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3 LV Xformers along a drive question

Discussion in 'Landscape Lighting' started by cooper5114, Jun 23, 2008.

  1. cooper5114

    cooper5114 LawnSite Member
    Messages: 13

    I would like to get an opinion on the best way to run 120V wiring along a long driveway. I'd like to have 3 recepticles along the way -- one at 250', 500' and 750' (the drive is about 850' long) each one used to power a LV xformer.

    My thoughts are to run these in series and i'd allow 600W (5Amps) for each transfer. So the first run would need to carry 15A, the next 10A and the last 5A. If i just use a voltage drop calculator...it says i need to run #4 for the first 250' then #6 for the next and then #10.

    Does this seem reasonable? Also i cannot seem to find specs on transformers as to what an allowable input voltage range they will operate with?

    Any help is surely appreciated.
  2. JoeyD

    JoeyD LawnSite Silver Member
    Messages: 2,933

    You will need to consult with a liscensed electrician. I dont think any of the guys that participate here are liscensed EC's. The onkly thing I can say is that it will be the most expensive part of your lighting install running the 120v that far.

    I can tell you that mist LV 12v transformers operate on a 10-1 ration so if you have 120v incoming you have 12v at your 12v tap. 130v you have 13v at your 12v tap......you can do the math from there.

    Our units can operate with as little 60v incoming I believe, but anything less and you begin to put a strain on the unit and can cause an unwanted humming noise. You should try and provide as close to 120v as possible...and again i am speaking in regards to our units, I dont know how others would do.

    I will also throw out that we have a 24v system which would allow you to put the transformer closer to the home and just run LV cable down along the drive.

  3. cooper5114

    cooper5114 LawnSite Member
    Messages: 13

    i do plan on talking to an electrician but i would think that this is somewhat of a common scenario folks here encounter. How do the distances compare between 12V and 24V?
  4. David Gretzmier

    David Gretzmier LawnSite Gold Member
    Messages: 3,645

    A transformer with multiple taps up to 22, 24 volts allow you to go much further from the transformer than ones with only 12-14 volt taps. I'm not sure you can go 850 feet away from a trans even on a 24 volt tap, or how much load you can put on that wire. my charts for low voltage only go to 300 feet away. with very low loads, maybe just a few lights per wire run, it might be possible to stick to low voltage only. I asked an electrician many years ago before copper wire prices tripled to do outlets along a 1000 foot driveway as you described. The price was in the 2-3 thousand range. nowadays I would expect 5-7500- but it will make it way easier for low voltage to go in. it may very well be cheaper to do it as Joey descibed. good luck.
  5. Pro-Scapes

    Pro-Scapes LawnSite Platinum Member
    Messages: 4,180

    If you do irrigation and such and can pull the trench for him your cost will come way down if all they gotta do is lay the wire and hook it up. We just did one about 650 ft from the home. We had an open trench on site and I know it brought the cost down to less than half if the EC had to pull the trench.

    Its not about cost its about doing it right. Running the line voltage would be the most effecient way for your client. You could however do line voltage half way and use Uniques 24v system and depending on your loads be ok.
  6. JoeyD

    JoeyD LawnSite Silver Member
    Messages: 2,933

    With a 24v system I can go 850ft on 10/2, and power up 105w. This would require the 30v tap. I guarantee this would be cheaper and easier to do than pulling 120v......But that is up to you to decide if you want to run a 24v system......
  7. Pro-Scapes

    Pro-Scapes LawnSite Platinum Member
    Messages: 4,180

    I dont know Joey. He is talking about putting a 600w trans out there. The drive is 1000 ft long. Thats alot of runs of 8 or 10ga wire to get 600w capability in that far zone. 6 runs out to a 1000 ft area is 6k ft of 10ga wire That alone could cost over 3k and thats just for the one zone. This isnt even factoring in the low voltage lines to run the mid section or the upper section.

    You can pick up 1000 ft of 10/2 UF for under $1k... Rent the trencher if you dont have one for say 100 bucks... couple man hours have it all installed then have the EC come out for a couple of hours to hook it all up and still be under your LV wire cost not to mention to bury 6 10ga wires to just that far area your going to need to dig a pretty nice trench anyways.

    Make the job or break it. 1000 ft drive is not going to be cheap. I personally would do line voltage all the way out. Now if a deep trech is not possible you got a whole different ball game.
  8. NightScenes

    NightScenes LawnSite Silver Member
    Male, from Kingsland, Texas
    Messages: 2,209

    Why would you run the 120v circuit in series??? You should be installing a 20 amp circuit in parallel and the load that you will be placing on it will help determine the size of the wire that you will need.
  9. cooper5114

    cooper5114 LawnSite Member
    Messages: 13

    using a calculator that limits loss to 3% yields this

    250' carrying 5 Amps needs #10
    500' carrying 5 Amps needs #8
    750' carrying 5 Amps needs #6

    250' carrying 15 Amps needs #6
    250' carrying 10 Amps needs #8
    250' carrying 5 Amps needs #10

    so running this stuff serially and stepping it down is a good bit cheaper than running three seperate circuits.

    Though this is a long drive i really don't need a lot of lighting along it...maybe a total of 10-15 lights...if that helps on the approach.
  10. David Gretzmier

    David Gretzmier LawnSite Gold Member
    Messages: 3,645

    10-15 lights total? to light a 1000 foot long driveway? am I figuring this right, one light every 80-100 feet? or 10-15 lights for every 250 ft ?

    if you go with a 24 volt trans, 850ft of 10guage to run 105 watts, you'll need several runs of that, and that isn't gonna be cheap either, but cheaper overall than 120 volt option, as low voltage does not need to be buried as deep.

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