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300A Winch Fuse

ShadowsPapa

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Yes, thanks, you just supported both my earlier post...............

Just remember - under certain situations some winches will draw more than 300 amps.........
............as well as Russ's post about 300 amps being not enough for many situations.......

Yep, some as high as 465 amps.
It's one reason I don't have a fuse but chose the disconnect. Size the wire for more than the expected draw, even an unexpected draw.
Fuses are to protect wires.
Disconnects protect against the fool that runs into you or is higher than a kite on Johnnie Walker or whacky tobacky or some chick is texting her BFF about her date, and blows through a light as you reach the intersection.
No power up to the bumper, no worries about THAT aspect of things.

Fuses are good but must be sized correctly - and always carry a spare or three.
Breakers are good - but not as reliable as once they have been hot and tripped a time or two, they won't handle the same load. And if they are the automatic reset type, well, after they cool, you have that damn short again and again.
Breakers tend to take longer to trip - depending, and there are slow-blow fuses for when you need it to not blow too quickly, but still protect.
Breakers are good for wipers and headlights where you can't have a permanent dead item because of a blown fuse.
That's why auto makers have for many decades put breakers in headlight and wiper switches, and not used fuses. (there may even be a law about those two items - hmmm, have to dig into that)
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JWM PLAYS

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But you won't have the disconnect closed unless winching, so that doesn't wash.
The "dead short" would be while the winch was not in use, and while driving - times when the disconnect is open.
And a fuse will only blow when you reach its rating - in this case 300 amps. You can have a wear-through or a pinch that allows a lot of amperage, but not enough to blow a fuse, and still have trouble.
I've been in auto-electric for 50 years and I have seen cases where the fuse won't blow, but wires get hot enough to melt insulation and cause adjacent wires to melt or burn. It happens. In fact, a member screwed up plugging his trailer in and melted wires but never blew that 30 amp fuse on the 12v wire to the back.

The ideal is both. Fuse if you overload the wiring with a draw that's too high, and the disconnect to protect if you get hit while on the road.

My wiring is sized so that it will handle any normal winch use - up to the rated draw of the winch.
If the winch blows and burns out and pulls more than the wiring will handle, that's where a fuse would come in.
Otherwise, a disconnect has you covered for the entire time the winch isn't being used - which for most people is 99.99998% of the time.

I skipped the fuse because the only time there could possibly be an issue would be while using the winch - and with a new winch, and my likelihood of the winch drawing more than the wires can handle while I am using it is all but nil.

Kill the disconnect and then the one and only time you can have any issue is while actually using the winch - if you blow up the winch and it causes a dead short. But if you see the winch smoke or start to get hot - STOP! Duh. They'll take a heck of a lot of abuse but don't be stupid and stubborn and try to pull a 20,000 load with a 12,000 pound winch on the outer layer.
I see your point and it makes sense. You obviously have way more experience automobile electric than I do so I will defer to your experience. As a 30yr student of Ohms Law myself, the only part I can't wrap my mind around is having a short that carries enough current to burn the wires but not enough to blow the fuse. My experience though is mostly in the AC realm, not the DC. I'm guessing this comes about from a short that can pass say 200A for a extended period ultimately overheating the wire without ever reaching the 300A+ need to open the fuse? My assumption would be that during that failure, at some point the short would reach a low enough resistance to allow a large amount of current to flow thereby opening the fuse. As I type that though, I'm reminding myself that it's 12V pushing the current, not 277V.

As someone who performs electrical testing (AC) as a career, I can say to your point, it's worth noting that every "device" added to the circuit also adds more resistance and the opportunity for a device that has a bad connection adding much more resistance. I have equipment that I use to read resistance in the microohms range for verifying current paths in electrical circuits. Many times when we find high resistance in a current path, the source is a device such as overcurrent protection or a switch. That can collapse over time and actually become part of the problem rather than the solution.

Bottom line for me right now, the winch didn't come with anything so I'm happy to have the fuse on as opposed to nothing. You've given me pause however to considering a switch as well.
 
 



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