Eaton Bussmann 3-Pole Industrial Fuse Block, AC: 600 VAC, DC: Not Rated, 110 to 200A, Series NOS

These fuse blocks are compatible with UL Class H and K fuses that commonly provide overcurrent protection in older HVAC installations. They're used with Class H fuses for a noncurrent-limiting system with small interrupting ratings or Class K fuses for a current-limiting system with high interrupting ratings. Fuse blocks with spring-reinforced clips hold fuses tightly in place to maintain full electrical contact.

UL Class and midget fuse blocks accept fuses sized and rated according to UL Class or midget specifications. They have an open top for access to fuses, clips or studs for securing fuses within the block, and terminals for connecting to the circuit. These fuse blocks are either bolted down or mounted on a DIN rail to hold them in place. They're commonly paired with fuse box covers to enclose the fuses and prevent accidental contact. They are nonindicating, so there's no visual signal when a fuse is blown.