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Blue Sea Systems 5121 Class T Fuse 400 Amp JJN Fast-Acting

Manufacturer

Blue Sea Systems

<p>When electrical reliability can mean the difference between a successful voyage and a dangerous situation, marine professionals and enthusiasts turn to Blue Sea Systems. Founded in 1992, this American manufacturer has built a reputation for creating electrical components specifically engineered to withstand the unforgiving marine environment. Every product reflects a commitment to safety standards and real-world performance that has made Blue Sea Systems a leading name in marine and specialty vehicle electrical systems.</p> <h3>Engineering for the Marine Environment</h3> <p>Blue Sea Systems develops and manufactures dependable AC and DC electrical products for marine and specialized vehicle applications, designed in the USA and engineered to excel in challenging environments. The marine environment presents unique challenges—salt spray, constant vibration, temperature extremes, and moisture exposure—that can quickly degrade inferior electrical components. Blue Sea Systems addresses these challenges through careful material selection, rigorous testing protocols, and designs that prioritize both safety and serviceability. Their components are engineered for marine use and align with the intent of ABYC E-11: AC and DC Electrical Systems on Boats and relevant USCG electrical regulations.</p> <h3>Commitment to Safety Standards</h3> <p>Safety standards aren't just guidelines for Blue Sea Systems—they're fundamental to every product design. All Blue Sea Systems marine battery disconnect switches comply with the ABYC C-7 certification, demonstrating their commitment to meeting and exceeding industry safety requirements. The company maintains ABYC-certified employees across multiple departments, from engineering to technical support, ensuring deep expertise in marine electrical system design and installation standards.</p> <h3>Comprehensive Product Range</h3> <p>Blue Sea Systems offers an extensive catalog designed to address every aspect of marine electrical systems. Their <a href="/7262-blue-sea-systems-circuit-breakers-200260">circuit breakers</a> provide resettable overcurrent protection with trip-free designs and clear trip indication for quick diagnostics. For power management, their <a href="/7262-blue-sea-systems-battery-switches-manual-200149">battery switches</a> offer reliable methods for controlling battery banks and disconnecting loads during storage or emergencies, with ABYC C-7 compliance guaranteed.</p> <p>Monitoring system health is critical aboard any vessel, which is why their <a href="/7262-blue-sea-systems-battery-monitors-volt-meters-200146">battery monitors and volt meters</a> provide accurate real-time data to help operators make informed decisions about power usage and charging. The company's <a href="/7262-blue-sea-systems-terminal-blocks-bus-bars-201059">terminal blocks and bus bars</a> create organized, serviceable connection points that simplify installation and future modifications. For keeping batteries properly charged, Blue Sea Systems offers <a href="/7262-blue-sea-systems-battery-chargers-200141">battery chargers</a> engineered with features like automatic charging relay compatibility and proper charge profile management.</p> <h3>Built by Boaters, for Boaters</h3> <p>Blue Sea Systems was founded based on a commitment to create innovative high quality marine electrical products to improve the safety, simplicity, and reliability of boating, with employees who are active boaters applying their passion to designing, developing, and building products. This firsthand experience translates into practical features like modular layouts, standardized footprints, and installer-centric designs that streamline panel work and serviceability. The result is a product line that addresses real challenges faced on the water, backed by comprehensive technical documentation and support resources that help both professionals and DIY enthusiasts complete installations with confidence.</p>

Part Number

5121
06/01/2036 5:03 AM
Sale Price

$70.74

In Stock (10+)

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Usually delivered within 2 days

free shipping

FREE SHIPPING

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No Hassle Returns

No Hassle Returns

Live-in-stock inventory

Live-in-stock inventory

Fitment guaranteed

Fitment guaranteed

Product Details

The Blue Sea Systems 5121 is a 400 amp Class T fast-acting fuse designed for high-amperage DC electrical systems in marine, RV, and other mobile applications. This JJN-style fuse provides critical overcurrent protection with an extremely fast response time to prevent electrical system damage.

Key Features:

  • 400 amp rating for high-current DC circuits
  • Class T fast-acting design with extremely fast short-circuit response
  • 20,000 Ampere Interrupt Capacity (AIC) for superior protection
  • UL Listed to standard 248-15 for quality assurance
  • DC tested to UL standard 198L for reliable performance in DC systems
  • JJN configuration compatible with Class T fuse blocks and holders

Blue Sea Systems Class T fuses are engineered for demanding marine and mobile power applications where reliable overcurrent protection is essential. The fast-acting design quickly interrupts fault currents to protect expensive inverters, battery banks, and other critical electrical components.

Products specifications

Amps

400A

Fuse Type

JJN

Size

2.75''L x 1.31''W

great transaction, very fast shipping

So far so good

Excellent shipping received very fast and well packaged

This was my first experience ordering from Autoplicity. The ordering process was easy, I got the parts that I wanted at the best price I could find, and they came quickly. I can't ask for more than that.

Great experience with autoplicity. Fast shipping. Ordered on 5/31 got bed cover on 6/2. Fit truck perfect.

Good pricing. Order processing is fast and easy.

Easy and fast

great price on product and shipping and shipping was very fast

Good so far

Good

clear product description. Quick checkout process.

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