240alt fuse

[06RTCharger]

So i have a 240amp mechman alt waiting to be put in. I used to think just fuse for wire size and ur good. But ive learned a lil from some of the OGs here and a smarter way to go is to use a fuse thats rated right at or below ur max current being pushed/drawn on that specific wire run. So if my alt will push 240amps maximum, then my alt to battery positive wire should be fused close as possible to 240 or even slightly below when using an ANL fuse. ANL fuses dont blow quick and will handle going slightly over its rating for short periods and still be fine. Am i correct with these thoughts so far? 

Then the reason for fusing my 4/0 (700amp@20ft capable) run from alt to battery at 240-225A instead of 600A would be to safely know when and if the alt is being weird and putting out more power than it should, meaning somethings wrong. Had i used a 600A fuse on my 4/0, my fuse wouldnt let me know anything is going wrong with the alt unless it pushed out more than 600 amps. Still good on my thoughts?

Ok so if all that is right, the real question is does this alt max out at 240 when its in good/normal working condition? Or do alternators normally spike up higher than its rating? If so, what is the normal peak of this ALT? As always, thanks guys. 

[ShadeTreeMechanic]

The rating of 240a would be the max constant output @ rated voltage with no headroom left. It will probably be somewhat less at idle when hot. The output of the alternator is determined by the load. It won't all of the sudden put out more amperage unless the load from the system increases or a short occurs. The regulator can fail and cause the voltage to be high, otherwise a malfunction will cause less output.

[06RTCharger]

17 hours ago, ShadeTreeMechanic said:

The rating of 240a would be the max constant output @ rated voltage with no headroom left. It will probably be somewhat less at idle when hot. The output of the alternator is determined by the load. It won't all of the sudden put out more amperage unless the load from the system increases or a short occurs. The regulator can fail and cause the voltage to be high, otherwise a malfunction will cause less output.

Ok cool, so a fuse at or even slightly below 240 would work perfect for alt-to-batt run? 

[ShadeTreeMechanic]

Well it would be 240a at rated voltage. If the voltage were lower like 12v then it could possibly be more. Most people don't fuse the alternator because it is such a short run. The only thing that a fuse will do is protect the cable in the event of a short. Like a car accident but because it is such a short run that the battery being smashed is a bigger concern. At this point having good battery terminal covers is a must.

[06RTCharger]

16 minutes ago, ShadeTreeMechanic said:

Well it would be 240a at rated voltage. If the voltage were lower like 12v then it could possibly be more. Most people don't fuse the alternator because it is such a short run. The only thing that a fuse will do is protect the cable in the event of a short. Like a car accident but because it is such a short run that the battery being smashed is a bigger concern. At this point having good battery terminal covers is a must.

My cars one of those with the stock battery in the trunk :/ so my alt to batt run is the longest run in the vehicle. Im going to fuse at the alt and also at the battery because its so long. Just want to be sure the fuse is at a good rating for the alternator. My wire run is 4/0Knu, i almost went with 600amp marine fuses becuase "fuse for wire" was my guide.