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. Hey, all!

Wondering, if I am running three sections of LED lighting from a single transformer, would the following be an appropriate solution? I would run a single NM-B line from the dimmer to the transformer. Then, I would make a short run of CL3 in-wall wire from the transformer to a splice box. Then, run three separate CL3 lines to each of the strip sections. Inside the splice box, I would join all the negatives and positives via something like Wago 221 5-pin connectors.

That seems like what, say, Waveform Lighting's article about it suggests, though they recommend a screw terminal. They also explain how "series" or "parallel" are a bit of a misnomer with LED lights. I just wanted to confirm before I go closing up walls.

For the reference, the kind of LED strip I am considering just comes as a 16-foot roll and then you can slice it into whatever lengths, as far as I'm aware.

Thank you!

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  • I'm concerened that you're stating that you're putting a dimmer in front of the transformer. Is your transformer rated for dimming? If not, then I highly suggest you rethink your solution. But any 120V power (assuming you're in the USA that uses 120V) needs to be done to code, and any 120V connections need to be done in an approved manner.
    – Milwrdfan
    Nov 24, 2023 at 20:36
  • Yep, it's a Triac dimmable "driver." Perhaps transformer was the wrong word. It converts 120v to 12 or 24v, depending on the model; 24v in my case
    – Zoinks
    Nov 24, 2023 at 20:54
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    Yes. Parallel connection is the way to go. Join all the positives, and (separately from the positives) join all the negatives, and you're good to go. If you didn't buy the power supply and strip together, then add up the current/power consumption for each strip section, and ensure the total is less than the maximum the driver is able to deliver. Nov 25, 2023 at 10:58
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    Aside: Long strips may suffer from internal voltage drops that cause one end of the strip to be visibly dimmer than the other. The effect can be reduced by connecting both ends of the strip to the power source.
    – HABO
    Nov 26, 2023 at 1:15
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    Zoinks - I don't think you'll have any worries at those kind of lengths. You can buy this strip by the hundred feet; that's when you are likely to see issues with voltage drop.
    – Tetsujin
    Nov 26, 2023 at 10:02

1 Answer 1

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LED strips are always parallel; that's just how they're built. Joining the end of one to the start of the next is still parallel, even if you think it may look like series. They're just parallel rails with LEDs strapped between, like a ladder.

That's why you can cut them every few inches, at the copper dots; they're just a strip of identical modules with a rail down each edge. They don't care how many are in a strip or how many strips there are.
The only thing that cares is the PSU*, which must match for voltage & have equal or greater amperage than the total power draw.

So you can run a pair of wires to one end of each strip, or run each strip out of the end of the last - there is no difference. Just observe polarity, positive to positive & negative to negative every time. You don't need to complete a loop of any sort; your end point in every case stays open.

*A PSU [power supply unit] is a set of electrical components containing amongst other things a transformer, but a transformer alone is not a PSU.

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