30A Time Delay Melamine Fuse with 600VAC Voltage Rating; RES Series

Time-delay, nonindicating UL Class H fuses have a 10kA interrupting rating (IR) for general purpose use in existing installations where a small-interrupt, slow-blow fuse is needed. They're sometimes used in place of Class K5 fuses to downgrade from a current-limiting system. These renewable fuses have a fusible link that can be replaced after the fuse blows to allow reuse. They tolerate temporary inrush currents without opening, which prevents nuisance-blowing from equipment startups. They open to disconnect an electrical circuit when exposed to sustained loads and short circuits. These fuses have no indicator for identifying a blown fuse, so they're sometimes used with an indicating fuse block or cover.

UL Class H and K5 fuses are used as replacement fuses for overcurrent protection in older HVAC installations. These fuses are dimensionally the same, so they can be interchanged to change from a current-limiting system using Class K fuses to a noncurrent-limiting system using Class H fuses. Class H fuses are used in low-interrupt applications while Class K fuses have a higher interrupting rating.