A4BY800 – GOULD 800A 600V CLASS L FAST ACTING FUSE

Class L fast-acting fuses like the GOUA4BY800 are designed primarily for the protection of feeders, mains, and equipment such as transformers, bus ducts, and service entrances where a fast response to short-circuit faults is required. Because they respond very quickly to overcurrents, they are generally NOT recommended as the sole protection for motor branch circuits — a time-delay (dual-element) Class L or Class RK5 fuse is preferred for motor loads. If you're unsure which fuse class suits your application, our team is happy to advise.

Yes — Class L fuses are standardized by ANSI/UL 248-10, so the GOUA4BY800 (Gould/Mersen A4BY800) is dimensionally and electrically interchangeable with equivalent 800A 600V Class L fast-acting fuses from other manufacturers, including the Bussmann KRP-C-800SP and Littelfuse L70S800. Always verify the replacement matches the original in ampere rating, voltage rating, class, and speed (fast-acting vs. time-delay) before installing.

Absolutely. Sourcing obsolete and hard-to-find fuses and breakers is our specialty at Northern Breaker Group. We maintain extensive inventory and supplier networks across Canada and internationally. If the GOUA4BY800 is no longer in regular distribution, we can locate new-old-stock, a verified cross-reference, or an approved equivalent. Contact our Calgary, Edmonton, or Vancouver counter for a quote and availability check.