Going to run 6 circuits to the back of the truck - one shared ground wire?

I have a switch pros and will plan on running ~6 low amp draw circuits (like 1-4 low amp led lights per) to the rear of the truck. I am future planning a little and won't need that many right away or probably ever.

I am planning to just create one big harness in a sleeve and have it ready for whatever I need. I am going to run (6) 14AWG wires and was planning on (1) 10AWG ground wire all the lights can tap into. Is 10AWG enough for a common ground like that?


Looking at the following possible circuits:
(4) KC 3" C-SERIES C3 LED PODS at the corners of the bed rack
1.0A draw each / 4A total
https://www.kchilites.com/3-c3-led-pair-pack-system.html

(4) Amber KC 2" CYCLONE LED LIGHT as bed rack "dome lights"
.42A each / 1.7A total
https://www.kchilites.com/2-cyclone-led-light.html

(3) Baja Designs S2 Sport, LED Work/Scene, Amber in the rear cutouts of the Rago bed rack
.9A each/ 3.6A total
https://www.bajadesigns.com/products/S2-Sport-LED-Work-Scene-Amber.asp

 

If they’re all controlled by the same switch it won’t be a problem but if they’re individually controlled it could cause problems if you only turn on specific ones at a time. You should use multiple grounds

 

Those circuits do not appear to be critical, I see no issue with it in general.

Without running hard numbers, looks live voltage drop will not be excessive, and there is ample ampacity (even in a bundle thru engine compartment). **Did quick numbers below

I think more importantly, what you really need to consider is failure modes and effects.
You will now have a single point failure for all these circuits. That ground fails you loose all the circuits... Is that a concern?
Also consider that a failure of the ground CAN apply positive voltage to the ground side of other unpowered circuits... Probably not a concern, but can cause issues and weird things depending on the item.

All that said, I would bet there is no strong reason to run a separate ground, with these low current items. (very high current items you definitely want to run a separate ground, these don't qualify as high current items.)

Some numbers thrown together, needs to be doublechecked
Using ABYC data, just for simplicty 21731.pdf (bluesea.com)
Voltage Drop Assume 25 ft outgoing, and 25 ft returning (sounds very conservative)
(No this isnt a requirement for your truck, but its handy to run the numbers)

14 AWG ~= 2.63 ohm/1000 ft
10 AWG ~= 1.04 ohm/1000 ft

Voltage drop for 1 Amp @ 25 ft for 14 Awg
V(14 AWG)=.00263 ohm/ft * 25 ft * 1Amp = 0.066 V

Voltage drop for 9.3 Amp @ 25 ft for 10 Awg
V(14 AWG)=.00104 ohm/ft * 25 ft * 9.3Amp = 0.242 V

Total Voltage Drop = 0.066+.242 ~= 0.31 V

For non-critical loads, normally 10% voltage drop is allowed, 3% limit for critical loads
.31V/12V = 2.6%, so your wiring meets critical criteria, and is very ample for non-critical criteria (for voltage loss).

For ampacity, lets assume that you are using 75C wire, in a bundle of 7 wires (7-24), in engine compartment (0.714 knockdown)
14 AWG ~= 15 amps * 0.714 = 10.71 ampacity
10 AWG ~= 30 amps * 0.714 = 21.42 ampacity

So voltage drop is less than typical requirement.
And amp capacity of the 14 AWG and 10AWG is ample.

Make sure you fuse the wires.

 

Your ground would be more than adequate, but why not use a grounding point already at the back?

 

Running shorter and then smaller ground wires the the frame/chassis points in the rear will cause less overall resistance for your circuit. You already have grounding points for all of the factory electronics in the bed, lights, trailer harness etc

 

3rd Gen has a consolidated ground at the rear (just one).

 

Where is that?

 

I'm confused why not just run a self tapper into the frame as your ground?

 

Self tapping into raw steel, add vibration, get loose screw, then add moisture, get corrosion, = bad ground.

Usually better to use a pre-existing ground hole that has tighter threads, so you can clamp it down tightly.

 

Makes sense, but I've yet to have one back out though I normally paint over it.