What amp fuse?

[imported_JD__]

I've mounted a 100 watt halogen running/fog light to the front of my boat for night fishing. For power, I've come off the accessory (purple) terminal side of the ignition switch, same place where all the gauges are daisy-chained.I have spliced in an in-line fuse holder between the switch and power. Is this OK or should I go to the main fuse panel? What amp fuse should I use?

 

[crab bait]

Re: What amp fuse?

every accessory should/must be overload protected/fused..<br /><br />15 amp would do just fine..<br /><br />see,, rule-of-thumb, anything that is electronic should be fused at manufactor's specs.. an that's to protect that expensive piece from ruin..<br /><br />but any non-electronic device,,can be over fused somewhat.. as your only protecting your wiring from meltdown an fire.. mostly from a shortcircut..<br /><br />10amp mite do.. i'd go 15 amp..

 

[18rabbit]

Re: What amp fuse?

What Crab Bait said, and ...<br /><br />You can take the watts (100) and divide by the volts (12) to get the amps...in your case about 8.3amp, so a 10amp fuse will be fine because a light bulb doesn't have a startup in-rush of current like a motor. If you had a motor, then that 15amp fuse would be necessary.

 

[imported_JD__]

Re: What amp fuse?

Thanks guys, I really appreciate it!

 

[imported_JD__]

Re: What amp fuse?

Thanks guys, I really appreciate it! This just goes to show you can teach an old dog new tricks.<br />I wasn't aware of the formula, wattage divided by volts = amps. I will remember this.

 

[Silvertip]

Re: What amp fuse?

It's called Ohms law. If you have any two values of power (watts) voltage, resistance (ohms) or current (amps) you can find the third value.

 

[jlinder]

Re: What amp fuse?

I would also point out that if you have a 15 amp fuse you would need to make sure that the wire you ran is at least 14 ga. <br /><br />That is what is needed for safety. When you pick a wire size you also need to look at the voltage drop caused by the wires.<br /><br />Take the current draw (8.3 amps in this case), the cable length, and the wire gauge into account and you can calculate the voltage drop. There are lots of calculators for this on the web and if you search this forum for voltage drop and calculator you will find the links.