12vdc outdoor wiring

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navychop

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My wife and I are almost finished building a 24' long pergola with interior pathway, next to the deck in our back yard. I look forward to regaining full use of my hands and arms one day, but that's another story.

She now wants to run small sconce lights inside it so that people can see their way at night. Plan A was to hang small solar lights there. No acceptable lights have been found. Plan B is to run 120v lights on a dimmer. Neither of us is fond of this idea. Plan C is to run 12vdc lights.

To implement C, we need outdoor fixtures, relatively small, preferably LED or CFL, of a nautical theme or old timey shade lights. Can't find these in 12v (looked thru literally hundreds of candidates). But we can find 120vac fixtures that meet the bill, and there are medium base 12vdc bulbs available.

I can plug a transformer into an existing outdoor outlet, or hard wire it. Then run the wire up one pole, across the top and down the four poles she wants lit. I note that the wire sold for this purpose is 10 or 12 gauge, certainly enough to carry 120vac. Isn't that unwise overkill, as it might encourage someone in the future to convert it to 120, when it might otherwise not be so suited (not UF or outdoor use romex, at any rate)?

Do I have to use regular (large, unsightly) mounting boxes for the fixtures?

BTW, we will be growing grape vines and kiwi on the pergola.

Any suggestions or comments?
 
You need the heavier gauge at 12vdc to accommodate the higher current those low-voltage applications require, and over those distances. A 4 watt bulb draws .33 amp, higher wattages proportionately more. You can see how that could add-up when you get to 20 or 30 bulbs on a circuit. That kind of wire is not "overkill" and tho' it might be "unwise", it's suitable/approved for the purpose. If you're planning fewer bulbs, then lighter gauge wire might work out fine. But those low-voltage wires are intended to be buried. I'm not sure how well they'd hold up exposed to UV, etc...

I can't completely envision your application, but I think if I were doing it I'd use a 120-volt circuit through UF or perhaps even plastic conduit. I've got both types in use at my place, and the low-voltage stuff where I need the low-level lighting in the flower beds along the front of the house. I like the strength, resilience, and flexibility of the systems I've wired in conduit the best. In your case it would also provide best protection from those meandering vines...!
 
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