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Wire gage for 5x LED lights

2K views 6 replies 4 participants last post by  whitexkr 
#1 ·
About to custom wire the lights listed below on my roof basket.

Rough Country - 70806 - 6-inch Chrome Series Adjustable Base Mount CREE LED Light Bars (Pair) 60 watt
Rough Country - 70903 - 2-inch Chrome Series CREE LED Square Lights (Pair) 36 watt
Rough Country - 70930 - 30-inch Dual Row Chrome Series CREE LED Light Bars 180 watt

Planning to run 1 ground and 3 powers from the lights down the side rain channel on the rear hatch to the undercarriage. Ground taps to the chassis in the rear and powers run down undercarriage to relays/battery underhood. Then switch runs from relays through firewall boot to cabin.

My big unknown is what gage wire I need for the ground and 3 power leads. 276 total watts output (60/36/180 watts respectively) and no listing of amps. Also what amp fuses on the power leads. Want to go as small as is safe since the entry gap between the top of the hatch and roof isn't huge.
 
#2 ·
Amps = Power/Voltage. Assume 14.5 for the voltage. So for 60 watts, you have about 4.1 amps. Fuse that at about 2x max., so a 7.5 amp fuse is a good choice.

For 36 watts, fuse at 5 amps

For 180 watts, fuse at 20 amps.

Here is a website that will give a minimum wire gauge. You need to estimate the length of the run to get a good number. Wire Size Calculator
 
#3 · (Edited)
The fuse size is dictated by the wire capacity, NOT load. They are to protect the wire only and not the device.
For example:
The 180 watt bar will likely require a 12 gauge power feed since it pulls around 12 amps. If the wire is no longer than about 11 feet the current carrying capacity is about 15 amps. The correct fuse size is 15 amps. If the correct fuse size is not available (say max current capacity is 13 amps) then your fuse size is stepped down to 10 amp because there is no 13 amp fuse available. Alternatively, you can increase the wire size to the appropriate size for 15 amps at the length of wire you have.

BTW, for that kind of wattage those don't throw very much light farther than your headlights. They are bright, but not much distance to them.
 
#5 · (Edited)
True, that ultimately the primary purpose of the fuse is for protecting the wiring, but you certainly cannot ignore the load and go to a fuse below the rated load. My post above provided a link for correct wire gauge determination.

You also need to fuse with a margin above the rated load (typically 1.25x to 2x) to avoid nuisance blowing due to inrush currents from power supply capacitors with electronics or inrush currents with incandescent lamps.
 
#6 ·
Of course you can't go below the load of the lights but you have to protect the wiring. True, there is some inrush for LED but not incandescent loads. Resistive loads do not have inrush current like a motor, capacitor or ballast
 
#7 · (Edited)
True, there is some inrush for LED but not incandescent loads.
Incandescent loads do not behave like fixed resistors. They actually have very low resistance with a cold filament and the resistance rises when the filament heats up. They have a large inrush current.
 
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