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I built a new deck and I'm installing 3/4" EMT with raintight connectors to power an outlet and a couple of low voltage 12VDC LED drivers beneath the new deck. Each driver has a built-in junction box with one knockout on the left and one knockout on the right. The drivers look like this:

enter image description here

As you can see, the pigtails for the 120V inputs and 12VDC outputs already share this junction box.

I am running separately switched and dimmable power to each driver.

Is it OK to wire the two drivers as shown below so that I can use a single, straight piece of EMT, along with a short 2" stub between the drivers, or does the fact that I will have 12VDC in the same, short 2" piece of conduit violate code?

Thanks!

Joe

Original Diagram Original Diagram

Supplemental Diagram - NM CABLE OPTION #1 (for discussion) enter image description here

**Supplemental Diagram - NM CABLE OPTION #2 (for discussion) enter image description here

UPDATE: This is how I installed per comments below. Thanks!:

enter image description here

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    Is the 12VDC power staying in conduit (or another chapter 3 wiring method, such as UF cable) all the way to the loads?
    – ThreePhaseEel
    Commented Jun 25, 2021 at 11:27
  • No, I'm planning to use 12/2 direct burial landscaping cable to bring 12v to a few path lights, a few floods to light a wall, and a few hung lights supported with an aviation cable.
    – JoeA
    Commented Jun 25, 2021 at 11:43
  • I take it your "direct burial landscaping cable" is CL2 by another name?
    – ThreePhaseEel
    Commented Jun 25, 2021 at 11:47
  • Not sure on the CL2. This is what I plan to use for the 12v: cerrowire.com/wp-content/uploads/2019/12/…
    – JoeA
    Commented Jun 25, 2021 at 13:58

2 Answers 2

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Basically your power wires between the power supplies would need to be NM if "Dry" location or UF if "Damp" location, and the conduit would be big enough to satisfy conduit 60% fill limitations, and likely an inspectors interpretation might not allow the low voltage wire from the first power supply in the second transformer junction box.

Your Power Supply says CL2 on the label, and if your location is subject to the NEC then must be installed according to Article 725, Part III where it says:

725.136 Separation from Electric light, Power...

The line side of your power supply is Power.

725.136(A) General. Cables and conductors of class 2 and class 3 circuits shall not be placed in any...enclosure...raceway...unless permitted by 725.136 (B) through (I).

Sections (B) through (I) are titled; (B) Separated by Barriers, (C) Raceways Within Enclosures, (D) Associated Systems Within Enclosures, (E) Enclosures with Single Opening, (F) Manholes, (G) Cable Trays, (H) Hoistways, (I) Other Applications.

You likely don't satisfy (D), but can meet (I).

(D) Associated Systems Within Enclosure ... where introduced solely to connect the equipment...

Your wires are passing through, that doesn't fit the description as solely.

(I) Other Applications... shall be separated by 50mm ... unless one of the following conditions is met: (1) either all of the ... power or all of the Class 2 ... are in a raceway, metal sheathed, metal clad, non-metallic sheathed, type TC or type UF cables (2) ... are permanently separated ... by a continuous and firmly fixed non-conductor...

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  • So are you advising OP to use a NM cable inside the conduit between the boxes? That's what it sounds like would satisfy (I).
    – Harper - Reinstate Monica
    Commented Jun 25, 2021 at 17:49
  • Thanks guys. Would either or both of the "NM Cable Options" I posted above work?
    – JoeA
    Commented Jun 25, 2021 at 19:37
  • Inside conduit in damp/wet location is still damp/wet, even inside conduit, so if damp/wet location you would need to install UF inside the conduit. The only section of conduit at issue is the small piece between power supplies.
    – NoSparksPlease
    Commented Jun 25, 2021 at 22:25
  • Got it. So, "Cable Option #1" would be sufficient with the NM ("Romex") replaced by UF. Thanks.
    – JoeA
    Commented Jun 25, 2021 at 22:58
  • Out of curiosity, now that I'm reading the whole NEC section, might it already be sufficient to stick with THHN-THWN wires and then, under 725.136(I)(2), regard the insulated jacket on the 12V cables as "a continuous and firmly fixed nonconductor, such as .. flexible tubing, in addition to the insulation on the conductors?"
    – JoeA
    Commented Jun 25, 2021 at 23:06
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As long as your low voltage cable is rated for the maximum voltage of the power conductors it will be fine.

The landscaping wire i use is. I thought it was 300v but it may be 150 like yours. I have done this when enclosing transformers and running things to a outside location.

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    +1 - it's all about ratings. I even have data cables (ethernet) inside a cabinet with 1600A/600V switchgear, for example. The ethernet cable in that case has to be 600V rated - it's fat, expensive, and has thick, crush-resistant insulation, but it's what you need for the job.
    – J...
    Commented Jun 25, 2021 at 15:27
  • Yes. I support similar 480 equipment with 1200hp being controlled by a PLC with 24v control but I use 600v insulated wire and cables.
    – Ed Beal
    Commented Jun 25, 2021 at 17:08

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