Mersen UltraSafe Class J Fuse ...
IN STOCK (leaves warehouse same day if ordered before 3pm ET)
$115.24
Mersen UltraSafe Class J Fuse Holder, 600VAC/600VDC

Mersen UltraSafe Class J Fuse Holder, 600VAC/600VDC

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Model: US3J1

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

$115.24
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Mersen US3J3 UltraSafe Class J Fuse Holder, 600VAC/600VDC 30A 3-Pole

The Mersen US3J3 UltraSafe Class J Fuse Holder delivers dependable circuit protection for demanding industrial and commercial electrical systems. This 3-Pole, DIN Rail mount holder supports dual 600VAC/600VDC operation at 30A, with a 200 kA short circuit current rating (SCCR) for critical fault protection. Durable polyamide construction and IP65 environmental protection make it suitable for challenging panel environments, while clip-in fuse installation simplifies maintenance and service access.

Key Features

  • Dual Voltage Rating: 600VAC/600VDC compatibility supports both AC and DC circuit protection in a single device.
  • Ampere Rating: 30A max fuse rating for reliable overcurrent protection.
  • 3-Pole Configuration: Consolidates three-phase or multi-circuit fuse protection into one compact assembly.
  • High Short Circuit Rating: 200 kA SCCR delivers exceptional fault current interruption capability for critical system protection.
  • IP65 Environmental Protection: Sealed enclosure guards against dust and water ingress in demanding industrial environments.
  • DIN Rail Mounting: Standard rail compatibility enables quick installation and space-efficient panel integration.
  • Durable Construction: Polyamide body insulating material provides excellent electrical isolation and mechanical strength.
  • Clip-in Fuse Installation: Tool-free fuse replacement reduces maintenance time and improves service accessibility. Accommodates #2 to 14 AWG conductors with a 35 lb-in torque rating for secure wiring connections.

Certifications & Compliance

  • RoHS Compliant
  • IP65 Rated Enclosure

Technical Specifications

  • Rohs Compliant: Yes

Typical Applications

  • Industrial Control Panels and Motor Control Centers
  • Commercial Electrical Distribution Systems
  • Manufacturing Equipment Protection
  • Process Control and Automation Systems
  • Power Distribution in Critical Facilities
  • Data Center and Telecommunications Infrastructure

Why Mersen?

Mersen UltraSafe fuse holders combine proven circuit protection engineering with practical safety features for professional electrical work. RoHS compliant construction, a durable polyamide body, and IP65 environmental sealing support long-term performance in demanding industrial settings, while the 200 kA SCCR and dual 600VAC/600VDC rating give installers confidence in critical power distribution and control panel applications.

Manufacturer Resources

Mersen Product Catalog

Product Specs

Product Group:
Circuit Protection
Ampere Rating:
30 A
Torque Rating:
35 lb-in
Installation Mounting:
DIN Rail
Fuse Class:
Class J
Fuse Installation Method:
Clip-in
Max Fuse Rating:
30 A
Department:
Electrical
Product Type:
Fuse Holder
Product Subgroup:
Fuse Holders & Blocks
Product Height:
3.15 in
Product Length:
4.49 in

Mersen US3J1 – Frequently Asked Questions

1) Will the Mersen UltraSafe US3J fuse holder accept any Class J fuse up to 30 amps?
The UltraSafe US3J holder is built for Class J fuses only, with a 30 A maximum fuse rating. Class J fuses have their own dimensions and rejection features, so a Class CC, Class T, or midget fuse will not clip into it. Fuses install clip-in, no tools needed.
2) Can this Mersen fuse holder be used on a 600V DC circuit, not just AC?
Yes, the UltraSafe US3J is rated 600VAC and 600VDC, so it covers DC bus and drive circuits as well as AC distribution. It also carries a 200 kA short circuit current rating, which is what lets it sit in a panel with a high available fault current.
3) Can a Littelfuse WPB1 in-line fuse holder be used instead of the Mersen US3J Class J holder in a control panel?
No, they solve different problems. The Mersen US3J UltraSafe is a Class J, 30 A, DIN rail mounted holder with clip-in fuse installation, built for panel interiors where fuses sit on a rail alongside other devices. The Littelfuse WPB1 is an in-line watertight fuse holder, which is a cable-mounted device spliced into a run rather than rail mounted, and it is not a Class J holder. If the drawing calls for Class J fusing on a DIN rail, the WPB1 is not a substitute.
4) How does the US3J mount in a control panel, and does it need a subpanel bracket?
It snaps onto standard DIN rail, so no separate mounting plate or bracket is needed beyond the rail already in the enclosure. That also makes it straightforward to gang holders side by side for multiple circuits.
5) What wire size and terminal torque should I use when landing conductors on the US3J holder?
The terminals take #2 through 14 AWG conductors and are torqued to 35 lb-in. Use a torque screwdriver or wrench on that value, since under-torqued terminals are the usual cause of hot spots on fused disconnect blocks.
6) Is this fuse holder suitable for a washdown or dusty plant environment?
The UltraSafe holder is IP65 rated, so it is sealed against dust and low pressure water jets, and the body is polyamide for insulation and mechanical strength. It is still a panel-mount DIN rail device, so it belongs inside an enclosure rated for the environment rather than mounted in the open.
7) I need a fused disconnect for a 125V lighting branch with plug fuses. Will this Mersen work?
No. The UltraSafe US3J takes Class J cartridge fuses at 600V and clips into DIN rail. For an Edison-base plug fuse at 125V, 15 A, look at the Littelfuse LSRY Series plug fuse box cover unit instead.
8) What is a simpler fuse holder option for a 120 V lighting or receptacle circuit where the Mersen US3J is more than the job needs?
The Mersen US3J UltraSafe is a 600VAC/600VDC Class J holder rated 30 A with a 200 kA SCCR, sized for industrial control panels and motor control centers. For a low-voltage branch circuit protected by a plug fuse, the Littelfuse LSRY Series plug fuse box cover unit is rated 125 V 15 A and takes a screw-in plug fuse rather than a Class J cartridge. Confirm the fuse class your circuit is specified for before swapping, since the two accept entirely different fuse bodies.
9) For a wet or washdown location, is the Mersen US3J or the Littelfuse WPB1 the right fuse holder?
Both address moisture, but in different ways. The Mersen US3J UltraSafe carries an IP65 sealed body and mounts on DIN rail, so it protects the fuse inside a panel that may see dust and water ingress. The Littelfuse WPB1 is a watertight in-line holder intended to be run in the wiring itself rather than mounted in an enclosure. If the fuse sits in a panel, the US3J applies; if it sits out on a cable run outside an enclosure, the in-line WPB1 is the form factor that fits.
10) I only need to protect a single conductor. Do I have to buy the 3-pole Mersen holder?
No. The Mersen US3J UltraSafe is built in 1-pole (US3J1), 2-pole (US3J2) and 3-pole (US3J3) configurations, all Class J and all DIN rail mount, so a single-conductor circuit can use the US3J1 rather than a three-phase block. If the circuit is a low-voltage 125 V branch on a plug fuse instead of a Class J cartridge, the Littelfuse LSRY plug fuse box cover unit at 125 V 15 A is the different route to take.
11) Does the Mersen UltraSafe fuse holder come with fuses?
The US3J is the holder only. You order the Class J fuses separately, sized at or below the 30 A maximum for the holder and coordinated with the load you are protecting.
How fast can I get the Mersen US3J1 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 US3J1 come with a warranty?
Absolutely. The Mersen US3J1 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 US3J1?
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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