Were installing cabinet lighting in our kitchen and no one seems to know for sure what gauge wire to use -- not even our electrician!
We have 18 x 20watt xenon puck lights across the top cabinets of the kitchen and a 12v 600w transformer ( 2 x 300 watt legs). Were planning on splitting the load between the two runs. The wire distance from the transformer to the last light is about 30 feet. So one run will be 15 feet and power 11 lights. The other will be almost 30 feet and power 7 lights. What is the proper wire gauge to use??? So confused
Distance matter too... The longer the run the heavier the wire needs to be. Also, it is important to you the correct wire coming off the transformer if requires wire that can take the heat build. Check with the manufacture of the transformer you are using for the best information.
When you're done, check the voltage that the 'former is putting out is less than or equal to 12, otherwise your lamp life will be shortened.
If you use less than 600w worth of lamps the voltage will definitely be above 12v.
The last light in a string [which is only using 20/12 = 1.7A] will get lower voltage but I don't know how much lower you can go and not get a perceptibly dimmer bulb. A 5% voltage decrease gives a 16% brightness decrease.
At the other extreme, each bulb could have its own wire pair that only carries 1.7A and the 'former would have 18 skinny wires on each of two binding posts. If you make them skinny enough the voltage to each lamp will be slightly below 12v and the wires still may not get so hot that the NEC gets upset.
I'd lay out the whole thing first and check that everything works OK.
18 ea. 12v lights totals to 216v so you can't put them in series and power them with 120v.
If you had 20 you could put 10 ea. in series, and then parallel that with the other 10, put 120v into the assembly of two strings and then use reasonably sized wire that only carries 3.4A.
Of course, if one burns out you have the same problem that some Christmas lights get.
These extremely bright lights have UV warnings, so I dimmed mine by running them at substantially below rated voltage.
What would be the correct 12awg wire to use then? It should be stranded preferably right? Also the only place it would be in a wall is in the attic for about 2 feet. The rest is just over the cabinetry.
Do Xenon lights get hot like halogens? I installed halogen puck lights under my kitchen cabinet - a lot of heat came through into the cabinet and I was concerned of the finish being damaged. You could not hold your hand on the floor of the cabinet... I installed a piece of sheet metal heat shield between the light and cabinet as a mitigation (4"x6" precut, availabe at big box stores where the roof flashing materials are located).
If I had a do-over I would have used LED puck lights.
xenons run cooler than halogen, but still fairly hot. I still don't get what the proper wire to use is then -- if landscape wire isn't correct... what's a good wire for this?
If it's 12v and you put an inline fuse or fuses at the upstream end of the wire, I'd think you could safely use almost any wire that doesn't get above 60C or so due to the current flow through it, but I'm sure the NEC has some other things to say about this.
We're not building a Space Shuttle here.:whistling2:
Post a link to your candidate 'former.
Some may have an internal fuse or breaker, some may be short circuit proof, like a bell 'former.
I guess I'd use #14 or #12 and arrange the wiring such that the current in each wire stays under 15A or 20A or so, and the voltage supplied to adjacent lamps is close enough to being equal that most people cannot see a difference in brightness.
Romex is good to 600v but if you can find a wire whose insulation is good for 25vac or so and is approved for this use, etc., etc., that should be good enough.
If your lamp life is unsatisfactory you
could use a $3 voltage dropping resistor or inductor upstream or downstream of the 'former and probably be NEC-non-compliant
or else find some kind of dimmer that will work at 12vac or else can be used upstream of a 'former.
Don't try to cobble together some system that still would not be rated for in wall use. If NM is acceptable in your area you would use that in the wall.
We have 18 x 20watt xenon puck lights across the top cabinets of the kitchen
So one run will be 15 feet and power 11 lights. The other will be almost 30 feet and power 7 lights.
If you use #10 AWG the voltage at the last bulb of the first string will be 11.89v, and at the second string, 11.95v.
These brightness differences will probably not be noticeable. The current at the beginning of the first string is 11.7A and 18.3A for the second.
My spreadsheet is still set up to solve this type of problem for more or less equally spaced lights so if you have other configs you'd like to try I can tell you what to expect.
I guess a 5% voltage drop from one end of the string to the other will not be noticeable.
On a current draw basis alone you could use one long piece of #10, 2 ea. pieces of #12 or 3 ea. pieces of #14, depending on how many lights are in each string.
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