AJT300 – GOULD 300A 600V CLASS J TIME DELAY FUSE

The AJT300 uses the standard Class J rejection-blade form factor, so it fits any UL-listed Class J fuse holder or fusible disconnect rated for at least 300A and 600V. Common compatible holders include Eaton's JM, Bussmann's JF, and similar Class J-specific blocks. Class H or standard fuse clips will NOT accept a Class J fuse due to the rejection feature.

The Gould/Ferraz Shawmut AJT series has been continued under the Mersen brand (formerly Ferraz Shawmut), so the Mersen AJT300 is a direct replacement. Other industry crosses include the Bussmann LPJ-300SP and the Littelfuse JLLN-300. Northern Breaker Group specializes in hard-to-find and obsolete fuses — contact us for current stock availability.

Time-delay fuses like the AJT300 are specifically designed to ride through the high inrush current that motors, transformers, and other inductive loads draw at start-up — typically 6–10× full-load current for several seconds. A fast-acting fuse of the same ampere rating would nuisance-trip on every start. The AJT300's dual-element design opens quickly on dead short-circuits (up to 200kA interrupting rating) while tolerating legitimate temporary overloads, making it the correct choice for motor branch-circuit protection per Canadian Electrical Code requirements.