12v Landscape Lighting - single run 85' too long?

wynswrld98March 4, 2010

I have a half circle driveway 170' long with an outdoor covered electrical receptacle at the mid-way point. I'd like to place path lights along the driveway. So I'd put a 12v transformer plugged into the receptacle at the halfway point then run two leads out of the transformer, one heading each way towards the other end of the driveway entrance/exit.

I know running the wire in a circular pattern/other patterns is the best way to go and that straight run patterns are the worst due to voltage drops as you get to the ends farthest from the transformer but I wanted advice on my specific situation since straight line runs each direction away from the transformer are the only realistic way to wire this.

Is 85' too far for a straight wire run if I run 12 gauge wire?

If I put slightly higher wattage bulbs in the fixtures closest to the end of the runs (farthest away from the transformer) would that help get the brightness a little more consistent among the bulbs?

If you want specifics, the bulbs will be 12-watt T-5 wedge (not LED) amber, I can get same bulbs in 18-watt for possible use for farthest fixtures, transformer will be 300 watt. I'm not entertaining LED lights which are available in T-5 wedge due to lack of lumens, I'm actually trying to light a bit of the driveway and the brightest LED T-5 wedge bulbs I can find just aren't bright enough.

Thanks in advance!

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How many fixtures at 12 watts each?

    Bookmark   March 8, 2010 at 9:28PM
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16 total so 8 going one direction away from the transformer, 8 going the other direction away from the transformer

    Bookmark   March 8, 2010 at 11:51PM
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See the link for a voltage drop table. You can just double back the cable on each side. Running cable out in a circle doesn't mean it has to actually form a circle.

Here is a link that might be useful: voltage drop table

    Bookmark   March 10, 2010 at 10:23AM
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The voltage drop calculator may provide the answer, and putting the transformer in the middle and having the runs go out in both directions, as another member suggested, is a good idea. Another common thing to do is, using the 12 gauge wire, make parallel runs. So one run is 40 feet, let's say, and has 4 fixtures, and it's closest to the transformer. Then the second run has a 80' wire running along the first, and has 4 fixtures on the second half of the wire (between 40' and 80'). And so on with the others. One way to combat voltage drop is to use heavier gauge wire.

Also, spreading out fixtures puts more of a drag on the wire, so there's less drop-off when the fixtures are clustered.

    Bookmark   March 10, 2010 at 7:46PM
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