Wiring for LED

Discussion in 'Landscape Lighting' started by designer1, May 25, 2010.

  1. designer1

    designer1 LawnSite Member
    from midwest
    Messages: 15

    I am jumping into the LED market and have a few questions:

    what are the guidelines for wiring LEDS
    1. How many fixtures on a run
    2 what is the max amps per run
    3 what are the max watts per run
    4 how do I determine the above when it comes to LED
    5 what is the max distance of wire per run
    6 is 12/2 fine for most long runs with LED

    I know, lots of dumb questions, just want to be sure before I install my 65 light installation of LEDS.

  2. S&MLL

    S&MLL LawnSite Senior Member
    Messages: 751

    If you are asking these questions maybe you shouldnt be installing 65 "LEDS"

    Not trying to be an ass. But how do you bid a 20k dollar job and not know these answers?
  3. INTEGRA Bespoke Lighting

    INTEGRA Bespoke Lighting LawnSite Platinum Member
    Messages: 4,102

    The basic rules of wiring a Low Voltage Lighting system are the same whether you are using LED lamps/fixtures or incandescent lamps/fixtures. Voltage drop formula's do not change. Ohm's law does not change, The ampacity rating of wire does not change. You must know and understand these things to do any kind of LV lighting system installation. The only real difference is that you are using much more efficient light sources that will out live their incandescent counterparts. Do all the same planning and calculations that you would normally do. You will find you need lower capacity transformers and you will probably find you use the same amount of wire etc.

    I still use only 12 Gauge wire for my circuits. Given the volume of it sold it doesn't make much financial advantage to switch to a smaller gauge wire. This also provides the system a 'security blanket' in terms of circuit capacity if someone after you should choose to pop in an incandescent lamp here and there.
  4. designer1

    designer1 LawnSite Member
    from midwest
    Messages: 15

    Thanks for the constructive answer.

    I was under the impression that LED did not have to be wired with spider or hub methods. My rep is telling me that daisy chain is fine for led and not to worry about voltage drop.

    Is this correct or just sales BS
  5. emby

    emby LawnSite Senior Member
    from Ontario
    Messages: 380

    I think James answered it with very good accuracy. We do not wire in daisy chain. T-loop, hub, Lolipop are are well known designs but never daisy chain.
    Re-read James' post above as its dead on. Maybe your Salesman should read these threads and learn something. However you do it ensure that you maintain 10.8 - 12 volts at every fixture. Yes test everyone one of them.

  6. irrig8r

    irrig8r LawnSite Platinum Member
    Messages: 4,553

    Brings to mind a joke I once heard... which is too often accurate.

    Q: How can you tell if a salesman is lying?

    A: His lips are moving.

    And I will add my own tried and true observation: if he is wearing tassel loafers, don't believe a word.
  7. David Gretzmier

    David Gretzmier LawnSite Gold Member
    Messages: 3,646

    I too have heard the daisy chain thing is OK with LED. when I think of an LED boat dock job we talked about a year or so ago, I don't think it was possible to hub that. most folks seemed fine with daisy chaining LED's back then.

    I don't know much about you, so it is hard to give advice and know whether you will take it or not. So I hate to waste my time, but...

    But what I know is this- you have no experience with LED. If you had more than a little experience with low voltage lighting, you would understand about load and voltage drop, and would not ask the questions you asked. And while I applaud you are doing research, it is obvious you are in the middle of a bid or a job that you have no business doing. You are, no bones about it, doing expensive experimenting on a fairly large customers dime. You have no idea how to wire this. no idea how long the fixtures will last. I am also guessing you have no idea what lumens and what color temperature your fixtures are or should be, or even have the knowledge to ask those questions.

    if you want to jump into this business, do your own home first, then 3-5 friends and family homes for free. take a lighting class at a lighting distributor place and at least learn the basics of lighting . read some lighting books. work for a reputable lighting company as a hired hand and learn this trade.

    I doubt very seriously you will do any of the above, but it is my hope, for the professionalism of this business, and maybe your own guilt, that you at least do something other than listen to a sales rep and do some surfing before subjecting the public to pay for your work.

    we all started somewhere. But I cannot reccomend you starting with this size of a job, for pay, period.

    You can read my other posts and learn I am not a jerk. But in this case, the truth is what it is.
  8. steveparrott

    steveparrott LawnSite Bronze Member
    Messages: 1,276

    Many are claiming that it's OK to daisy chain LED fixtures for two reasons - low wattage per fixture and wide voltage specs for the LED's.

    First, consider the low wattage claim. LED's vary in wattage from 1.5 to 12 watts - meaning that a 10-fixture daisy chain is likely to consume from 15 to 120 watts. Using a likely distance of 20 ft to the first fixture and 100 ft. to the last fixture (with #12/2), voltage loss to the last fixture would be about 0.5V (with 1.5 W fixtures) or 3.0V (for 12W fixtures).

    In the worst case, the first fixture gets 12V while the last one gets 9V.

    This voltage difference would be OK if the second claim is true - that LED's accept a wide range of voltages - some do, some don't - check the specs. Even if a mfg claims a wide range of acceptable voltages, these claims must be viewed with scepticism. Extra voltage must go somewhere - heat, extra stress on the electronic components? - we just don't know. Also, will 9V produce the exact same brightness as 12V? Maybe.

    It's a little early to make assumptions. For now, I'd stick with wiring and testing methods that ensure equal voltage at the fixtures.

    By the way, I recently updated the CAST System Calculator to accommodate low wattage LED's: http://www.cast-lighting.com/support-installers/system-calculator-installers/.
  9. GreenLight

    GreenLight LawnSite Senior Member
    Messages: 527

    This is where LED reality is going to hit all of us hard standing halogen guys. Most of us want to retrofit all of our installations so that everything operates in the 10.8-11.8 range but the fact of the matter is LEDs are being pedaled by every distributor and sales rep in much the same way. Save costs with less wire, smaller transformers, fewer wirenuts or connections, less labor, etc, etc. 3 times in the past year alone I have been to LED classes or seminars and heard this rhetoric over and over again by Vista, Kichler and more. There own reps shoot this out there and more often than not so do the manufacturers.

    The bottom line is MOST of the LED sales reps are pedaling a product that has a large operational voltage range and it also has been proven that voltage differences in LED and Halogen do not perform in the same exact way. Halogen bulbs will always perform fractionally dimmer with every bit of voltage drop. The general consensus is that (without going below the high 10 volt range) 1 volt of drop isn't visible to the naked eye without extreme circumstances. LED performance from everything I have read and charts I have seen shows that some LEDs perform weaker at the highest acceptable voltage than they do in some cases being dialed down a few volts. In many cases these voltage ranges are anywhere from 4-6 volts and many of LEDs elite say that the general public would not be able to tell a difference in brightness and performance as long as it falls in their operating range.

    So after all that long wind, my point is you are right in that a lot of the industries "commercial" side is propagating the same information that you say you have been told. Then there is the other side of the coin where this rattles the foundation of everything that halogen installers have been doing for years with wiring methods and techniques. It's where the rubber hits the road because there will be the old school guys who are going to call these techniques "hack" work. Then the new led guys who have gotten their info from the same people you have will simply call us "over installers" who are balancing voltage and passing the cost on to the customer, when it's not proven to be a necessity and is just another added material (extra wire, extra connections) that could fail or be annoying.
  10. S&MLL

    S&MLL LawnSite Senior Member
    Messages: 751

    Couldnt agree more.

    I almost feel bad running out 250' of 12-2 cable. But Kichler says 9-15.

    Now with retro fit lamps I still wire for equal voltage. But if im installing Kichler I put it on the 15v tap and forget about it.

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