What gauge wire for 24V, 72W, 8m extension RGBW?

Question

I have a simple question (I think) but I haven't been able to find the answer.

I have 4 * 5m lengths of RGBW LED lighting, which is rated at 24V, 14.4W/m. This is the maximum power draw, assuming the Red, Green, Blue and White LEDs are powered.

I have looked at the current / AWG table, and 22AWG, assuming rather pessimistically a 20core cable (I don't know what the core count is of the cable I could buy, so I'm erring on the side of caution here) is rated for 2.1A. I make that ~50W through one cable; given the highest draw for each LED strip would be 72W, this is around ~18W per channel, which is well below the 50W figure. What I don't know is what about the common (black) cable? Will that be needed to support the full 72W as it is shared between R,G,B and W?

In addition, would voltage drop be an issue over an 8m run of this cable?

I hope this makes sense - basically, if it's safe and won't cause problems, I would prefer to use 22AWG cable. However, would this be asking for trouble, and I'd be better off with 18AWG? (I want to avoid 18AWG if I can as it's far less readily available and significantly more expensive).

Thanks in advance. I hope that is enough information to help!

---EDIT---

The LED controller is: https://ltech-led.eu/en/d-series/1284-led-wand-controller-touch-d4-rgbw.html

It supports 4A per channel @24V for a total supply of up to 384W. I am intending to run four connections in parallel from the controller to the four strips (one run of cable per LED strip). I am using a 24V, 400W PSU designed for LED lighting.

The LED strip is this: https://www.led-lighthouse.co.uk/led-strip-lights/rgbw-led-strip-controllers/12v-rgbw-led-strip-lights-60-led-metre-ip68-nano-tech

I have 4 * 5m runs.

The PSU is connected into the controller, and then the LED strips to the output on the controller.

Answer 1

The issue is the current times the resistance per meter. 2.1 / n ohms = how much voltage will drop across it. Say 0.1 ohms per meter, 2.1 Amps / 0.8 ohms = 2.62 Volts. That section will drop the voltage your LEDs see to 21.38 volts.

Since your common carries the current for all of your channels, you must use the sum of all the current, for this section. Let's say 8 amps. That's 8 / 0.8 = 10 volts. So combined, 24 - 10 - 2.62 = 11.38 volts left for your LEDs. Of course the actual drop will be different because your LEDs will not have enough voltage to turn on so the current is less and the wires will not drop the same amount of voltage.

So grab the resistance per meter for a few different wire sizes and calculate what would be an acceptable voltage drop for your setup.

Answer 2

It depends on the supplier specs.

Some 24V RGBW specify 20 ft. max run or 6m max. So 8m would exceed this one. Often 1 or 2 reels(5m) is the max.

You will have to make other power feeds for cascaded LEDstrips beyond its rated distance.

14.4W/m *20m = 288W @24V = 12A

Assuming a 10% drop at the end of the cascade is acceptable drop in voltage.

To limit voltage drop for 10m 12A center feed with a 10% drop of 2.4V you can tolerate a resistance of 2.4V/12A = 200 mOhms or 20 mOhms/m and AWG 18 is ~21 mohms/m.

I would consider AWG 16 or AWG 14 household wire which all depends on the distance between supply, controller and center of two 10m strings.

Or as you said in comment below, 4 radial strips. If you need more distance than 8m, replace with heavier wire e.g. AWG 16 to 14. This is the total length from supply to controller to LEDstrips connections.