Wire size help

[Stomper]

I picked up 2 led light bars, one for forward and one for reverse. I am also converting my 3PH snow blower over to electric for the chute deflector and rotation. I am also installing a electric 3rd function valve for a future grapple. I had the space in my existing fuse block but there wasn't any connections in the spots where the fuse would go, so I picked up a 6 gang fuse block that I will install for the added equipment. There will be three electric circuits at the back of the tractor with each controlled by their own switch and fuse, each light bar will have its own switch and fuse and the 3rd function will have its own switch and fuse. I will run power from the battery to the fuse block with a fuse as close to the battery as possible. From the fuse block I will supply each circuit. For the power supply to the back of the tractor I will be using a 6 way trailer plug to keep things neat and tidy.
To determine the wire size and fuse size from the battery to the fuse block do I add up the operating amps of each electrical component and go with wire rated for the combined amps of the equipment

 

[George2615]

If it were mine I would run a 10 gauge wire from the battery to feed to fuse block. Then run 12 gauge wire from fuse block to each circuit you want to add and install 20A fuses in the fuse block.
I am not an electrician but I doubt any of the items you mention are going to draw close to 20A and could be run at the same time. Check the paperwork that comes with each item for amp draw. You may be able to use 10 or 15A fuses instead of 20A.

 

[powerscol]

George gave good advice. I also used 10 gauge with a 30 amp fuse at the point of power which in my case was the positive started lug. However I put my primary wire in a wire loom to protect it. My circuit block was wired with 12 guage and fuses were per the rating of the item being installed recommended. All wires were put in wire looms for protection. Most were 10A for a 5 amp draw. If I have everything on - which is probably not going to happen in my case I only draw 25amp, so yes add up all the draws and fuse accordingly, but give a 5 amp margin.

 

[Stomper]

Just what I was wanting to hear. Thanks guys

 

[Fallon]

Wire Size Calculator

Always make sure the voltage drop is as low as possible. 2-5% or less if possible. Always make sure fuses are rated less than the wire. You want fuses to melt, not the wire.

 

[Stomper]

Never thought of it that way about the fuse size but it makes perfect sense. Thanks fallon

 

[Fallon]

Never thought of it that way about the fuse size but it makes perfect sense. Thanks fallon

Yup. That's the whole point of a fuse (or circuit breaker). It's to protect the wiring & hence the vehicle/house/whatever from burning down. It's not to protect whatever is connected to that wiring.

 

[Dave Pee]

"It's not to protect whatever is connected to that wiring." Also very true with electronic loads - the electronics will self destruct long before a fuse pops.

 

[davedj1]

12 gauge seems a bit overkill for a third function switch and some LED's
Think about this, 40' fifthwheel campers only have 18 gauge to run clear to the back of them for the tail, stop and turn lights. I doubt in a tractor application you will have much more than 8' of wire. Size according to your load, not according to what you "may" have. If you have too big of fuse you could potentially burn a wire and possibly burn down the tractor if something were to go wrong. 75 watts is only 6.25 amps so take that for what it's worth. But then again you didn't say what light bars you bought.
Here's a neat fuse block that goes directly on the battery: Blue Sea Systems ATO / ATC Fuse Block - Battery Terminal Mount

 

[Ken Kegris]

10 gauge wire is a good choice for the battery to fuse block and 10 gauge is rated for 30 amps 12 gauge wire is rated for 20 amps and 14 gauge for 15 amps. I would install everything then using a amp-probe see what each item is drawing and add about 2 amps to that figure and fuse at that figure. Its always better to wire heavy and fuse light. I agree putting wire in wire loom is a good choice wire can rub through rather quickly on a vibrating tractor, Use good crimp on connectors with soder and good heat shrink instead of tape, makes a neater job and looks more professional.

Kenny. kkegris@yahoo.com