Mersen OT125 - Fuse OT - Class K5 - Fast-Acting 250VAC 250VDC 125A Blade Amp-Trap®
Mersen

OT125

Alternate Item Number: OT125

UPC: 782001700300


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Overview

The Mersen OT125 (SKU: OT125) is a Class K-5 fast-acting fuse engineered for reliable overcurrent protection in feeder and branch circuits. Rated for 250VAC/DC and 125A, it delivers a 50,000A AC interrupting rating (20,000A DC), ensuring robust fault protection for non-motor loads. Ideal for lighting, heating, and resistive applications, this fuse minimizes downtime and equipment damage during fault conditions with its fast-acting response. The OT125 is UL Listed to Standard 248-9 and CSA Certified to C22.2 No. 248.9, meeting stringent safety and compliance requirements. Its low-cost design provides high-value protection while being compatible with standard Class K-5 fuse blocks. For Canadian applications requiring low melting-point designs in 15-60A ratings, the OTN series is recommended. Distributed by Gross Automation for fast delivery and expert support.
  • Class K-5 fast-acting fuse for non-motor loads (lighting, heating, resistive circuits)
  • Rated 250VAC/DC, 125A, with 50kA AC / 20kA DC interrupting rating
  • UL Listed to Standard 248-9 and CSA Certified to C22.2 No. 248.9
  • Low-cost protection solution compatible with standard Class K-5 fuse blocks
  • Fast response minimizes downtime and equipment damage during faults

Specifications

AC Voltage Rating
250 V
Amperage Rating
125 A
Application
Feeders Branch circuits Resistive heating Residential and small commercial installations
Body Material
PolyTube
Brand Name
Mersen
Class
Class K5
Connection
Blade
Connection Material
Tin-Plated Copper
Connection Type
Blade
Current Rating
125 A
DC Voltage Rating
250 V
Interrupt Rating
50 kA
Mounting
Clip
Series
Amp-Trap®
Size
7.13 x 1.56 in
Size
181.102 x 39.624 mm
Special Features
Easy to read imprint label for quick recognition and replacement Low cost for high protection value
Standard
UL Listed to Standard 248-9 File E2137 CSA Certified to Standard C22.2 No. 248.9 (The Canadian Electrical Code requires these fuses in ratings 15 through 60A to be of the low melting point design use OTN 15-60.) Self-certified for DC per UL248
Sub Brand
Amp-Trap®
Type
Class K5
Voltage Rating
250 VAC
Package Dimensions (L x W x H)
7.13 in x 1.56 in x 1.56 in
Package Dimensions (L x W x H)
181.102 mm x 39.624 mm x 39.624 mm
Package Weight (Imperial)
0.733 lb
Package Weight (Metric)
0.332 kg
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POWR-JAW clamps improve the contact between fuse and clip. The unnecessary heat from poor contact due to the loss of spring force in the clips can cause nuisance fuse opening and premature aging of surrounding components. High temperature phenolic resin knob designed for the most severe environments 7 sizes to provide effective coverage. Simple design makes installation easy.

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POWR-JAW clamps improve the contact between fuse and clip. The unnecessary heat from poor contact due to the loss of spring force in the clips can cause nuisance fuse opening and premature aging of surrounding components. High temperature phenolic resin knob designed for the most severe environments 7 sizes to provide effective coverage. Simple design makes installation easy.
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Frequently Asked Questions about Mersen

What industries and applications are Mersen products used for?

Mersen products are used across diverse industrial sectors including solar power, electric vehicles, buildings/construction, industrial automation, power distribution, HVAC, elevators, telecommunications, and specialty manufacturing. Key application areas include circuit protection, surge protection, battery module protection, electrical safety systems, and power management for residential, commercial, and utility-scale installations.

What are the main product lines offered by Mersen?

Mersen offers five primary electrical power product lines: IEC and UL/CSA Fuses and Fusegear, Surge Protection, Low Voltage Disconnect Switches, Power Distribution Blocks, and Engineered Solutions. Their comprehensive range includes specialized components like high-speed fuses, modular fuse holders, surge arresters, and custom-engineered electrical protection systems for industrial and power management applications.

What are the key features of Mersen products?

Mersen products feature advanced electrical protection and power management solutions with key characteristics including finger-safe design, compact modularity, and high-performance safety features. Their product lines span electrical power components like fuses, surge protection, power distribution blocks, and specialized solutions for industrial, solar, and building applications. Critical features include UL/CSA approvals, high short-circuit current ratings, and innovative technologies like the Fuse Control™ program that minimize electrical risks and optimize system performance.

What environmental ratings do Mersen products have?

Mersen products meet rigorous environmental ratings across multiple standards, including UL 508A Type 1, 2, 3, 4, 4X, 12, and 13, CSA Type 1, 2, 3, 4, 4X, 12, and 13, and NEMA Type 1, 2, 3, 4, 4X, 12, and 13. They feature IEC 60529 IP66 protection, with enhanced UV inhibitors for outdoor weathering and operating temperatures ranging from -40°C to 130°C (-40°F to 266°F). These ratings ensure superior protection in wet, corrosive, and challenging industrial environments.

What accessories are available for Mersen products?

Mersen offers multiple accessories for their fuse blocks and systems, including safety pullers (DFC3M and DFC3LP), DIN-rail adapters (DRM), bus bars, auxiliary contacts, and specialized mounting hardware. Key accessories include the DFC3M safety puller for 1-1/2" x 13/32" midget or Class CC fuses, the DRM adapter for mounting 303 series fuse blocks on DIN-rail, and UltraSafe fuse module accessories like bus bars and auxiliary contacts that enable module interconnection and monitoring.

How are Mersen products typically installed?

Mersen products are typically installed in electrical distribution systems, control panels, and industrial automation environments using multiple mounting options. These include service entrance panel mounting, distribution panel installation, control panel DIN rail mounting, and custom engineered solutions like Fused Coordination Panelboards. Installation depends on the specific product type, such as fuses, surge protective devices, or switches, and is designed to provide electrical protection and circuit safety in various industrial and commercial applications.

What certifications and standards do Mersen products comply with?

Mersen products are certified to multiple international standards, including UL (Underwriters Laboratories), CSA (Canadian Standards Association), CCC (China Compulsory Certification), and EAC (Eurasian Conformity). Our products meet rigorous safety and performance standards for industrial applications across North America, China, Russia, and other global markets, ensuring compliance and reliability in electrical power and advanced materials solutions.

What technical support does Mersen offer?

Mersen provides comprehensive technical support through multiple channels, including technical experts located in your time zone who can assist with product selection, application guidance, and troubleshooting. Their Fuse Control™ program offers a free Fuse Inventory Audit & Analysis, and customers can access technical resources through their sales representatives and online platform ep.mersen.com.