120V to 12V Wiring for LED Lights in Custom Built-Ins

[Phil in NC]

Hey all:

I am planning to build built-ins in my home office, and I want to put LED strip lighting under the cabinets and some of the shelves.   This is my plan for the builtins:



So I plan to use some Hitlights transformers that allow you to control the dimming of the low voltage LED strip lights with a standard dimmer switch.  The link to these transformers are here:

https://www.amazon.com/HitLights-Dimmabl...ransformer

Here is the image showing the wiring diagram for hooking these up:



Here is a description and close up picture of what I plan to do:

Make a male plug with a 2 conductor + ground wire going from the outlet to the junction box.   From there the hot leads (black) will go up to the switches.   The ground (green) and neutral (yellow) leads will go into the transformers.   The hot leads from the switches (red) will go back down to the transformers.   From here, the transformers will put out the dimmable low voltage leads for the LED strip lights.  



My questions:

The hot leads will be going from the junction box up through a hole in the counter top then between the two shelf walls where the switch boxes are.  This is about a 1.5" gap between the two shelf walls.  The dimmers will be in a standard plastic old work shallow electrical box.

What kind of wire should I use here??   I don't think Romex is supposed to be used outside of walls, per NEC.   

Is a special kind of wire required since it will be in a narrow gap between two pieces of plywood??  

Also, since the transformers are only rated to 80 total watts (combined), which doesn't even pull 1 amp at 120V, I am assuming that I can use 16-18 gauge wiring.

Thanks in advance for the help...  I want to make sure that I am doing this right, and I have not been able to find anything about what kind of wire to be used within wooden built-ins.

[EricU]

I would repurpose a computer cord from the outlet to the junction box, and after that use lamp wire.  If I read you right, all of this is going to be plugged in, not hard wired, so I wouldn't worry about code too much, just safety.  This is what I did with my under cabinet lights in my kitchen.

[Phil in NC]

I would repurpose a computer cord from the outlet to the junction box, and after that use lamp wire.  If I read you right, all of this is going to be plugged in, not hard wired, so I wouldn't worry about code too much, just safety.  This is what I did with my under cabinet lights in my kitchen.

You are correct, this will all stem from a plug in the wall, not hard wired.  

I just didn't know if having the wires going up to the dimmers with 120V (and very low Amperage) would be a problem in between two narrow wood shelves.  

Thanks,  Phil

[Roly]

You are correct, this will all stem from a plug in the wall, not hard wired.  

I just didn't know if having the wires going up to the dimmers with 120V (and very low Amperage) would be a problem in between two narrow wood shelves.  

Thanks,  Phil

Just so you know it is not anywhere close to code.   Lamp cord cannot be run through a wall even if it is plugged in,  the 120v dimmers are hard wired and the yokes should be grounded.  Roly

[Phil in NC]

Just so you know it is not anywhere close to code.   Lamp cord cannot be run through a wall even if it is plugged in,  the 120v dimmers are hard wired and the yokes should be grounded.  Roly

None of this wiring will be behind or inside a wall.   It will all be inside the cabinet and the hot leads to the dimmers will be run through the built-ins between the plywood towers where the switch boxes will be.  

The manufacturer of the transformers shows in their instructions that only the hot leads need to go to the dimmers.   The ground and neutral can go directly from the power source to the transformer

LED strip light transformer

[Roly]

None of this wiring will be behind or inside a wall.   It will all be inside the cabinet and the hot leads to the dimmers will be run through the built-ins between the plywood towers where the switch boxes will be.  

The manufacturer of the transformers shows in their instructions that only the hot leads need to go to the dimmers.   The ground and neutral can go directly from the power source to the transformer

LED strip light transformer

Look up the wiring instructions for the 120v dimmers. Do they have a grounding terminal ? Besides a ground some may require a neutral.   Roly

[EricU]

I'm sorry about my previous answer, I was careless about looking at your schematic.  I only use lamp wire on the low voltage side.  A 120v dimmer should be fed with the correct ampacity 3 or 4 conductor wiring, as appropriate. I know there are dimmers that take a neutral, but they aren't particularly easy to buy.  I have a problem circuit with Leviton digital dimmers that I suspect would work a lot better if I could buy the ones with a neutral

[Mr_Mike]

Just because I overbuild...

I'd use BX wire and metal boxes on the 120V side. You can get metal shallow old work boxes for the dimmers. Standard metal boxes or whatever is needed for the transformers. Might be able to just use the BX and a strain relief if the transforms accept that type connection.

[MstrCarpenter]

They were much, much more expensive 5 years ago, but did you know you get a driver (transformer), 16' of color changing strip light, and a remote control for about $30? Free shipping and you can have it by Wednesday if you have Prime. They even have aluminum housing and diffuser kits for strip lights. Something else to consider; you may have a magnetic transformer floating around with the required voltage and amperage output (12 or 24 VDC, 1 amp or more) that can be used with a simple dimmer or you can purchase one for around $5. You do not have to use a special (i.e. expensive) "LED dimmer" with these. Even the $3 rotary dimmers will work but the slide dimmers in either toggle or Decora are more stylish and for $10 more you can get ones that you set your preference for the highest and lowest "brightness" behind the cover plate. I've found the simplest way to control strip lights is to switch half of a receptacle with one of these switches, plug in the transformer, and connect the lights with fire alarm wire ( it's rated to be buried in the wall/ceiling).