Figuring Proper Fuse Size

mena661 wrote:

CA Traveler wrote:
Fuses protect the equipment and the wiring. Wiring can develop a short and you certainly want a fuse to protect it and the equipment.

Fusing is for protecting wire. Regardless, this does not make any sense (at least not to me) if you have properly sized wire. In a 300W inverter, the max it draws is 30 amps from the batteries (maybe it can draw up to its surge rating IDK). If I have wiring that can accommodate 100-380 amps (this is my setup), how is a short going to do anything to the wire? If the equipment shorts internally, it has fuses and protection circuits to handle that. Not to mention, shorts ALWAYS lead to an open and usually in a short period (pun) of time because internal circuitry is not designed to run over its design parameters. I'd be more worried about the equipment catching fire than wiring melting.

What you're missing is that shorts are abnormal and don't obey any rules or preconceived notions. Inverters may/may not have any fuses to protect the heavy DC draw electronics and they don't need to because the fuse should be near the battery. But if it does have a fuse what if the short occurs between it's fuse and the terminal lug? You don't want the wiring to overheat and cause a fire or cause the battery to overheat and be destroyed or cause a fire.