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LED problem, Need help please

Discussion in 'Landscape Lighting' started by bobbyc1980, Nov 4, 2011.

  1. bobbyc1980

    bobbyc1980 LawnSite Member
    Messages: 11

    Hi guys. I installed 10 LED bullet lights at a clients house. I used a Hadco 300W transformer, 10 bullet lights with 3W LED MR16 bulbs in each and 12-2 wire. The problem is that the 2 first lights are working fine, then the next one on the line is very weak, and the ones after that dont work at all. Everything worked great for a week and then this happened. The first light is 30 feet from the box. It is registering only 11.1 volts. I have the transformer on 15V tap by the way. The weak one is the third one on the line. Roughly 80-100 feet down the wire from the box. It is only pulling 6.5 volts. The last one on the line is 400 feet of wire from the box and is only pulling 4 volts. When I checked the transformer with the meter, I tested the 15volt tap. It only showed 14. Each tap was one less volt than it should be. Is the box my problem? This is my first LED project. Any help would be great. Thanks
  2. INTEGRA Bespoke Lighting

    INTEGRA Bespoke Lighting LawnSite Platinum Member
    Messages: 4,102

    My first suggestion is to remove the LED lamp from the 3rd fixture on the run and see what happens. I would suspect that the lamp is faulty and causing issues beyond that.
  3. JC Lighting

    JC Lighting LawnSite Member
    Messages: 31

    Check the amps on the home run, the reading should be around 2.5 amps. My guess is that it will read much more. If this is the case then, like James says, start with the first bad LED and check them all one by one. Let us know what you find. Lot of variables but I guessing one of the LED's has failed pulling an extra draw on the line reducing the voltage below the threshold of operation for the other LED's. I don't think the box is your problem.
    Let us know.

    Jim C.
  4. steveparrott

    steveparrott Sponsor
    Messages: 1,275

    Bobby, this is a very interesting case study. It does seem strange that the voltage losses are so severe. As with the others, the firat thing that comes to mind is that you have one or more lamps that have failed and are nearly or totally shorted out.

    However, if you find that all the LED's are functioning normally when correct voltage is applied then you need to consider the following:

    Wattage: While the manufacturer may claim 3 watts per lamp, keep in mind that they may actually be more. Also, just as with incandescent lighting, when you increase the voltage, the wattage also increases. To be on the safe side, base your calculations on 5 watts for your 15 volt input.

    Power Factor: I keep bringing this up. Depending on the driver electronics, the power factor can be anywhere between 0.7 and 0.9. Divide your wattage by power factor to get volt-amps - base your calculations on that - not watts. Also keep in mind that power factor changes with voltage - it can either go up or down with increased voltage.

    Daisy Chain: Many don't realize that in a daisy chain configuration, the voltage at each fixture is dependent on the load for the entire chain after the fixture. You have a really long chain (400').

    By the way, your figures make sense for an 18-watt (VA) lamp - that seems unlikely so the bad lamp scenario is probably right.

    By the way, my CAST Daisy Chain Calculator needs work, click here for pretty good one from MN Power Limited.
  5. bobbyc1980

    bobbyc1980 LawnSite Member
    Messages: 11

    Thanks guys for all of the help. Weird thing happened over the weekend. The client called me and said they all came on normally again. But an hour later they went back to the way they were. Very strange. Im going to head back over and swap out bulbs. Hopefully that will fix it
  6. steveparrott

    steveparrott Sponsor
    Messages: 1,275

    Bobby, any update on this?

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