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...The Project...

Install 94 feet of perimeter lighting around a kitchen/dining/living space. The desired product is a color tunable LED strip. Possibly this product but I could use an equivalent product if needed. These things come in 16 foot lengths. So I need 6 strips to cover the installation.

Wiring

I have roughed in seven 16/4 CL2 rated wire to the top of the wall at locations where each 16 foot strip would start. The led strip product indicates that two strips can be chained together, but that seems like a voltage drop risk, so I ran a separate wire for each strip.

PWM Dimming

High frequency > 25kHz PWM dimmers are the only acceptable option for this requirement. We tested the 500hz LED dimmers and they had noticeable flicker at low light levels. There are several DMX decoders that meet this need. For example, this product.

Power Supply

Here is where the going gets tough. How do you meet class 2 power supply requirements for the installation of these products? NEC 725.121 "Power Sources for Class 2 and Class 3 Circuits" seems to require a listed class 2 power supply. Does that mean I need six separate class 2 power supplies, and six separate DMX decoders... One for each strip? That seems wasteful as a single DMX decoder is capable of 8 amps per channel and could power the entire set of 6 strips by itself.

Are there any other options for a compliant installation?

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Note The (4) and (5) options of 725.121 are Information Equipment, and a dry cell battery. Neither of which meet this need.

  • 725.41 is class 1 at least in the 2017 & 2020 code class 1= 30v 1000va or less that would be a max of 33 amps. I think I remember landscape lighting 12v limited to 25 amp. Could you double check that is the issue you are looking at. – Ed Beal Mar 16 at 16:39
  • @EdBeal I think I was looking at some old code blogs... you are correct. The area in 2017 code is 725.121. I have edited the post. – Anthony Vito Mar 16 at 17:44
  • About 10 times the price I'm used to seeing for an LED strip. Might be worth it if UL listed. Why /4 wire? The strip has 3 conductors. You don't need seven "home-runs" if you can tie to the wire. You could do with as few as three tie points, between strips 2-3, strips 4-5, and strips 6-1, and feed each strip from opposite directions. In fact this would be better to assure no visible effects of voltage drop. This advice applies to 24V strips. For 12V strips I'd feed every strip from both ends. Also you know this is 23A worth of strips, right? Dimming that takes planning. – Harper - Reinstate Monica Mar 16 at 21:20
  • @Harper-ReinstateMonica The strips are fairly high quality. If you know of any >95CRI color tunable strips pushing over 400 lumens per foot let me know! I could only find a few options and they were all about the same price. This particular product is not UL listed. I used 16/4 because it was readily available in CL2 rated form. The "home-runs" are already installed. They are overkill but offer flexibility in zoning. Many single DMX controllers can handle dimmer the entire set.... My concern is being outside of class 2 code on the power supply end. – Anthony Vito Mar 16 at 23:42
  • @AnthonyVito -- have you checked Table 11(B) in Chapter 9 of the NEC? That's where the limits on what a listed Class 2 supply can put out are found – ThreePhaseEel Mar 16 at 23:43

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