Littelfuse JLS100 Class J Fast...
IN STOCK (leaves warehouse same day if ordered before 3pm ET)
$67.64
Littelfuse JLS100 Class J Fast-Acting Fuse, 600V 100A

Littelfuse JLS100 Class J Fast-Acting Fuse, 600V 100A

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Model: JLS100

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

$67.64
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Littelfuse JLS100 Class J Fast-Acting Fuse, 600V 100A

The Littelfuse JLS100 is a Class J fast-acting fuse engineered for space-saving overload and short-circuit protection in non-inductive load circuits. Rated 600VAC at 100A with a 200,000A interrupting rating, this knife-blade fuse delivers an extremely current-limiting design that stops damaging short-circuit current faster than any mechanical protective device. Because JLS fuses are optimized for non-inductive loads, motor and other inductive-load applications require an increased ampere rating to prevent nuisance opening on inrush current — for full protection in such circuits, Littelfuse recommends its POWR-PRO™ JTD series time-delay fuses. UL Listed and CSA Certified, the JLS100 is built for dependable overcurrent protection in commercial and industrial power distribution equipment.

Key Features

  • Voltage & Ampere Rating: Rated 600VAC at 100A for reliable circuit protection.
  • Interrupting Rating: 200,000 A.I.R. at 600VAC provides reliable interruption of overcurrents up to 200,000 amperes and minimizes the need for short-circuit calculations.
  • Fast-Acting Opening (F): Delivers fast-acting protection to equipment containing surge-sensitive, solid-state components such as variable speed drives and rectifiers.
  • Extremely Current-Limiting Design: Stops damaging short-circuit current faster than any mechanical protective device, reducing equipment damage caused by heating and magnetic effects.
  • Space-Saving Knife-Blade Package: Offers characteristics similar to KLNR/KLSR fast-acting Class RK1 fuses in a much smaller footprint.
  • Economical Standardization: Extremely current-limiting design permits use of readily available, less costly equipment, and standardizing on 600V JLS fuses with Class J fuse blocks simplifies manufacturing and reduces inventory for dual-voltage devices.

Certifications & Compliance

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

Technical Specifications

  • VAC (V): 600
  • Ampere Rating (A): 100

Typical Applications

  • Resistive Loads, such as Resistance Electric Heat
  • Equipment Containing Solid-State Devices, such as Variable Speed Drives and Rectifiers
  • General Purpose Circuits with Little or No Motor Load
  • Commercial and Industrial Power Distribution Equipment
  • Dual-Voltage Equipment Standardized on Class J Fuse Blocks

Why Littelfuse?

Littelfuse JLS Series fuses pair an extremely current-limiting, fast-acting design with a 200,000A interrupting rating to deliver dependable, code-compliant overcurrent protection in a compact knife-blade package. Backed by UL and CSA certification, the JLS100 helps reduce equipment damage from short-circuit heating and magnetic effects while simplifying inventory for professionals standardizing on Class J fuse protection across commercial and industrial installations.

Product Specs

Product Type:
Fuse
Series:
JLS Series
Voltage Rating:
600V
Amperage Rating:
100A
Configuration:
Knife-Blade
Listing:
UL Listed
Standards:
CSA Certified
Department:
Electrical
Product Group:
Wiring Devices

Littelfuse JLS100 – Frequently Asked Questions

1) Can I use a Littelfuse JLS100 to protect a motor circuit?
Not at its nameplate rating. The JLS Series is optimized for non-inductive loads, so motor and other inductive-load circuits need an increased ampere rating to avoid nuisance opening on inrush. For full motor protection Littelfuse points to its POWR-PRO JTD time-delay Class J fuses instead. Keep the JLS100 on resistive loads, general purpose circuits with little or no motor load, and solid-state equipment like variable speed drives and rectifiers.
2) Will a JLS100 fit a Class RK1 fuse holder like the one my KLNR fuse sits in?
No. The JLS100 is a Class J knife-blade fuse and Class J has its own dimensions and fuse blocks, so it will not drop into an RK1 holder. It does give characteristics similar to KLNR/KLSR fast-acting Class RK1 fuses in a much smaller footprint, which is why Class J is popular for tight gear, but the block has to be a Class J block.
3) Does the JLS100 have enough interrupting capacity for my service with high available fault current?
The interrupting rating is 200,000 amperes at 600VAC, which covers essentially any available fault current in commercial and industrial distribution and minimizes the need for short-circuit calculations. The extremely current-limiting design clears short-circuit current faster than a mechanical protective device, which limits the heating and magnetic damage passed to downstream equipment.
4) Fast-acting or time-delay Class J fuse for a variable speed drive?
Fast-acting is the one you want ahead of surge-sensitive solid-state equipment. The JLS100 carries the fast-acting (F) opening characteristic specifically for gear containing solid-state components such as variable speed drives and rectifiers, where a slower-clearing fuse lets too much energy through the semiconductors. Save the time-delay Class J (JTD) for motor starters and other inductive loads.
5) The JLS100 keeps opening on motor inrush - what fuse should I use for an inductive load instead?
The Littelfuse JLS100 is a Class J fast-acting fuse rated 600V at 100A, and fast-acting Class J is optimized for non-inductive loads, so motor circuits either need an increased ampere rating or a time-delay fuse. Littelfuse points those applications to its POWR-PRO JTD time-delay series. A time-delay alternative in a different class is the Mersen A2D-R, a Class RK1 time-delay fuse with SmartSpot indication, which rides through starting inrush rather than clearing on it. Confirm the fuse block or holder accepts the class you choose - Class J and Class RK1 use different mountings.
6) Can I drop a Mersen A2D-R into the same holder as a Littelfuse JLS100?
No. The Littelfuse JLS100 is a Class J fuse in a knife-blade configuration rated 600V, 100A, and Class J dimensions are deliberately unique so only Class J fuses fit a Class J block. The Mersen A2D-R is a Class RK1 time-delay fuse, a different class with different body and blade dimensions; the A2D-R at 250VAC/250VDC is also a lower voltage class than the 600V JLS100. If you are standardized on Class J blocks, stay with Class J fuses.
7) Is the Littelfuse JLS100 rated for a 480V three-phase panel?
Yes. It is rated 600VAC, so it covers 480V and 240V systems as well. Standardizing on the 600V JLS fuse with Class J blocks is how Littelfuse suggests handling dual-voltage equipment, since one fuse and one block cover both voltages and cuts the number of part numbers you stock.
8) Is the Littelfuse JLS100 UL Listed and CSA approved for an inspected installation?
Yes, both. It is UL Listed under UL JDDZ E81895 and CSA Certified under CSA 1422-02 029862. Those are the markings an inspector or a spec-driven MRO buyer will be looking for on a Class J fuse.
9) What else could I use if my equipment is set up for Class RK1 fuses instead of Class J?
For an RK1 holder, look at the Mersen Amp-Trap 2000 A2D-R Class RK1 time-delay fuses, including the A2D400R at 400A with SmartSpot blown-fuse indication. Those are time-delay rather than fast-acting, so they suit motor and transformer inrush; they are not a substitute for the fast-acting JLS100 ahead of solid-state drives.
10) I need the same fast-acting protection at a higher amperage than 100A - what are my options?
The Littelfuse JLS100 covers 100A at 600V in the JLS series, so larger JLS ampere ratings are the direct path for staying on the same Class J blocks. If the circuit is a motor or other inductive load at higher current, the Mersen A2D400R is a 400A Class RK1 time-delay fuse, though moving to Class RK1 means a different fuse block and a time-delay rather than fast-acting curve. Match the class to the holder already installed before sizing up.
11) Is a Mersen E-rated medium voltage fuse an alternative to the JLS100?
No - they protect entirely different systems. The Littelfuse JLS100 is a 600V, 100A Class J fuse for low-voltage commercial and industrial power distribution, UL Listed and CSA Certified. The Mersen A055F1D0R0-150E is an Amp-Trap E-rated medium voltage fuse with ferrule terminals, intended for medium voltage transformer and feeder protection, not 600V branch circuits. Neither will fit or function in the other's equipment.
12) My meter has 600V fuses in it - is the JLS100 the right replacement?
Almost certainly not. Metering circuits use small ampere ratings for potential-transformer leads, not 100A branch protection. The Square D PowerLogic energy meter fuse pack, for example, is a set of three 0.5A 600V fuses. The Littelfuse JLS100 shares the 600V class but is a 100A knife-blade Class J fuse for power distribution equipment. Use the meter manufacturer's specified fuse for metering inputs and reserve the JLS100 for the feeder or branch it is sized for.
How fast can I get the Littelfuse JLS100 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 JLS100 come with a warranty?
Absolutely. The Littelfuse JLS100 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 JLS100?
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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