Mersen UltraSafe Class J Fuse ...
IN STOCK (leaves warehouse same day if ordered before 3pm ET)
$137.44
Mersen UltraSafe Class J Fuse Holder, DIN Rail Mount, LED Indicator

Mersen UltraSafe Class J Fuse Holder, DIN Rail Mount, LED Indicator

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Model: US3J1I

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

$137.44
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Mersen US3J3I UltraSafe Class J Fuse Holder, 3-Pole, 600VAC/600VDC 30A, IP65

The Mersen US3J3I UltraSafe Class J Fuse Holder delivers reliable circuit protection for demanding industrial and commercial applications. This 3-pole unit is rated 600VAC/600VDC at 30A for Class J fuses, with integrated LED indication for visual fuse-status monitoring and an IP65-rated polyamide housing for durability in harsh environments. Backed by a 200 kA short circuit current rating and DIN rail mounting, it combines safety, performance, and easy maintenance in one compact package.

Key Features

  • Dual Voltage Rating: 600VAC/600VDC compatibility supports both AC and DC systems for broad application flexibility.
  • 30A Class J Fuse Capacity: Handles substantial current loads with precise overcurrent protection using Class J, clip-in fuses.
  • LED Indication System: Provides instant visual confirmation of fuse status, reducing troubleshooting time.
  • IP65 Environmental Protection: Sealed polyamide construction resists dust ingress and water jets for reliable outdoor and industrial use.
  • 200 kA Short Circuit Current Rating: Exceptional fault current handling ensures system protection under extreme conditions.
  • DIN Rail Mounting: Standard industrial mounting enables quick installation and easy panel integration.
  • Durable Construction: High-performance polyamide insulating material provides excellent electrical isolation and mechanical durability.
  • Wiring Range: Accepts #2 to 14 AWG conductors, torqued to 35 lb-in for a secure termination.

Certifications & Compliance

  • RoHS Compliant
  • IP65 Rated Enclosure

Technical Specifications

  • Indication System: Yes
  • Indication System Type: LED
  • Rohs Compliant: Yes
  • Fuse Class: Class J
  • Number Of Poles: 3-Pole
  • Ampere Rating: 30 A
  • Rated Voltage AC/DC: 600 V
  • Body Insulating Material: Polyamide
  • Installation Mounting: DIN Rail
  • Fuse Installation Method: Clip-in
  • Short Circuit Current Rating (SCCR): 200 kA
  • Wiring Range: #2 to 14 AWG
  • Torque Rating: 35 lb-in
  • Product Dimensions: 4.49 in L x 3.84 in W x 3.15 in H
  • Product Weight: 1.43 lb

Typical Applications

  • Industrial Control Panels and Motor Control Centers
  • Commercial HVAC and Building Automation Systems
  • Manufacturing Equipment and Process Control
  • Power Distribution and Electrical Substations
  • Renewable Energy and Solar Power Systems
  • Marine and Offshore Electrical Installations

Why Mersen?

Mersen UltraSafe fuse holders are engineered for dependable circuit protection, backed by RoHS compliance and a rugged IP65 polyamide housing built for long-term performance. The combination of dual 600VAC/600VDC voltage capability, LED fuse-status indication, and a 200 kA short circuit current rating makes this Class J fuse holder a dependable, code-compliant choice for professional electrical installations.

Manufacturer Resources

Mersen Product Catalog

Product Specs

Product Group:
Circuit Protection
Installation Mounting:
DIN Rail
Indication System Type:
LED
Indication System:
Yes
Fuse Class:
Class J
Fuse Installation Method:
Clip-in
Department:
Electrical
Product Type:
Fuse Holder
Product Subgroup:
Fuse Holders & Blocks

Mersen US3J1I – Frequently Asked Questions

1) Will the Mersen UltraSafe fuse holder accept my Class J fuses, and how do they go in?
It takes Class J fuses only, and they clip in rather than screwing down. Class J bodies are dimensionally unique, so a Class R, CC, or T fuse won't seat in these clips. The US3J3I version is rated 600VAC/600VDC at 30A, so the fuse you drop in has to be within that rating.
2) What is the difference between the Mersen US3J and US6J UltraSafe fuse holders?
The US3J models are the 30A frame and the US6J models are the larger frame. Pole count is called out by the last digit: US3J1I is single pole, US6J2I is two pole, US3J3I and US6J3I are three pole. The trailing I on all of them means the holder has the fuse-status indicator built in.
3) Can I land #6 THHN on this fuse holder, and what torque do I use?
The terminals take #2 through #14 AWG, so #6 lands fine. Torque the terminal screws to 35 lb-in. Use a calibrated driver: undertorqued Class J terminations at 600V are a common source of hot joints in a panel.
4) Does this Mersen Class J holder work on a DC solar or battery circuit, not just AC?
It's rated 600V on both AC and DC, so it can be used in DC combiner and battery circuits as well as AC control panels. The description lists renewable energy and solar power systems among the intended applications, alongside motor control centers and process control.
5) What SCCR does this fuse holder carry for my panel's short circuit rating?
200 kA. On a Class J fused branch that lets the holder itself stay out of the way when you calculate the assembly SCCR, since it is not the limiting component in most industrial control panels.
6) Can I use a Littelfuse LSRY plug fuse box cover unit instead of a Mersen UltraSafe Class J fuse holder?
They are not interchangeable. The Littelfuse LSRY series is a plug fuse box cover unit rated 125V 15A, intended for screw-in plug fuses in a residential-style fuse box. The Mersen UltraSafe Class J holder is a DIN rail device rated 600VAC/600VDC at 30A, accepts clip-in Class J fuses, and terminates #2 to 14 AWG conductors at 35 lb-in. Any 600V industrial circuit or Class J overcurrent requirement needs the UltraSafe; the LSRY applies only to low-voltage plug fuse applications.
7) How do I tell if a fuse has blown without pulling it out?
There's an LED indicator on the holder that shows fuse status visually. You read the pole from the panel door rather than opening covers and testing each fuse, which is the main reason to spec the I suffix versions like US3J3I or US6J2I.
8) Is this fuse holder rated for a washdown or outdoor enclosure?
The housing is IP65 rated polyamide, which means dust tight and protected against water jets. That covers washdown areas, marine and offshore installs, and outdoor enclosures. IP65 is not an immersion rating, so it isn't for submerged locations.
9) I need a fuse holder for a wet or washdown location. Does the Mersen UltraSafe work, or should I look at an in-line watertight holder?
The Mersen UltraSafe Class J holder has an IP65-rated sealed polyamide housing that resists dust ingress and water jets, so it is suited to washdown panels, outdoor enclosures, and marine or offshore installations while still mounting on standard DIN rail with LED fuse-status indication. If the protection point is not inside an enclosure at all and has to be spliced directly into a cable run, the Littelfuse WPB1 in-line watertight holder is the different form factor for that condition.
10) Is this RoHS compliant for an export machine build?
Yes, the UltraSafe Class J holder is RoHS compliant, which is listed under its certifications along with the IP65 enclosure rating.
How fast can I get the Mersen US3J1I 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 Mersen US3J1I come with a warranty?
Absolutely. The Mersen US3J1I 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 Mersen US3J1I?
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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