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I am planning to put led strip behind our false ceiling. It requires 50ft of LED strip. So planning to use 3 5M led strips of these (https://www.amazon.com/SUPERNIGHT-5-Meter-Waterproof-Flexible-Changing/dp/B00KNSO0M8/ref=sr_1_4?ie=UTF8&qid=1475628971&sr=8-4&keywords=LED%2Bstrip&th=1)

One thing that is concerning is the current drawn by these. It says each 5m LED strip consumes 6amps (2amps per color) so in total 18amps.

Does that mean i can't connect these strips to a 14-2 gauge wire which has a max 15amps rating. I also have other LED lights hooked on the same wire.

  • FYI, amperage and voltage are indirectly proportional to each other when resistance is constant. Meaning if one increases, the other decreases, – Kris Oct 5 '16 at 13:29
  • I think the biggest question here is WHERE do you plan on using the 14-2 wiring? On the AC or DC end? It seems there is some confusion over there. Please clarify – Joe Phillips Oct 5 '16 at 21:56
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It depends an awful lot what you are using the 14/2 wire for.

For 120VAC, and you want to feed all 3 power supplies

If you plan to use the power supplies that come with the kit, a 120V/15A circuit will supply those easily. They are 5 amps at 12 volt output (60 watts). Allowing for inefficiency, they probably draw 80 watts max on the 120VAC side. Three of them would be 240W, easily within the 1800W (120Vx15A) hard max on a 15A circuit. Like this.

enter image description here

All the DC wiring here can be 18 AWG except for the 120VAC wiring on the left, which must be 14AWG. You see why I don't like those power supplies?

However having worked with LED strips a lot, you are not going to be happy with the final result. You will have 3 separate installations of LED strip that will operate totally independently from each other and respond separately to commands from the remote. Not every controller will see every signal from the remote, so you'll never get the colors or brightness to match each other, assuming all 3 remotes are even compatible with each other (and not serialized). If you are rolling/cycling colors, the three strips will be out of sync. Try it for yourself, but I think it will find it frustrating, amateurish and dreadful, and you'll either rip it out in frustration, or look for a better way to do it.

For 12VDC to the strip lights

There are several ways to make an installation of this size work well. One is to power them all from a single larger DC supply, and have all that go through dimmers/amplifiers. Here on out I assume you have a larger 12VDC supply of your own.

The "standard" in LED strips is generally:

  • 12 volts DC

  • 300 emitters per 5 meters

  • 2 amps per channel per 300 emitters -- in a 3528 single-color strip, that's straight up 2 amps. 5050s have 3 emitters - commonly RGB but sometimes WWW (all three white). They have 3 channels, 2 amps per channel or 6A total.

Of course there are modifications on that. Double density or half density; 24V; coolwhite-warmwhite-yellow, just to name a few.

Your example seems to be a peculiar one. It's 5050, but they seem to be alternating RGB with WWW. They claim that the WWW can be controlled separately from the RGB (you would hope!) but that means they are doing something weird in terms of how the strip is wired. It is not 3 channels, it looks like 4.

But since half the total lights are on the "white" chanel, half the 6A power is on that channel, or 3A per strip. The three RGB channels split what remains, 1A each.

Power all three strips from one supply

Three strips together would be 9A on the white, 3A on each R/G/B color, or 18A for any feeder wire that is handling all the power for all of them. Also, 18A on the return ('neutral') wire.

enter image description here

The 120VAC wire must be 14AWG. The feed between power supply and controller must be 12AWG (14AWG would not suffice - I believe that was your original question.) If any distance is involved, go10 AWG and you'll want stranded wire so it's more flexible. The return back from the strip must also be 12AWG and the "white" wire must be 16 AWG or larger. Color wires can be 18AWG or larger.

Since you're working in DC power, there is no requirement to have the "return" wire run in the same cable as the "supply" wires. So you could use 14/4 for the supply to all 4 colors, then run a single-strand 12AWG wire for the return. Or 12/2 for the white and return, and 18AWG thermostat wire for the rest. Since it's low voltage DC you are not obliged to use white/blue for neutral and green for ground.

Another option is do a separate "homerun" for each 5-metre strip, so the return would be only 6 amps, which would permit you to use 18AWG intercom wire of however many strands you need.

One controller, three power supplies

You could power each strip separately, and control them centrally using amplifiers. To do this, assemble each LED strip in the normal way, but use an amplifier where the controller would go. Then use one controller, and split its R G B W and common wires to each of the amplifiers. This means all three strings will be the same color, do the same patterns, etc. You will end up with 2 spare controllers, but you will have to buy 3 amplifiers.

enter image description here

All the wire can be 18 AWG here except for the 120VAC wiring which must be 14AWG. The wires to the controller draw very low current, but wire thinner than 18AWG isn't any cheaper.

(it's possible to hook up one string normally and use amplifiers only with the other two. I don't recommend that, it'll be hard to troubleshoot, and the strings will not be equal.)

  • 14-2 wire is for 600VAC though... – Joe Phillips Oct 5 '16 at 21:18
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    It wouldn't matter if you used 25,000 volt wire. 14AWG is too small for 18A. Lowering the voltage does nothing to increase ampacity. – Harper - Reinstate Monica Oct 5 '16 at 21:25
  • You're missing the whole point. 14-2 is rated for AC (120 volts) whereas the you're looking at DC (but likely coming up with the wrong numbers). You can't just willy nilly convert between the two without accounting for the voltage change. Read my answer – Joe Phillips Oct 5 '16 at 21:30
  • /facepalm Nobody's willy-nilly converting. I don't see where 120VAC ever entered the discussion. Since this seems to be a confusion I modified my answer to head it off. – Harper - Reinstate Monica Oct 5 '16 at 22:03
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    It's quite possible OP himself isn't clear. In any case, in an LED installation like this, 14/2 does not imply 120VAC, it is perfectly acceptable to use 14/2 to wire 12VDC circuits. – Harper - Reinstate Monica Oct 5 '16 at 22:07
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It says it uses 12W/m @ 12VDC or 5A of current for the 5m roll. That means at 120VAC you 'll be pulling 0.5A of current per roll (not the 2A Joe said because he swapped the numerator and denominator). So your total draw for 3 rolls is 1.5A. This is of course ignoring any losses, spikes, etc.

  • Your answer is correct for the AC-fed power supply that comes in the kit, but on an installation this size he may not be using it. I would factor in 30% for inefficiency. However these strips are inherently 12VDC devices and the amperages he names in his question are relevant to the 12VDC wiring from the power supply to the strips proper. – Harper - Reinstate Monica Oct 5 '16 at 22:44
  • @Harper Yes, my answer is for plugging the 3 power supplies into standard 120VAC outlets. – topshot Oct 5 '16 at 23:22

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