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I'm installing under cabinet lighting and haven't worked with low voltage wire before and trying to determine the best option. I'm using 18 gauge wire (stranded) to wire LED lights. In my particular situation, I have my wires coming from the power supply under one of the middle cabinets. I have about 4 more feet on the right side than on the left, so to protect against potential voltage drop, I want to run the wire from the power supply straight up, and then from that wire, connect to two separate runs (one for the left side and one for the right). My question is how to best connect the wires. I was initially thinking of using wire nuts to connect them - for example, the two positive wires on each run tied in with the positive wire from the power supply...so 3 positive wires wire nutted together. Same with the negative wires. I then read something where I'm now a little concerned in using wire nuts for stranded wire. If I do end up going that route, I'll also wrap electric tape around the nuts to help prevent any possible movement. And yes, I have nuts for the proper gauge, but I think those are always rated for solid and not stranded, but I could be wrong.

The other consideration I had was heat-shrink butt splices, but it would basically be 1 wire in one side and two wires in the other. This may be problematic because the best size I can find is 16-14 gauge. That would work I think for the side with the two 18 gauge wires going in, but maybe not for the side with just one 18 gauge wire.

Hopefully this makes sense. Any suggestions on this?

Thanks!

Chris

  • Generally LED under counter lights come with kits and accessories that come with a variety of splitters and splicers etc. Could you go online and see if the supplier of the kit has anything like that? In general I don't like to see anything just spliced in open air, and definitely not in wire nuts. – Retired Master Electrician May 15 '17 at 18:31
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    Wire nuts are fine with stranded wire, The same rules apply in a box and correct size for the wire gauge. – Ed Beal May 15 '17 at 18:42
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    Yeah, I use wire nuts all the time, they don't care solid vs stranded. They feel a little different solid vs stranded, and you have to square them off well if mixing solid and stranded, but they work fine. The blue is ideal for 3 #18s. – Harper May 15 '17 at 19:12
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    @Kris - Yes, that's what I have. – ctjoumas May 16 '17 at 18:53
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    @Kris Good to know! I did a bit of research before I settled on it so glad to hear. The diver isn't super large (assuming the one I have, which is dimmable, is still about the same as the others armacost makes). I have most everything hooked up at this point but waiting on some smart boxes to come in for the switch so I can connect the 120v romex line to my dimmer then temporarily install one tape light to make sure it all works before I finish the tape light installation. Thanks again for the help. – ctjoumas May 16 '17 at 19:45
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I use stranded wire for everything and I work in voltages up to 480. Wire nuts are my main splicing technique. Never had a problem nor had any reason to think I might. For 3#18 blue wire nuts are ideal.

If you are worried about voltage drop, up your wire size. Due to the strange economics of mass produced wire, #14 is barely any more expensive than #18. For going to individual strips I use #20 or #22 because I want delicate wires that are flexible so I don't put too much strain on the strip proper. But I splice up to heavier stuff within a foot or two.

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Your voltage drop with DC voltage and that additional 4 feet of wire you are stressing and jumping through hoops for will be VERY negligible [ .026 ohms of difference ]. Don't waste your time jumping unless you really need the exercise.

I am guessing that Power supply is Constant Current [for use with LED's ] at a set voltage so it will regulate properly for the two lights.

Now if you really want to exercise and spend more money and time : they make two wire to one wire splices , you could solder them together and heat shrink , or you can use the screw type connectors that allow you to join multiple wires.

  • He's worried about the current paths in the LED strip, which are smaller than 18 AWG and voltage drop can be a factor with 10 feet or more. – Harper May 15 '17 at 19:10
  • Right - I'm not worrying about voltage drop... I'm splitting to help with it even though I agree, it'll be negligible. However, I must split like this because I'm feeding it to the left and right of a hood vent, so I need two separate runs. Technically, I could just route it all the way to the left, then go all the way to the right and go behind the wall for the part under the hood, but that is a bit overkill. The longest run will be < 8 feet (can't remember exact), so not a problem with length. – ctjoumas May 15 '17 at 19:21
  • @user1587736 yes your splitting is not an issue - parallel runs, the length of your runs is very short. I would just run them directly from the power supply - if you do not desire that - buy a two wire terminal tab. connect to power supply and run wires equally from terminal tab to lights - search for 3 Pin Compact Wire terminal. Either way you will be fine. – Ken May 15 '17 at 19:39
  • @Ken - When you say you would run them directly from the power supply, do you mean connecting two separate wires (so two positives in the one slot for positive on the power supply and two negatives in the one slot for negative on the power supply)? That's initially what I was thinking but didn't think two separate wires could be run to the power supply. Otherwise, if I find a two wire terminal tab, would you install that next to the power supply so it's accessible or would it be fine to close that up in the wall? If If ever needed to get back there, I could from the other side of the wall. – ctjoumas May 15 '17 at 19:56
  • @ctjoumas yes connecting them at the PS as you stated. Either place you put the terminal connector is fine - getting to it easily in case you were to pull on it accidentally might make it better for you. I tend to try to cover the workings of things so no one really knows it is there unless they had a reason to know. – Ken May 16 '17 at 22:38
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Not sure how to give credit to Ken's answer, which is the route I went based on his comment.

I wasn't worried about voltage drop - the runs in my circuit were very short and I split it in the middle to avoid any concern (and even if I had just done one string for the entire side, it would have still been fine). So, the suggestion to go ahead and connect the two separate runs to the power supply is what I went with and it worked just fine. This way I didn't have to worry about putting any type of junction box behind hte wall where I couldn't get to it behind the backsplash - if I ever need to adjust anything, I have easy access to it at the power supply underneath of the cabinet.

Thanks, Chris

  • You can give credit to an answer by voting it up - click the up arrow next to the answer. As you are the asker of the original question, you can also mark it as the accepted answer - if the solution provided worked for you - by clicking the check mark next to the answer. – mmathis Jun 19 '17 at 13:21
  • Yea, I would be able to do that but it's not an "answer", it's a comment - I don't want to give credit to an answer that isn't what I went with (Ken's initial answer, below, is about voltage drop which wasn't my issue; he followed up with a comment on that answer which is what resolved it for me. I can vote up his answer to give him credit, or if that's the only way to give credit to a comment within that, but want to make sure I'm not screwing something up by going that route. – ctjoumas Jun 20 '17 at 13:45

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