Littelfuse LLNRK Series POWR-P...
IN STOCK (leaves warehouse same day if ordered before 3pm ET)
$26.07
Littelfuse LLNRK Series POWR-PRO Dual-Element Time-Delay Fuse

Littelfuse LLNRK Series POWR-PRO Dual-Element Time-Delay Fuse

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Model: LLNRK100

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

$26.07
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Littelfuse LLNRK Series POWR-PRO Dual-Element Time-Delay Fuse

The Littelfuse LLNRK Series POWR-PRO fuses are dual-element, time-delay fuses engineered to deliver overload and short-circuit protection for service entrance, main, feeder, and general-purpose branch circuits rated up to 600 amperes, and are available in 100A and 300A models to fit a range of Class H fuse block applications. Rated 250VAC / 125VDC, these fuses are designed as a direct upgrade for existing Class H fuse blocks that currently house lower interrupting-rating Class H one-time or renewable fuses, giving facilities a higher level of protection without replacing the fuse block. Their true dual-element, current-limiting construction is built to handle demanding, high-inrush applications while resisting nuisance opening from routine power surges.

Key Features

  • Model Options: Available in 100A and 300A ratings within the LLNRK Series to match the load and protection needs of the application.
  • Class H Fuse Block Compatible: Installs directly into existing Class H fuse blocks, upgrading systems that use lower interrupting-rating Class H one-time or renewable fuses.
  • Electrical Ratings: Rated 250VAC and 125VDC, with an interrupting rating of 20,000A@125VDC for reliable performance under fault conditions.
  • 300kA Interrupting Rating: Littelfuse self-certifies the LLNRK Series to 300,000 amperes as standard, for higher available short-circuit currents.
  • True Dual-Element Construction: A separate, non-fatiguing, thermally-reversible spring-loaded thermal overload element withstands repeated surges within the rated time delay without needless opening, cutting nuisance downtime.
  • Extremely Current Limiting: Stops damaging short circuits faster than a mechanical device, reducing equipment damage.
  • Reduced System Costs: Current-limiting design often permits less costly downstream equipment, while low resistance reduces power consumption.
  • Time-Delay Opening: Slo-Blo / Time Lag (T) / Time Delay opening characteristic suited to motors, transformers, and other high-inrush loads.
  • Industrial Cartridge Package: Supplied in an industrial cartridge package size for straightforward installation in compatible fuse blocks and holders.

Certifications & Compliance

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

Technical Specifications

  • Voltage Rating: 250VAC/125VDC
  • Configuration: Time-Delay (Slo-Blo)
  • Standards: CSA

Typical Applications

  • Solenoids
  • Fluorescent Lighting Circuits
  • All General-Purpose Circuits
  • Motors and Transformers
  • System Components with High In-Rush Currents
  • Service Entrance, Main, Feeder, and Branch Circuit Protection up to 600A

Why Littelfuse?

Littelfuse backs the LLNRK POWR-PRO Series with true dual-element, current-limiting construction, a self-certified 300kA interrupting rating, and UL and CSA certification—a dependable, code-compliant fuse lineup spanning 100A to 300A for upgrading Class H fuse blocks.

Product Specs

Product Type:
Time-Delay Fuse
Voltage Rating:
250VAC/125VDC
Configuration:
Time-Delay (Slo-Blo)
Listing:
UL Listed
Standards:
CSA
Department:
Electrical
Product Group:
Circuit Protection
Product Subgroup:
Fuses

Littelfuse LLNRK100 – Frequently Asked Questions

1) Can I drop a Littelfuse LLNRK fuse into my existing Class H fuse block?
Yes. The LLNRK POWR-PRO is built to install directly into existing Class H fuse blocks, so you can upgrade a block currently holding lower interrupting-rating Class H one-time or renewable fuses without replacing the block or the holder. It comes in an industrial cartridge package for that reason.
2) Is a 250V fuse like the LLNRK safe to use on a 480V system?
No. The LLNRK is rated 250VAC / 125VDC, and a fuse must be applied at or above the system voltage. For a 480V circuit you need a 600V-class fuse instead. On the DC side, the interrupting rating is 20,000A at 125VDC.
3) Will the LLNRK hold up to motor starting inrush without blowing?
That is what the dual-element design is for. A separate non-fatiguing, thermally reversible spring-loaded thermal overload element takes repeated surges within the rated time delay without opening, so motors, transformers, solenoids, and fluorescent lighting circuits start without nuisance outages. The opening characteristic is time-delay (Slo-Blo / Time Lag T).
4) What interrupting rating does the LLNRK carry for a high available fault current service?
Littelfuse self-certifies the LLNRK Series to 300,000 amperes as standard, which covers services with high available short-circuit current. On DC the rating is 20,000A at 125VDC. The fuse is also extremely current limiting, clearing a short faster than a mechanical device and holding let-through energy down on the equipment behind it.
5) What is the closest time-delay alternative to a Littelfuse LLNRK POWR-PRO fuse?
The nearest time-delay equivalent is the Mersen A2D-R, a Class RK1 time-delay fuse with SmartSpot indication. Both are time-delay designs intended for motor, transformer, and other high-inrush loads. The LLNRK POWR-PRO is rated 250VAC/125VDC and drops into existing Class H fuse blocks, which matters if you are upgrading a block already in service rather than replacing it; the Mersen A2D-R is a Class RK1 fuse and carries a blown-fuse indicator on the body, which some maintenance crews prefer for quick visual troubleshooting.
6) I need a fuse that clears fast instead of riding through inrush - what should I use instead of the LLNRK?
If the circuit has no inrush to tolerate and you want the fastest clearing, use a fast-acting fuse rather than the LLNRK. The Mersen A2K Series is a fast-acting Class RK1 fuse rated 250V, and the Mersen A2K12R in the A6K-R series is also fast-acting Class RK1. The Littelfuse LLNRK is a time-delay (Slo-Blo) fuse with a separate thermal overload element specifically so it will not open on routine surges, which makes it the wrong choice where you want immediate clearing on a non-inrush load such as a purely resistive or electronic circuit.
7) My panel takes Class RK1 fuses - can I order the Littelfuse LLNRK, or do I need a Mersen?
Match the holder. The Littelfuse LLNRK POWR-PRO is built to install directly into existing Class H fuse blocks, which is its intended upgrade path for blocks currently holding Class H one-time or renewable fuses. If your equipment is specified and rejection-prepped for Class RK1, the Mersen A2D-R is a Class RK1 time-delay fuse and the Mersen A2K Series is a Class RK1 fast-acting fuse at 250V. Confirm the class marked on the block before ordering, since rejection features will decide what physically seats.
8) What amp ratings does the LLNRK POWR-PRO fuse come in?
Two ratings: LLNRK100 at 100A and LLNRK300 at 300A. Pick by the load and the protection level of the circuit you are feeding, whether that is a service entrance, main, feeder, or general-purpose branch circuit.
9) Is the Littelfuse LLNRK UL Listed and CSA certified for an inspected installation?
Both. The LLNRK is UL Listed under UL File JDDZ E81895 and CSA Certified under CSA 1422-02 029862, which is normally what an inspector or a spec sheet wants to see on a service entrance or feeder fuse.
10) What is the difference between the Littelfuse LLNRK and a Mersen A2K fast-acting fuse?
Opening characteristic. The LLNRK is a dual-element time-delay (Slo-Blo) fuse, so it rides through motor and transformer inrush. The Mersen Amp-Trap A2K Series is a fast-acting Class RK1 fuse rated 250V, which suits non-inductive loads and is not intended to carry starting surges. If you want time delay from Mersen instead, the A2D-R Class RK1 with SmartSpot indication is the time-delay option.
11) Will a Mersen D0R0 medium voltage fuse work in place of a Littelfuse LLNRK?
No. The Mersen D0R0 Series Amp-Trap is an E-rated medium voltage fuse with ferrule terminals, intended for medium voltage distribution equipment. The Littelfuse LLNRK POWR-PRO is a low voltage fuse rated 250VAC/125VDC for service entrance, main, feeder, and branch circuit protection in Class H fuse blocks. The two are not interchangeable in either direction - voltage class, mounting, and the equipment they go into are all different.
12) Is the Square D PowerLogic energy meter fuse pack a substitute for an LLNRK fuse?
No - it looks like a fuse but serves a completely different job. The Square D PowerLogic Energy Meter Fuse Pack is a set of three 0.5A 600V fuses for protecting the voltage sensing inputs of a PowerLogic energy meter. The Littelfuse LLNRK POWR-PRO is a power fuse offered in 100A and 300A ratings at 250VAC/125VDC for protecting the circuit itself. If you are fusing a meter's potential leads, the Square D pack is the correct item; if you are protecting a feeder or motor circuit, it is the LLNRK.
13) Which time-delay fuse gives maintenance staff a visual indication that it has blown?
The Mersen A2D-R is the one with built-in indication - it is a Class RK1 time-delay fuse with SmartSpot indication, so a technician can identify an opened fuse without pulling and testing it. The Littelfuse LLNRK POWR-PRO is a dual-element time-delay fuse in an industrial cartridge package rated 250VAC/125VDC and is the one to specify when you are upgrading an existing Class H block in place. For facilities standardizing on one approach, decide first whether the block is Class H or Class RK1, then whether indication is worth specifying.
14) Is there a time-delay alternative to the LLNRK with a blown-fuse indicator?
Yes. The Mersen A2D-R Class RK1 time-delay fuse includes SmartSpot indication, so a technician can see at a glance which fuse has opened. The LLNRK gives you the same time-delay characteristic but without an indicator feature.
15) Does upgrading to a current-limiting fuse like the LLNRK let me use cheaper downstream gear?
Often, yes. Because the LLNRK is extremely current limiting, it cuts the fault energy reaching downstream equipment, which can permit less costly downstream components in the design. Its low resistance also reduces power consumption in normal operation.
How fast can I get the Littelfuse LLNRK100 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 LLNRK100 come with a warranty?
Absolutely. The Littelfuse LLNRK100 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 LLNRK100?
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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