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Old 04/12/2019, 03:20 PM   #1
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How many amps for 18awg wire for LED setup?

If someone with electrical knowledge a bit more than me can chime in to check my reasoning/logic.

So I have these dead DC pumps + controller, and I love the connectors on them, little water tight ones with 3 prongs that screw together. Figure I'd just use that as power cables from my Meanwell PSU to the LEDs.

There are 3 wires in cable, 18 gauge is my educated guess, guessed this because the 16awg notch on my wire strippers don't pull off the insulation, but the 18awg notch gets it off cleanly.

Now I want to daisy chain two fixtures to the same cable, and wondering about load limits of this wire, I've seen everything from 16 amps for chassis wiring, and 2.4 amps for power transmission, now I'm not an engineer just a physicist but I'm not sure what to make of this.

Now each fixture has 2- 1000mA and 2- 700mA Meanwell LDD drivers, so I figure it's pulling approximately 3.4A through the circuit, then 2 of fixtures so 6.8A total (roughly). This is where the chassis designation vs power transmission gets me. I'm guessing chassis is for relatively short distances of wire possibly in the 5-10ft range, where as power transmission might be for the 100 ft+ range? Now the wires will be anywhere from 6-12 feet (double that for the round trip).

So am I in trouble with using a single conductor for the hot and neutral? If so would I be ok with using all 3 conductors in the wire for hot, and another 3 in another for neutral? Or should I just not risk it? I mean I can get UL-listed water proof connectors at the big box store that are rated for 10A and just use some 12-gauge stranded and call it a day, but if I can get away with this thinner stuff it'd make my life a lot easier.

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Old 04/12/2019, 08:24 PM   #2
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#18 is geneerly used for control wiring and speaker wire. It can handle up to 10A of low volltage, but it’s not not rated to be “permently installed.”

Meaning you could use is as a plug in cord, but it should’t be fixed to a switch or breaker.

Just because the wire can handle 10A doesn’t mean the sheathing can. It could run hot over 5-7A.

I’d go with #14 if it was me....

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Old 04/15/2019, 11:21 AM   #3
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There is a calculator at the bottom to help you determine this.
NOTE though that specs are extremely conservative....

Guess the toughest part is the fact that voltage will vary as the driver bucks the power supply output..

There are probably 1/2 doz itty bits to add to this calculation..
like if you can "accept" a 2% voltage drop (and accompanying heating) @ 12ft to the ldd
Or solid vs stranded
supply voltage
Pulsed drivers (are they usually "dimmed" )ect..
The Maximum Amps for Power Transmission uses the 700 circular mils per amp rule, which is very very conservative. The Maximum Amps for Chassis Wiring is also a conservative rating, but is meant for wiring in air, and not in a bundle. For short lengths of wire, such as is used in battery packs you should trade off the resistance and load with size, weight, and flexibility. NOTE: For installations that need to conform to the National Electrical Code, you must use their guidelines. Contact your local electrician to find out what is legal!

At that length I'd probably not recommend 18ga..
16ga "may" be sufficient.. based on the conservativeness of the ratings..
and if ANY recommendation was made.. that would be it.. 16ga..
18ga would be fine w/ this calculator..

and of course jacket material needs to be considered..

sorry not really an answer..

One more w/ metric conversions..

Last edited by oreo57; 04/15/2019 at 12:03 PM.
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Old 04/15/2019, 04:16 PM   #4
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18AWG can handle 8-10Amps without issue..
16AWG can handle 15 Amps without issue..
Speaking from professional/hands on experience

Being blunt and having fun
Straight up INTJ
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Old 04/16/2019, 04:32 PM   #5
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Ok, currently running 200 watts at max settings with my LEDs (and the fans and driver... too lazy to plug each one into a KAW meter). So that's a little over 4 amps when it's at max power, which at current ramping settings is about 6 hours a day. Cord feels fine, not warm at all, so I'm happy with it for now.

Little more comfortable with the fact that the connectors are those screw together water tight connectors, my first run through with this quite a few years back I was using brass connector plates with copper wiring, galvanized screws and completely ignoring the whole galvanic corrosion issue... little more on top of things now. But glad to know it can handle the current.

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