Quick answer: UL 248-13 covers low-voltage fuses (up to 600V AC/DC) for general and semiconductor protection, while UL 248-14 specifically covers fuses for semiconductor device protection (high-speed aR/gR class, up to 1000V AC/DC). For EV and ESS high-voltage DC systems above 600V, refer to UL 248-13 supplemented by manufacturer DC ratings.

What Are UL 248 Standards?

UL 248 is the Underwriters Laboratories series of safety standards for low-voltage fuses. The series is divided into numbered parts, each covering a specific fuse type or application. The two most commonly referenced parts for industrial and DC applications are UL 248-13 and UL 248-14.

Understanding which standard applies to your fuse is essential for compliance, safety and proper circuit protection design — especially in high-voltage DC systems like electric vehicles (EV), battery energy storage systems (ESS) and solar photovoltaic (PV) installations.

UL 248-13: Low-Voltage Fuses

UL 248-13 — titled “Low-Voltage Fuses” — covers fuses rated up to 600V AC and 600V DC. This standard includes a wide range of fuse classes:

• Class H, K, RK1, RK5 — general-purpose and time-delay fuses for branch circuit protection
• Class T — fast-acting fuses for high inrush current applications
• Class J — current-limiting fuses with high breaking capacity
• Class L — high-amperage fuses (601A-6000A)
• Class CC — compact current-limiting fuses

UL 248-13 fuses are widely used in industrial control panels, motor circuits and general power distribution. For more specialized DC applications, manufacturers may provide supplementary DC ratings beyond the standard 600V, as seen in products from DC Fuse Link and GFEFuse.

UL 248-14: Fuses for Semiconductor Devices

UL 248-14 — titled “Fuses for the Protection of Semiconductor Devices” — covers high-speed fuses specifically designed to protect sensitive semiconductor components such as diodes, thyristors, IGBTs and MOSFETs.

These fuses operate in the aR (partial-range semiconductor protection) and gR (full-range semiconductor protection) classes. Key characteristics include:

• Ultra-fast opening speed (typically < 1ms at high fault currents)
• High breaking capacity (up to 200kA)
• Rated up to 1000V AC/DC
• Low I²t (let-through energy) to protect semiconductors

UL 248-14 fuses are essential in variable frequency drives (VFD), UPS systems, welding equipment, rectifiers and EV inverter protection.

Side-by-Side Comparison

Which Standard for High-Voltage DC (EV/ESS/Solar)?

For high-voltage DC systems operating above 600V — such as EV battery packs (400V-1000V), utility-scale ESS (up to 1500V) and solar PV strings (1000V-1500V) — the selection requires careful consideration:

1. Below 600V DC: UL 248-13 certified fuses with DC ratings are appropriate.
2. 600V-1000V DC: Look for UL 248-14 high-speed fuses or UL 248-13 fuses with manufacturer-extended DC ratings.
3. Above 1000V DC: No UL standard directly covers these voltages. Fuses must be evaluated to UL 248-13/14 with supplementary DC ratings, or certified to IEC 60269-6 (fuses for DC applications).

For EV and ESS applications, EssFuse high-voltage DC fuses are tested and certified to UL 248-13 with DC ratings up to 1500V, providing reliable protection for next-generation battery systems.

Need Help Selecting the Right Fuse?

Our engineering team can help you determine the correct UL standard, fuse class and rating for your specific application. Contact EssFuse for a free consultation, or explore our application guides for EV, ESS, solar and industrial systems.

For additional technical resources, visit our partners at EssFuse.com for comprehensive fuse selection tools and datasheets.