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I am finishing my basement and would like to do 2 sets of LED strip lights. One will go in a small 4x8 room under my stairs, another a large theater room 13' x 15'. I am a beginner when it comes to electrical wiring, but usually not afraid to tackle something and learn something new.

I have been reading a lot online trying to figure out how to put this together and wanted to run my thoughts by the exchange and see if i'm on track, and ask for a few recommendations.

I'm looking at using some lights like this:

enter image description here

From my research, If I want to wire directly from my circuit breaker box, I need to buy one of these, but I'm not sure how many watt to buy? My plan is to just stick this in my utility room right by my circuit box.

Non Waterproof 100 Watt, Led Driver Power Supply

enter image description here

Here is a rough sketch of what I think I'm going to do. I just want someone to tell me if this is right?

Just to outline my questions:

  1. What watt power transformer should I be using?
  2. Can I run 14 gauge wire directly from a circuit 15 amp breaker to the transformer?
  3. Can I plug in all 5 circuits of LED strips on top of each other to the output of the transformer?
  4. Is this the recommended way of doing what I'm trying to accomplish?
  5. I would also like to add a on/off switch, do they make a wall switch for 12v?
  6. Can low volt wires come right out of the wall, or do they need a junction box before being connected to the LED strip lights?

*New Question 7. After some additional reading last night I saw that the cheap LED strips on Amazon can get very hot? I plan to light a children's room under my stairs with a very low ceiling. I also read that more expensive lights should not get as hot? My main reason for choosing LED lights was for low heat in a confined area. Dose anyone have any experience with the heat output of these lights?

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What gauge of wire are you planning to use between the transformer to the LED strips? –  Nathan L Jun 5 at 20:15
    
I guess that's another question, I saw one diagram that used 16 gauge for short runs and 18 gauge for longer runs, I believe this was to try to avoid voltage drop when the lights were further away? –  TravisK Jun 5 at 20:56
    
@TravisK I'm sure you have that backwards...16 gauge is thicker than 18, and you want thicker wire for longer runs to minimize voltage drop. –  Grant Jun 5 at 21:20
    
If you're working in an area covered by National Electrical Code, see article 411. –  Tester101 Jun 6 at 10:22
    
I will also strongly suggest you switch the 120V line ahead of the transformer. If you insist on switching certain areas separately you should get separate transformers/drivers. They are extremely cheap these days. I like these: amazon.com/Ledwholesalers-Power-Suppply-Driver-Transformer/dp/… They come in 30, 60 & 150 watt sizes, and are self contained unlike the one show in your original post. –  Speedy Petey Jun 6 at 10:53

2 Answers 2

What watt power transformer should I be using?

You can use a power supply like the one pictured, rated for the amount of LED's you will be driving. Read the specs on the lighting. They should tell you how many watts per a given length of the strip. So if it says, for example, that needs about 1 watt per meter, then a 15-foot section would require a 5 watt power supply. Take your total length of 76 feet, and divide by the strip's requirements. It wouldn't surprise me if you ended up somewhere in the ballpark of 20 to 30 watts.


Can I run 14 gauge wire directly from a circuit 15 amp breaker to the transformer?

No. You can't put the power supply inside the wall, and you can't bring the wire out of the wall without going through a junction box. The best way to do this is to put a cord on that power supply, and plug it into an existing outlet. There is no need whatsoever to add a new circuit or connect these directly to a circuit breaker.


Can I plug in all 5 circuits of LED strips on top of each other to the output of the transformer?

Yes, you can wire multiple strings in parallel at the power supply. If the sections are short, you can also wire them end-to-end. Double-check the specs for maximum length of a single run.


Is this the recommended way of doing what I'm trying to accomplish?

The recommended way is to plug into an existing outlet. If your lighting requirements added up to 1000 watts, you'd want a new circuit. At 20, 30 or 50 watts, it is ridiculously small in household circuit requirements.


I would also like to add a on/off switch, do they make a wall switch for 12v?

Any switch can be used for 12v. I would put the switch before the power supply. Put a cord on the power supply like this cord with switch.


Can low volt wires come right out of the wall, or do they need a junction box before being connected to the LED strip lights?

The low voltage wires don't need a junction box, but they do need a junction plate, like those used for phone jacks.

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This answer is good and I'd suggest two things additionally: Use a separate transformer for each room (you can use a smaller transformer for the shorter strip, obviously), and plug the transformers into 120V outlets switched by regular wall switches in each respective room. The 120V wiring for the switches and outlets is absolutely standard stuff. The benefit of this is that the transformers are only on when the lights are on, instead of 24/7 (they still draw power, even with no load). –  gregmac Jun 5 at 22:17
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I've edited the formatting of your answer, so that a reader doesn't have to flip back and forth between the answer and the question (which is especially annoying on the mobile app). Feel free to revert the edit, if you like. –  Tester101 Jun 6 at 10:07
    
Thanks this is a great answer. For clarification, I want to place the transformer in my utility room, and run the low voltage to my LED Strips. These runs will be anywhere from 5 to 30 feet away from the utility room. From your answer, it sound like I might be best off adding a couple switched outlets in my utility room that have an on off switch in the room that I plan to use the lights. This will allow me to turn off power to the transformer when the lights are not in use? Then I can just run my 16 or 18 gauge wire out to my led strips from there. –  TravisK Jun 6 at 13:55
    
Yes, you can do that. Although it still seems to me a little convoluted to put a switch in the theater room, to control an outlet in the utility room, to drive low-voltage wiring back out to the theater room. Put the switched outlet right in the room and use a small 70w power suply or the ones Speedy Petey linked to. It will blend right in with the theater equipment. –  Grunthos Jun 6 at 15:58
    
To add to the suggestions here, put the transformer and all hidden (plugged into an outlet) like under the stairs or closet, then use an RF remote (does not require line of sight) like this one I've had good luck with: amazon.com/gp/product/B00AHU2U7O –  mikegreen Jun 10 at 20:05

After looking at the NEC code book, you need to limit it to 5 amps, but with 16 gauge wire at 5 amps you would have a voltage drop of 2V after 50 feet (I making an assumption about what you mean when you say longer run).

You probably want also want to fuse each line from the transformer individually, because if it shorts it will pull 8 amps from the 100w transformer if not otherwise limited. If I was going to rig something like that up at my house, I'd probably use an automotive fuse bus and use 2A fuses for each (24w) strip.

If installing a switch, I'd probably switch the entire transformer running 120 to the switch like other lighting and placing the transformer and fuses in a closet close to the strips to reduce voltage drop.

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What does your local code book say that would limit the wiring to 1-2 amperes? –  Tester101 Jun 6 at 10:10
    
I am also curious as to what your code books says on this. Please provide a code citation. –  Speedy Petey Jun 6 at 10:49
    
NEC specifies 5A for 0-20V, my local code book specifies a lower limit for systems not installed by a licensed electrician. –  Nathan L Jun 6 at 15:17
    
Edited to reflect my reasoning. –  Nathan L Jun 6 at 15:29

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