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  #31 (permalink)  
Old 09-13-2011
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This is really interesting...and a bit distressing because the amp ratings on these things seem to be largely meaningless. Why not call a 300 amp fuse a 300 amp fuse???? It seems a little silly (and dangerous) to call a fuse that will NEVER blow before 440 amps a 300 amp fuse. I have always ass-u-med that these physical fuses, in contrast to a circuit breaker, would be MORE accurate when matching wire sizes to circuit protection. It's like saying it's ok to put a 30a fuse on a #12 wire in your house--not a good idea.

The starter on my Yanmar 3GM30F has a current rating (from service manual) of "460a. or less" under a load, although looking at the torque curve, it appears that above 8v. it would never draw>350a. Even a 400a fuse would be cutting it close which is why I have a 500a ANL in place at present which will , in actuality only help for a dead short. Now...if a 500 amp fuse is ACTUALLY a 600 amp fuse, maybe I can knock it down to 400 amps (or even 275 if the chart is accurate), still well above 2/0 wire ratings but a bit less likely to melt off insulation in a partial short.

This is all a good reason to use additional conduit (as I mentioned above) to protect starter wires. If these things weren't so expensive, I'd like to experiment with them to get some real results.

Last edited by smurphny; 09-13-2011 at 01:22 AM.
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Old 09-13-2011
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With starter wiring you are really fusing for short circuit protection - and in that case the fuse will blow. I don't think overload is an issue as the starter is only used for 5 or 10 seconds at a time. The same really goes for main battery fusing as well.

Like Maine I have blown an ANL fuse by mistake. Did just what it was supposed to do.

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  #33 (permalink)  
Old 09-13-2011
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Quote:
Originally Posted by mitiempo View Post
With starter wiring you are really fusing for short circuit protection - and in that case the fuse will blow. I don't think overload is an issue as the starter is only used for 5 or 10 seconds at a time. The same really goes for main battery fusing as well.

Like Maine I have blown an ANL fuse by mistake. Did just what it was supposed to do.

From Blue Seas:
My sentiments exactly. That's why I have the starter fuse well over sized: In case I drop a wrench across or something breaks and spans across + to -. Pretty much any fuse will blow in those situations if physically smaller than the wire.
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