voltage drop w/ Landscape Lighting

Discussion in 'Landscape Architecture and Design' started by MowingisMaddness, Oct 18, 2004.

  1. MowingisMaddness

    MowingisMaddness LawnSite Senior Member
    Posts: 260

    Hey everyone, I am designing my first landscape lighting project and need some help.

    The customer has about 90' of sidewalk to light. I am currently dealing with a lighting company that sells Kitchler. They haven't been very helpful answering my questions. I would like to lay out the lights on both sides of the sidewalk about 8 feet apart. I thinks six foot spacing would be better but the customer is trying to hold the price down.

    I am planning on installing 12 fixtures (18.5 volts each) and a 300 watt transformer...

    Questions:

    1) Could someone explain the voltage drop factor? I will be running 90 ft of wire on one side of the walk and then 90 ft on the other side. Is this possible or will the voltage drop be too much?

    2) I would prefer to use only one source because the site previously had lighting running on 110 volts and I plan to use the old power source. Plus this is the only existing power source currently available... Will this work or am I going to be forced to install an additional power source?

    3) Obstacles??? I will have to go under the sidewalk twice(pavers) and am planning on digging down and driving a 1' cast pipe under the walk with a sledge hammer... I have read a few posts on this and don't understand the water hose concept. Plus I would be worried about the paver base being damaged with the hose method...

    4) I will also have to go under a flagstone planter... same method as going under the sidewalk I guess???

    5) What is the average spacing for path lighting? Could path lights be spaced 10' to 12' apart??? I know it could be done but would it look bad?

    I could really use some feedback on these issues... no one around me seems knowledgeable on the subject...

    Thanks, aj
     
  2. MowingisMaddness

    MowingisMaddness LawnSite Senior Member
    Posts: 260

    http://www.weberelectricsupply.com/gde.html

    According to the formula on this website I will have a 22% Voltage drop at the end of a 90 ft run...

    0.0011 x Total Watts on Cable x Length of Cable = Voltage Drop in %

    My application (.0011x222x90) 21.9%

    However, that is if all fixtures are on one cable... Will I be able to run two cables into the transformer?? If so it would result in only a 11% voltage drop...

    Website says "Halogen lamps' light output and life are severely affected by more than 10% voltage drop"

    So I am close to that... and if I use heavier gauge wire I should be able to get under the 10% line... :cool: :cool: :cool: Is this correct??? ;)

    :help: :help: Does anyone know the factor for calculating voltage drop for 10 or 8 gauge wire.... (ie for 12 gauge this site says its 0.0011) :help: :help:

    12 Gauge [[0.0011]] x Total Watts on Cable x Length of Cable = Voltage Drop

    So the factor for 12 Gauge is .0011

    10 Gauge [[0.?????]]
    8 Gauge [[0.??????]]
     
  3. T Edwards

    T Edwards LawnSite Member
    Posts: 230

    I think your best option is to install (2) 300w transformers, located in the center of each 90' parallel run. If you're spacing them 8' apart, driving 24 units is asking an awful lot from one transformer. I guarantee there will be some overheating somewhere, and the weak link in the chain will fry and open the circuit and good luck finding it then.

    Best of luck
     
  4. MowingisMaddness

    MowingisMaddness LawnSite Senior Member
    Posts: 260

    T Edwards,

    Thanks for the feedback :) However, there is only a total of 12 fixtures... 6 per parallel run. So that cuts the load to half of what you were figuring... aj
     
  5. activelandscaping

    activelandscaping LawnSite Member
    Posts: 241

    I only use Vista lighting. I would go with a 400W ( 300W if it turns out your bulbs are 10W )transformer and run 2 legs @ 6 lamps/leg. Pound under the walkway with a piece of 3/4" copper and use funny pipe as a sleeve for your wire.

    Are you sure that these aren't 10w bulbs and the fixture is merely rated to 18.5 V? I haven't heard of a 18.5 V bulb before.
    Use 10/2 wire max. Using 8/2 is overkill and it's like working with steel cable.

    Regards,
    Active
     
  6. T Edwards

    T Edwards LawnSite Member
    Posts: 230

    You stated : The customer has about 90' of sidewalk to light. I would like to lay out the lights on both sides of the sidewalk about 8 feet apart.

    That works out to be 24 lights.....??
     
  7. activelandscaping

    activelandscaping LawnSite Member
    Posts: 241

    I was guessing a staggered pattern @ 8' distance between alternating lamps. 24 lamps in a 90' run, don't forget to wear your sunscreen. :p

    One more thing, always build extra wattage into the job. That way you don't have to hand the customer a estimate that includes another transformer if they want to up-light a tree or add another path light.:)

    Regards,
    Active
     
  8. PrecisionOutdoor

    PrecisionOutdoor LawnSite Member
    Posts: 24

    I believe he meant 18 watt fixtures. I am with active on the 400W transformer and atleast 2 legs. The voltage drop numbers you were looking for are below.

    #18 .006385
    #16 .004016
    #14 .002525
    #12 .001620
    #10 .001080
    #8 .000640
    #6 .000395
    #4 .000249

    Precision.
     
  9. MowingisMaddness

    MowingisMaddness LawnSite Senior Member
    Posts: 260

    T Edwards,

    To have 24 fixtures in 90 would be 4(3.75 actually) foot spacing not 8??? There is just one sidewalk 90 feet long. I am planning on running a loop on each side with 8 feet spacing... like

    x-----x------x-----x-----x-----x
    [][][][][][[][][][][][][][][][][][][][][][][]
    ---x-----x------x-----x-----x-----x

    Sorry I didn't communicate it better... so yes staggered 8 foot spacing...


    Active, Yes I meant 18 watt, 10 volt :dizzy:

    I agree with the 300W Transformer, but two things

    1) More lights more voltage drop problems
    2) At customers limit for budget now ;)

    And why only Vista...

    Active and PrecisionOutdoor,

    Do you agree with the 10% max voltage drop for halogen bulbs???


    PrecisionOutdoor,

    Your voltage drop factors hurt my situation... The website
    http://www.weberelectricsupply.com/gde.html

    Has the 12 gauge factor at .0011 your number is .001620
    which changes the drop form 12.9% to 16.2% ;) That's not good...even if I use 10 gauge your number is .001080 for 10.8 ;)

    Where did you get those numbers??? Do different manufactors have different factors????
     
  10. MowingisMaddness

    MowingisMaddness LawnSite Senior Member
    Posts: 260

    http://www.vistapro.com/wirewizard.htm

    for figuring voltage drop, but it calls it volt tap???

    my numbers zone 1 111W, 90 ft zone 2 111W, 90 ft

    The Wizard says: use 12 gauge wire, drop of 12%???
     

Share This Page