low voltage lights

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charlie06

Member
Location
New York
A buddy of mine wants me to install low voltage lighting for his driveway. I took all the measurements. Using a 600 watt power pack fed with an existing 120v 20a gfi outlet. The P.P. has 2 low voltage ckts. 300 watts each. From the p.p. to the first cluster of 5 lights is roughly 145 feet away.
From the p.p. to the second cluster of 5 lights is 255 feet away. I used this formula for voltage drop.

cable length X total watts divided by cable constant X 1.5

-using 10awg as my feed from the p.p. to the lights then splicing to 12awg. for the lights.

I believe there will be too much of a voltage drop for the 50watt (250 watts per l.v. circuit) halogens to work properly.

I just want to make sure I'm correct before I convince him to run a H.R. from the panel to a central location down his driveway in pvc and incur extra cost if he doesn't have to. I hope what I wrote makes sense.

Thanks in advance
Charlie
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
Charlie, I would buy a whole bunch of the #10, and use one length for the closer home run, and two lengths for the farther home run, using one cable for each conductor.

By the way, you need to use amps for voltage drop, not watts. A 50w 12v bulb uses about 4 amps, so your load is just above 20a per section. Double the run lengths.

Your 145' run is 290' of wire, and the 255' run is 310' of wire. Once you know the voltage drop, then use the circuit voltage to determine what the drop percentage is.
 

dmagyar

Senior Member
Location
Rocklin, Ca.
Check for higher voltage taps in LV transformer

Check for higher voltage taps in LV transformer

Charlie, check the transformer to see if they have higher voltage taps in the transformer. Sometimes with a long run you can lessen the problem of voltage drop with the combination of larger wire and a higher voltage to start with. On the loads, try to connect not in a "daisy" chain, but in an array (rays in a circle) where you're not carrying extra loads through to the next fixture. You probably will need at least #6 to the hub in order to make the first group work, by my rough calcs. With those size wires, your hub splicing will also need attention.

Sorry, I just saw the 245' distance for the second group, thats going to be very hard to do without relocating a LV transformer closer.
 
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jwjrw

Senior Member
Where I buy my low voltage lights they have a voltage drop guide that would help you but I cant find it. Its a slide chart you match your distance and it give you what you need. I think it was by Vista Lighting. I know you can do the math but I think they mentioned longest distance for a run from transformer reccomended.
 

charlie06

Member
Location
New York
Thanks for the info. guys. I see where I made my initial mistake with my calculations, and the low voltage transformer I plan to use is made by Malibulights.com and they don't offer any other taps. I believe I will be running Home runs for these lights and place my power pack out in the field instead of on the side of the house.

Charlie
 
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