Littelfuse FLNR_ID Indicator S...
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Littelfuse FLNR_ID Indicator Series Class RK5 Time-Delay Fuse, 250VAC/125VDC

Littelfuse FLNR_ID Indicator Series Class RK5 Time-Delay Fuse, 250VAC/125VDC

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Model: FLNR040ID

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

$10.04
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Littelfuse FLNR_ID Indicator Series Class RK5 Time-Delay Fuse, 250VAC/125VDC

The Littelfuse FLNR_ID Indicator Series is a Class RK5 dual-element time-delay fuse family rated 250VAC / 125VDC with an interrupting rating of 300,000A@250VDC, available in 40A, 45A, 60A, and 125A ratings to cover a wide range of branch-circuit and equipment protection needs. Each fuse uses a patented solid-state design to deliver visual blown-fuse indication at a glance, helping electricians and maintenance teams pinpoint an open fuse without testing. The Slo-Blo/Time Lag (T) time-delay characteristic reduces nuisance opening while maintaining reliable overload and short-circuit protection for industrial and commercial electrical systems, from motor controllers to distribution panelboards.

Key Features

  • Amp Rating Range: Available in 40A, 45A, 60A, and 125A ratings for branch-circuit and equipment protection.
  • Voltage Rating: 250VAC / 125VDC for use across AC and DC industrial circuits.
  • Interrupting Rating: 300,000A@250VDC for high fault-current withstand.
  • Time-Delay Opening: Slo-Blo/Time Lag (T)/Time Delay characteristic reduces nuisance opening and extends fuse life.
  • Visual Blown-Fuse Indication: The Indicator window shows an open fuse at a glance, with power on or off, so no fuse testing or second-guessing is required.
  • Dual-Element Solid-State Design: Patented construction delivers maximum reliability and superior overload and short-circuit protection to help reduce equipment damage.
  • Reduced Down-Time: A glance at the indicating window pinpoints an open fuse immediately, letting operators request the proper replacement without guesswork.
  • Package Size: Industrial Cartridge format.

Certifications & Compliance

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

Technical Specifications

  • Refer to manufacturer documentation for complete specifications.

Typical Applications

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

Why Littelfuse?

Littelfuse engineers the FLNR_ID Indicator Series with a dual-element, solid-state design that combines superior overload and time-delay performance with built-in visual blown-fuse indication across the full 40A-125A rating range. For electricians and facility teams protecting panelboards, motor controllers, and industrial control panels, this combination of UL Listed and CSA Certified reliability with reduced down-time and fewer nuisance openings makes Littelfuse a dependable choice for code-compliant circuit protection.

Product Specs

Product Type:
Time-Delay Fuse
Series:
FLNR_ID Indicator Series
Voltage Rating:
250VAC / 125VDC
Amperage Rating:
40A - 125A
Listing:
UL Listed
Standards:
CSA Certified
Grade:
Class RK5
Department:
Electrical
Product Group:
Circuit Protection
Product Subgroup:
Fuses

Littelfuse FLNR040ID – Frequently Asked Questions

1) Can a Littelfuse FLNR_ID fuse be used on a 480V circuit?
No. The FLNR_ID Indicator Series is rated 250VAC / 125VDC, so it only belongs on circuits at or below those voltages. On a 480V system you need a 600V class fuse instead. Putting a 250V fuse on a 480V circuit is a safety problem, not just a spec mismatch.
2) Will a Class RK5 fuse drop into a fuse block sized for Class RK1 or Class H fuses?
Class RK5 and Class RK1 share the same R-class dimensions and rejection feature, so the FLNR_ID fits any holder built for R-class fuses of the same amp rating and 250V class. What differs is performance: RK1 fuses let through less energy on a fault, so if your equipment label or drawing specifically calls for RK1, substitute a Class RK1 part such as the Mersen A2D-R rather than this RK5.
3) Why choose a time-delay fuse for a motor circuit instead of a fast-acting one?
Motors pull several times full-load current on start. The FLNR_ID uses a dual-element Slo-Blo / Time Lag (T) characteristic that rides through that inrush without opening, while still clearing overloads and short circuits. That is why it is used on fused combination motor controllers and motor control center mains and branches. A fast-acting fuse on the same circuit tends to open every time the motor starts.
4) I need a time-delay fuse above 125A - what can I use instead of the FLNR_ID series?
The Littelfuse FLNR_ID Indicator Series covers 40A through 125A, so for a larger feeder you would step to a higher-amp fuse such as the Mersen A2D400R, a Class RK1 400A time-delay fuse with SmartSpot indication. Note the class change: the FLNR_ID is Class RK5, while the A2D400R is Class RK1, so confirm which class the switch or panelboard is rated for before ordering.
5) What is the difference between the Littelfuse FLNR_ID fuse and the Mersen A2D-R with SmartSpot indication?
Both are time-delay cartridge fuses with a built-in blown-fuse indicator, but they are different UL fuse classes. The Littelfuse FLNR_ID Indicator Series is a Class RK5 dual-element time-delay fuse rated 250VAC/125VDC, offered in 40A, 45A, 60A and 125A. The Mersen A2D-R is a Class RK1 time-delay fuse rated 250VAC/250VDC with SmartSpot indication. Class RK1 and Class RK5 differ in their let-through current limitation, so if a panel schedule or equipment label calls out one class specifically, match that class rather than swapping between them.
6) Which indicating time-delay fuse should I choose for a 250VDC circuit?
For DC duty check the DC rating rather than the AC one. The Littelfuse FLNR_ID Indicator Series is rated 250VAC/125VDC, so it suits DC circuits up to 125VDC. The Mersen A2D-R Class RK1 time-delay fuse with SmartSpot indication is rated 250VAC/250VDC, which covers a 250VDC circuit. Both give visual blown-fuse indication, so the decision comes down to the DC voltage present and the fuse class the equipment requires.
7) What amp ratings does the Littelfuse FLNR_ID indicating fuse come in?
Four ratings: 40A (FLNR040ID), 45A (FLNR045ID), 60A (FLNR060ID), and 125A (FLNR125ID). If your panel or motor controller calls for something between those, such as a 30A or 100A, you are looking at a different part in the FLNR family.
8) What is the interrupting rating on the Littelfuse FLNR_ID fuse?
300,000A@250VDC. That covers service entrance switches, switchboard main and feeder switches, and fully-rated panelboards and loadcenters where available fault current is high.
9) Is the Littelfuse FLNR_ID fuse acceptable for a Canadian installation?
It is CSA Certified (1422-02 029862) as well as UL Listed under file E81895, so it carries the marks an inspector looks for on both sides of the border.
10) Can I use a Mersen Amp-Trap medium voltage fuse in place of a Littelfuse FLNR_ID?
No. The Littelfuse FLNR_ID Indicator Series is a 250VAC/125VDC Class RK5 industrial cartridge fuse for branch-circuit and equipment protection in panelboards and motor controllers. The Mersen A055F1D0R0-150E is an Amp-Trap E-Rated medium voltage fuse with a ferrule terminal, intended for medium voltage applications such as transformer primary protection. They are not interchangeable in either direction.
11) What form factor is the FLNR_ID fuse, ferrule or blade?
Industrial Cartridge format. Within the 40A to 125A range covered here, be aware that R-class cartridge fuses change from ferrule to knife-blade ends as amperage climbs, so match the fuse clip style in your disconnect to the rating you are ordering.
How fast can I get the Littelfuse FLNR040ID 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 FLNR040ID come with a warranty?
Absolutely. The Littelfuse FLNR040ID 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 FLNR040ID?
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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