026303.5WRT1L

FAQFrequently Asked Questions

• Can I use 026303.5WRT1L in a 250 VAC mains input stage that has inrush current from a capacitive power supply? 026303.5WRT1L is a fast-blow Littelfuse PICO II 263 fuse with a 3.5 A, 250 VAC rating, so it can be used in a mains input path only if the expected steady-state current and inrush profile stay within its time-current behavior. In circuits with large input capacitors, motor starts, or transformer magnetizing surge, a fast-blow part like 026303.5WRT1L may nuisance-open unless the surge profile is already controlled by NTC, soft-start, or other inrush limiting.
• Is 026303.5WRT1L suitable for replacing a slower fuse in the same 3.5 A circuit? 026303.5WRT1L is not a like-for-like substitute for a time-delay fuse. Because it is a fast-blow device, it responds more quickly to overload and surge events. If the original design relied on a slow-blow characteristic to survive startup current, replacing it with 026303.5WRT1L can change startup behavior and cause unwanted opening even when the average load current is normal.
• What should I check before using 026303.5WRT1L as a drop-in replacement for another 3.5 A axial fuse? For 026303.5WRT1L, the main checks are fuse speed, interrupting behavior, physical size, lead form, and regulatory approvals. A replacement should match the circuit’s surge profile, fit the board hole spacing and body clearance, and meet the same mains safety requirements. The substitute parts listed for 026303.5WRT1L, including 026303.5WRT1 and 026303.5HAT1L, should still be verified against the full mechanical and electrical requirement set before release.
• Can 026303.5WRT1L be used in both AC and DC applications? 026303.5WRT1L is rated for 250 V AC and is described as an AC/DC board-mount fuse, so it may be used in DC circuits only when the applied DC voltage, fault current, and opening conditions stay within the device limits. DC interruption is often more demanding than AC interruption, so the circuit’s available fault energy and the specific DC working voltage should be reviewed instead of assuming AC and DC behavior are equivalent.
• How do I know if 026303.5WRT1L has enough interrupting capacity for my design? 026303.5WRT1L has a breaking capacity of 50 A at rated voltage, so the available fault current in the end application should be below that level under the worst credible condition. If the supply can source more than 50 A into a short, the fuse may not clear the fault in the intended way, so the upstream impedance, transformer or supply fault current, and any battery or bulk-capacitor contribution should be evaluated.
• Is 026303.5WRT1L appropriate for high-surge industrial equipment or motor loads? 026303.5WRT1L can work in industrial equipment only when the operating current is stable and the start-up surge is modest. For motors, solenoids, large transformers, or high-capacitance front ends, the fast-blow characteristic and 2.33 I²t value may not tolerate repetitive surge events. In those cases, engineers often compare the actual inrush waveform against the fuse’s time-current curve and may choose a different fuse family if nuisance opening appears in testing.
• Can I use 026303.5WRT1L on a PCB where space is tight? 026303.5WRT1L is an axial through-hole fuse with a body size of about 3.94 mm by 7.11 mm, so it is practical when the board has room for an axial footprint and adequate creepage and clearance. It is less convenient where SMT-only assembly, very low profile placement, or automated cartridge-style fuse handling is required.
• What is the practical difference between 026303.5WRT1L and 026303.5WRT1? 026303.5WRT1L and 026303.5WRT1 are closely related substitute options in the same Littelfuse 263 family, but the final suitability depends on exact construction, packaging, and any minor manufacturing or qualification differences tied to the suffix. For design-in or second-sourcing, the engineer should confirm the electrical rating, mechanical dimensions, and approval markings for 026303.5WRT1L against the target BOM and compliance documents before treating the two as interchangeable.
• Is 026303.5WRT1L a good choice for equipment that must meet CSA, PSE, or UL requirements? 026303.5WRT1L carries CSA, PSE, and UR approval agency listings, which can simplify compliance work when the end product is being evaluated in those markets. The fuse itself still needs to be applied within its rated voltage, current, temperature, and interrupt conditions, and the final system approval depends on the full product design rather than the fuse alone.
• How does temperature affect the behavior of 026303.5WRT1L in long-term industrial use? 026303.5WRT1L is specified for -55°C to 125°C ambient operation, but fuse opening behavior still shifts with temperature because element heating adds to ambient heating. In high-temperature enclosures, the same operating current can produce a higher effective stress on the fuse, reducing margin against nuisance opening. Designs with elevated ambient temperatures usually benefit from current derating and thermal testing at the actual enclosure temperature.
• Can 026303.5WRT1L be used as a safety fuse on the primary side of a small offline power supply? 026303.5WRT1L can be used on a primary side only if the supply’s normal inrush, steady current, and fault energy match its fast-blow characteristics and 50 A interrupting capability. Small offline supplies often have capacitor charging peaks and rectifier stress that may not pair well with a fast fuse unless the power stage has been validated with the actual fuse in place.
• What should I consider if I am replacing a fuse with 026303.5WRT1L in an existing design? When replacing an existing fuse with 026303.5WRT1L, the first checks are current rating, fast-blow behavior, voltage rating, and physical fit. After that, review the PCB hole pattern, lead spacing, thermal rise around the fuse, and the fault current available from the source. Even if the nominal rating matches, 026303.5WRT1L can behave differently from a slow-blow or higher-I²t part during startup or transient events.