I want to do some (low voltage) uplighting in my yard and on my house. I have determined that the most efficient layout will require three branches of wiring:
One will be 140W, 45' long. 4 lights (35W each), all spaced almost evenly (first light about 10' from the box, the rest spread out to the end, 10-12' feet apart).
One will be 70W, 35' long. 2 lights (35W each), one about 10-15' out and the next at the end.
One will be 40W, 70' long. 2 lights (20W each) at the very end, almost next to each other (uplighting a tree).
This is a total of 250W, so I should be able to use a 300W transformer.
My questions are:
-What gauge wires should I use for each? It's okay to mix and match, isn't it? Also, while I know professionals typically use 12- and 10-gauge wire, I have a coil of 16 gauge wire from a previous project that I would like to re-use, could I get by with that on any of these runs?
-If I have a transformer that has two posts and a common, how should I connect the wires? Should I put the 70W and 40W wires (110W total) together on one screwpost and the 140W on the other?
I do not waste time running 16ga wire for lights, use the heavier gauge as you will get much less voltage drop (dc voltage is much more sensitive to resistance than ac), plus you will not have a problem if you decide to add more lights or extend the length of the runs in the future. For the same reason,do not waste your money on a transformer that is maxed out from the start, get a quality 600w unit and you will not regret it. It is best to try to keep the load balanced as you suggested.
I know there are going to be contrary opinions from others who will try to dazzle you with their numerical calculations about wire gauge and capacity, but for me lessons observed in the real world are better than theoretical numbers.
Last edited by troubleseeker; 01-15-2007 at 10:30 PM.