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03-07-2013, 08:40 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 re-post 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 U-shaped 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

03-07-2013, 08:53 PM   #2
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Quote:
 Originally Posted by vtl382 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 re-post 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 U-shaped 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
I generally run all my lights as home runs, all with the same length of cable... some of your lights are small wattage though... so IMO, i would run home runs to just the 50 watt loads, and just join the 10 watt loads together as in row (a) and (b) for a total of (4) home runs... This will allow you to adjust the voltage settings accordingly, and you should shoot for 11v at the fixture to maximize lamp premature failure and brightness.

Last edited by stickboy1375; 03-07-2013 at 08:55 PM.

 03-07-2013, 08:58 PM #3 Newbie   Join Date: Mar 2013 Posts: 5 Rewards Points: 10 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.
 03-07-2013, 09:01 PM #4 Newbie   Join Date: Mar 2013 Posts: 5 Rewards Points: 10 Stickboy, My fault, I misread. Four runs, not tow. Got it! Makes sense!
03-07-2013, 09:22 PM   #5
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Quote:
 Originally Posted by vtl382 Stickboy, My fault, I misread. Four runs, not tow. Got it! Makes sense!
Yep... I think you will be okay with this scenario...

 03-07-2013, 11:13 PM #6 Member   Join Date: Jan 2013 Posts: 814 Rewards Points: 948 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.
03-08-2013, 01:07 AM   #7
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Quote:
 Originally Posted by Toller 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.

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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