Voltage Drop Equation For Landscape Lighting
Use this voltage drop equation to figure out how many volts your wire will lose over a distance:
Total watts on low voltage wire * length of wire run in feet / wire size constant listed in chart below = VOLTAGE DROP
WATTS * WIRE RUN LENGTH / CONSTANT = VOLTAGE DROP
| WIRE SIZE | CONSTANT |
| #16/2 | 2200 |
| #12/2 | 7490 |
| #10/2 | 11920 |
| #8/2 | 18960 |
(note: the smaller the number the bigger the wire. 8/2 low voltage wire is the largest size)
Example:
100 watts of lights at the end of a 200ft wire run on a 10/2 wire
100 * 200 = 20,000 / 11,920 = 1.68 volts
So if you have 12 volts coming out of the transformer the voltage drop equation tells us the voltage will be reduced by 1.68 volts to 10.32 volts.
10.32 volts will produce a slightly yellowish light.
We recommend using a multi-tap transformer so you can increase the voltage to get each landscape light above 10.8 volts.
Increase voltage on far wire runs with our multi-tap transformers.
Click Here to —-> Learn More About Voltage Drop.
Southwire Voltage Drop Calculator —-> Southwire has a great voltage drop equation calculator and even a mobile app for iPad, iPhone & Android devices. We do not stock Southwire low voltage cable we stock and sell Colman Cable low voltage wire. If you are interested in Southwire products we can order them.
Cast Lighting Voltage drop Calculator —-> Cast lighting provides the most in depth tools for landscape lighting professionals. We sell Cast Lighting but the products are not loaded on our website. If you are interested in any of their landscape lighting products please contact us for a quote.
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whats the constant for 14/2?
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I think this will be influenced by the wall thickness of the cable won’t it? What wall thickness were you using. I looked up Southwire 10/2 55272 30V cable is 30 mil and 10/2 552135 150V cable is 45 mil.
Can I mitigate the voltage drop by using a bigger transformer ( higher wattage)? I am currently using a 200 W transformer and the wiring that I laid out has caused a significant voltage drop. I like to know if instead of rewiring, I can buy a bigger transformer?
Thanks for your advice, in advance.
in your voltage calculation equation, is that equation based on a series run? or, for a T
connection? I also have a run about 300 ft.
thx mike
How can i do a 250ft run?
I am only using 10ea. 3 watt led fixtures on the run. So total of 80 watts. The fixtures are evenly spaced over the 250 feet of straight driveway.
I already have a 12volt 300 watt transformer but im not sure it will work over the long distance.
I will run 12-2 cable.
Any suggestions??
Help is greatly appreciated!!
Good information concerning voltage drops referencing a light-scape installation project. Probably spend the extra money upfront and install 10/2 cable as this is the majority of labor involved. If you install a smaller size, might be concern of too much voltage drop that can be overcome by a larger transformer tap output.
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Thank you