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power center fusable link rating

Anthropy

NAXJA Forum User
Location
Iowa
Anyone know what the amperage rating is for the fusable link on the power center next to the battery.

I think it is 100 amps, but not sure.


Tom Dennis
 
What year is your rig? I haven't seen a fusible link for a 100 amp load. If you blew yours, you can install a fuse holder and 20 amp fuse to start with to check things out. Then go from there.
 
Mine is a '96. on my power distribution center next to the battery, there are two posts. One post is where the positive battery lead attaches and the other side looks as if it is powering the load center. In between the two posts is a 12 gauge wire labled as fuseable link.

Was I incorrect in thinking this is the power for the load center and if so, what does it power?

BTW - I did not fry mine, I am just interested in upgrading my wireing.


Tom Dennis :patriot:
 
I did this upgrade over a year or so ago (you may be able to find posts from then), and I could never satisfy my self as to the rating. In the end I got a 100amp fuse based on the logic that that was what my alternator was rated for and thus I wanted to be able to use all 100amp, but that if the system was “asking” for any more I wanted the fuse to go. The stock link was likely rated based on what the stock alt was rated for or lower based on the highest draw state for the stock equipment. So if you want to have access to the full capability of your equipment for lighting/winches etc. then the rating of the original link is really the wrong question. The fusible link is there to protect against a dead short anywhere in the system and if you have one the 100amp fuse will let go.
Just as a note, there are now breakers available that can handle 100amp that would be nice, but if you use a fuse you need one that has a slow response, because other wise your fan motor turning off at the same time as the lights are on etc. may trip the fuse. Another thing; I left the old wire/fusible link from the alt to the power point hanging from the loom just in case I need to go back to the old system to get me home. I hope that was helpful. I love my new system everything works better; it even fixed my voodoo intermittent a/c problem.
 
Any sources for the circuit breakers?

Also, I agree with the slow blow fuse. Many electrical devices have an in-rush amperage that is much higher than the acutal name plate rating of the device.

Typically, a mulitplier of 1.5 is used for fuse rating. So if the device is rated at 10 amps then one needs to mulitply by 1.5 to get 15 amps rating for the fuse.
 
Here are two places to get the breaker. I think I will use one to run power to the back of my truck for OBA and whatever.
http://www.4by4connection.com/manrescirbre.html
http://www.extremeoutback.com/index.cgi?cart_id=175133.21115&pid=41
I got my maxi fuse from west marine as described by some article flouting around.
The failure that the stock fusible link is there to protect is a diode failure in the voltage regulator (part of the alternator). That would cause a low resistance/high current situation In any other dead short failure in that system the voltage regulator would limit the voltage to 14 and therefore the current to near 0). I think the 1 to 1.5 rule is more appropriate for much lower current situations. I think that a 150amp fuse on a 100amp alt would offer almost no protection in the event of a voltage regulator failure. My EE friend tells me that European fuses will handle 95% of their rated capacity and that American fuse will handle 115%. Operating under the assumption that the maxi fuse I’m using is rated with the American system (I have not confirmed this) I would say that you want to match the nominal fuse rating to the max alt output. If you draw exactly 100 amps and your alt putts out exactly 100amp you would never blow a 100amp American rated fuse. That said I don’t think that I ever come close to pulling 100amp from my alt long term (only when recharging after a engine off drain) so I cannot back up the theory with real world experience. Another thing to keep in mind is that fuses time ratings are a curve. The fuse we are talking about may look something like115%=infinity then may go up to 120%=20min then 135%=1 min 150%=2 sec 200%=1/1000 sec.
 
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