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Ed Anderson wrote:
Yes, Bill, that is what I understand as well. BUT, if you are fused for the equipment load, the wiring is automatically protected (in a proper design). In fact, by using a smaller rated fuse (designed just to protect the equipment rather than the wiring) you are even better ensuring that the wiring won't carry a dangerous load and catch fire. So again, I can see no rational reason for fusing to protect the wire rather than a lower rated fuse/CB to protect the equipment (regardless of whether it actually protects the equipment). But, then I've never been accused of being the brightest turnip on the tomato truck.
Ed
The equipment needs at least X current. The wire can only have Y current. The fuse's rated value can lie anywhere between X and Y.
By moving the value closer to X, you add more protection to the equipment...but subject yourself to nuisance trips. Better to go with a circuit breaker.
Push the value toward Y, and you move out of the nuisance trip zone. A fuse would do just a well then, because if it ever tripped because of bad equipment, that piece is already toasted...and good.
I expect that airliners and the military like circuit breakers because of institutional momentum, and the fact that they actually have multiple people on the airplane to do something about a popped breaker besides just pushing it back in.
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