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Old 09-22-2009, 11:45 AM   #1
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12 volt kitchen cabinet lighting wire gauge? Help! :/


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

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Old 09-22-2009, 12:03 PM   #2
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12 volt kitchen cabinet lighting wire gauge? Help! :/


well im not an electrician, but what i have learned for my situation is that 10 gauge wire is good for 300 watts

i believe you still have to do the division for low voltage as you do line voltage.

10 gauge is good for 30 amps so 300/12=25 amps

so if this wrong i apologize in advance

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Old 09-22-2009, 12:13 PM   #3
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12 volt kitchen cabinet lighting wire gauge? Help! :/


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.

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Old 09-22-2009, 12:15 PM   #4
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12 volt kitchen cabinet lighting wire gauge? Help! :/


Calcs look good to me. I would agree. 300watts would need #10 wire.
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Old 09-22-2009, 01:19 PM   #5
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12 volt kitchen cabinet lighting wire gauge? Help! :/


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.

Last edited by Yoyizit; 09-22-2009 at 01:41 PM.
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Old 09-22-2009, 09:29 PM   #6
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12 volt kitchen cabinet lighting wire gauge? Help! :/


What do you guys think of running 5 lines of 12 gauge low voltage landscape wire for this? Ie. breaking up the load into 5 lines: 4,3,4,4,3 ?

1 12awg wire = 4 x 20 watt @ ~5 feet
1 12awg wire = 3 x 20 watt @ ~10 feet
1 12awg wire = 4 x 20 watt @ ~15 feet
1 12awg wire = 4 x 20 watt @ ~20 feet
1 12awg wire = 3 x 20 watt @ ~25 feet

And putting 3 wires directly on one leg of the transformer and 2 on the other.

Would that be acceptable?
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Old 09-22-2009, 09:31 PM   #7
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12 volt kitchen cabinet lighting wire gauge? Help! :/


And one more thing -- is it safe to jump about 2 feet of wire through the attic and back down (over where the range hood opening is) ?
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Old 09-22-2009, 10:24 PM   #8
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12 volt kitchen cabinet lighting wire gauge? Help! :/


Landscape wire is not rated to install in a wall, so you can't use that.
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Old 09-22-2009, 11:03 PM   #9
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12 volt kitchen cabinet lighting wire gauge? Help! :/


Quote:
Originally Posted by jbfan View Post
Landscape wire is not rated to install in a wall, so you can't use that.

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.
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Old 09-22-2009, 11:52 PM   #10
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12 volt kitchen cabinet lighting wire gauge? Help! :/


Quote:
Originally Posted by jbfan View Post
Landscape wire is not rated to install in a wall, so you can't use that.
It's a low voltage application, so is the wire type restricted, in wall? How about door bell, switch to garage door opener, etc.?
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Old 09-22-2009, 11:57 PM   #11
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12 volt kitchen cabinet lighting wire gauge? Help! :/


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.
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Old 09-23-2009, 11:00 PM   #12
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12 volt kitchen cabinet lighting wire gauge? Help! :/


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?
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Old 09-24-2009, 07:48 AM   #13
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12 volt kitchen cabinet lighting wire gauge? Help! :/


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.

Last edited by Yoyizit; 09-24-2009 at 07:52 AM.
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Old 09-24-2009, 08:18 AM   #14
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12 volt kitchen cabinet lighting wire gauge? Help! :/


What kind of fuse would you suggest? Does the transformer not provide this sort of protection normally?
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Old 09-24-2009, 08:31 AM   #15
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12 volt kitchen cabinet lighting wire gauge? Help! :/


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.

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