<h2>Overview</h2>
<p>The <strong>Bussmann FRN-R-400</strong> is an Eaton Bussmann Series dual-element, time-delay Class RK5 fuse engineered for industrial power distribution and motor control applications. With a 400A current rating and 250VAC/125VDC nominal voltage, this current-limiting cartridge fuse combines the protection characteristics needed for circuits subject to temporary motor overloads and inrush currents while maintaining selective coordination with upstream protective devices.</p>
<h2>Key Features</h2>
<ul>
<li><strong>Dual-Element Design:</strong> Overload element protects against low-level overcurrents; short-circuit element responds to high-fault currents.</li>
<li><strong>Time-Delay Characteristic:</strong> <cite index=”2-2″>Minimum 10 seconds at 500% rated current</cite> prevents nuisance trips on motor inrush.</li>
<li><strong>Current-Limiting:</strong> Reduces let-through current to minimize equipment damage during short circuits.</li>
<li><strong>Selective Coordination:</strong> <cite index=”4-11″>2:1 selective coordination amp ratio prevents overcurrent events from opening upstream Fusetron fuses</cite>.</li>
<li><strong>Rejection Design:</strong> <cite index=”4-6″>Prevents replacement errors with rejection-style design</cite>.</li>
<li><strong>Fiberglass Construction:</strong> <cite index=”4-8>Cylindrical fuse features fiberglass tube construction</cite> with insulated end caps.</li>
</ul>
<h2>Technical Specifications</h2>
<ul>
<li><strong>Catalog Number:</strong> FRN-R-400</li>
<li><strong>Current Rating:</strong> 400A</li>
<li><strong>Voltage Rating:</strong> 250VAC / 125VDC (110–200A range); 250VAC / 250VDC (225–600A range)</li>
<li><strong>Interrupting Rating (AC):</strong> <cite index=”3-1″>200 kA at 250 Vac</cite></li>
<li><strong>Interrupting Rating (DC):</strong> <cite index=”3-1″>20 kA at 250 Vdc</cite></li>
<li><strong>Time-Delay Response:</strong> Minimum 10 seconds at 500% rated current</li>
<li><strong>Body Material:</strong> Fiberglass tube</li>
<li><strong>Terminal Type:</strong> <cite index=”4-7″>Blade terminal connection</cite></li>
<li><strong>Mounting Style:</strong> Holder Mount / Stud Mount</li>
<li><strong>Class:</strong> RK5 (UL current-limiting class)</li>
<li><strong>Body Dimensions:</strong> 2.38″ Diameter × 8.63″ Length</li>
<li><strong>Certifications:</strong> cULus Listed</li>
</ul>
<h2>Typical Applications</h2>
<ul>
<li>Motor control centers and combination starters</li>
<li>Machinery disconnects and safety switches</li>
<li>Industrial power panel boards and branch circuits</li>
<li>Systems requiring motor overload, ground fault, and short-circuit protection</li>
<li>Circuits subject to temporary inrush or surge currents</li>
<li>Industrial automation and process control equipment</li>
</ul>
<h2>Compatibility & Replacements</h2>
<h3>Compatible With</h3>
<ul>
<li>Class RK5 and Class K5 fuse blocks and holders</li>
<li>RM 250-volt fuse blocks (RM25400 series for 225–400A ratings)</li>
<li>Class R fuse reducers (for downsizing applications)</li>
<li>Eaton/Bussmann series fuse holders designed for RK5 cartridge fuses</li>
</ul>
<h3>Replaces / Drop-In Replacement For</h3>
<ul>
<li>Older Class K5 dual-element fuses in compatible fuse blocks</li>
<li>Renewable or one-time non-time-delay fuses rated 400A (when switching to dual-element protection)</li>
</ul>
<h3>Works With</h3>
<ul>
<li>Motor control circuits and overload protection systems</li>
<li>Industrial power distribution networks requiring selective coordination</li>
<li>Short-circuit protection schemes in accordance with NEC and UL 1077 standards</li>
<li>Eaton/Bussmann Branch Circuit Protection product line</li>
</ul>
