit before swapping.
6) How do I tell if a Littelfuse LLSRK100ID has blown without pulling it out and testing it?
It has Littelfuse's patented Indicator window built in. A dark window means the fuse is open. That lets a maintenance tech identify the blown leg of a three-phase set visually at the disconnect instead of pulling all three fuses and ohming them out.
7) Can I standardize my facility's spare fuse stock on the Littelfuse LLSRK_ID series?
That is one of the reasons the series exists. Because a 600V Class RK1 time-delay fuse works on 600V, 480V, and 240V AC circuits and tolerates motor inrush, one fuse type covers motor control, branch circuits, panelboards, switchboards, and machinery panels. That lets you carry fewer part numbers in the crib, stocking by amp rating instead of by fuse class and speed.
8) Is the Mersen D0R0 Amp-Trap fuse a substitute for the LLSRK100ID?
No. The Mersen A055F1D0R0-150E is an E-rated medium voltage fuse with a ferrule terminal, a different class of device for medium voltage circuits. The LLSRK100ID is a Class RK1 low-voltage fuse rated 600VAC/300VDC with knife-blade terminals for high-ampacity fuse blocks and disconnects. Neither the mounting nor the application overlaps.
9) My panel is only 250V - is the Mersen A2K a better fit than the LLSRK100ID?
On voltage, the Mersen Amp-Trap A2K series Class RK1 fuse is rated 250V, while the LLSRK100ID is rated 600VAC/300VDC and can be applied on circuits up to 600VAC. A 600V-rated fuse may be used on a lower-voltage system, but a 250V fuse cannot go the other way. The other difference is the characteristic: the A2K is fast-acting, the LLSRK100ID is time-delay.
10) What exactly do I order, and is this a single fuse or a set?
The part number is LLSRK100ID, a single 100A Class RK1 time-delay fuse. Three-phase gear takes three, so order per pole. By contrast, something like the Square D PowerLogic EMFP3 energy meter fuse pack ships as a set of three 0.5A 600V fuses, which is a metering accessory and not a substitute for a 100A branch circuit fuse.
11) Will the indicator mechanism on this fuse wear out or fail over time like spring-loaded designs?
The overload section is solid state with no moving parts, which is what eliminates the fatigue failures that spring-loaded overload elements are prone to. The short circuit elements are precision formed to limit collateral damage when a fault hits.
12) Will a Square D PowerLogic meter fuse pack work where the LLSRK100ID goes?
No. The Square D EMFP3 is a set of three 0.5A 600V fuses for protecting energy meter inputs - a control-circuit sized device. The LLSRK100ID is a 100A Class RK1 knife-blade fuse for branch circuit, motor control, and panelboard overcurrent protection. They share a voltage class only; the ampere rating and the job are entirely different.
How fast can I get the Littelfuse LLSRK100ID 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 LLSRK100ID come with a warranty?
Absolutely. The Littelfuse LLSRK100ID 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 LLSRK100ID?
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
Why buy the Littelfuse LLSRK100ID from ZenSupply?
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