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03072013, 07:40 PM  #1 
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Voltage Drop
Hello all. I am new to this forum but am very active in several forums. I'm a big believer in them and have saved a lot of time and money using them therefore I am reaching out to the experts here on this one.
Before I posted this, I conducted a search on this forum to be sure I do not repost something that has already been answered. There were a few bits and pieces I was bale to string together but hope that I can get further help by explaining exactly what I am doing. I am about to instal low voltage lighting around my driveway. To paint a picture of the layout, imagine a Ushaped driveway with the two entrances running perpendicular to the street. At the opposite end is my house and deck. I plan on running 12 gauge wire from the transformer on my deck in TWO SEPARATE runs, run A and run B. Run A will total 192 feet with the first light at about the 40 foot mark. I will be putting a total of 6 spreader lights that are each 10 watts and one spot that will be 50 watts. Run B will also begin at the transformer on the deck and will be a total of 228 feet of 12 gauge wire. The first light will be at approximately the 55 foot mark. Again, on this run I will be using 6 spreader lights at at 10w a piece and one spot at 50w. I have calculated run A to have an approximate 1.53 volt drop. Run B will have a 1.82 volt drop. My question is whether or not there will be sufficient power to all the lights on each run assuming that I utilize a multi tap transformer and use the 14 volt hookup for run A and a 16 (or the next higher) for run B. My main concern is that run B is such a long run, that even if I compensate for the voltage drop by using the higher hookup, there will still be a difference in the brightness of the two strings of lights. Any advice or suggestions would be greatly appreciated. Thank you 
03072013, 07:53 PM  #2  
E2 Electrician
Join Date: Apr 2012
Location: Litchfield, CT
Posts: 4,893

Voltage DropQuote:
Last edited by stickboy1375; 03072013 at 07:55 PM. 

03072013, 07:58 PM  #3 
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Join Date: Mar 2013
Posts: 5

Voltage Drop
Thanks!
So if I combine the two runs into one run with all 12 T3 lamps (120 watts) on it, it will not affect the brightness due to voltage drop? That would be 120 volts on 351 feet of wire. I calculate a 5.6 volt drop on that long of a run. 
03072013, 08:01 PM  #4 
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Voltage Drop
Stickboy,
My fault, I misread. Four runs, not tow. Got it! Makes sense! 
03072013, 08:22 PM  #5 
E2 Electrician
Join Date: Apr 2012
Location: Litchfield, CT
Posts: 4,893

Voltage Drop
Yep... I think you will be okay with this scenario...

03072013, 10:13 PM  #6 
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Join Date: Jan 2013
Posts: 570

Voltage Drop
Are all the lights at the end, or are they spread out along the run?
If you run 14v, the first couple lights won't last very long. 
03082013, 12:07 AM  #7  
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Voltage DropQuote:
Run A will total 192 feet with the first light at about the 40 foot mark. I will be putting a total of 6 spreader lights spaced along the next 140 or so feet of this run. Run B will also begin at the transformer on the deck and will be a total of 228 feet of 12 gauge wire. The first light will be at approximately the 120 foot mark. Again, on this run I will be using 6 spreader lights spaced along the remaining 100 or so feet. Does that answer your question? I understand that I will need to account for voltage drop, but how can I do so without running too much current to the first few lights? The problem is the placement of the power source. Without tunneling under the driveway (which would be perfect but not on my wallet) I have to begin the run at the nearest power source which is approx 40 feet or so from the first light. Then run the remaining LONG wire on each run. Make sense? Thanks for all the input! It is really going to help. 

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