Simple troubleshooting?

Discussion in 'Landscape Lighting' started by Stuttering Stan, Jun 12, 2012.

  1. Stuttering Stan

    Stuttering Stan LawnSite Bronze Member
    Messages: 1,504

    Can a nicked wire cause high amperage?
    Last weekend I installed some LED deck lights. Zig zagged wire through the posts. 1 fixture is no longer working. The meter reads about 22 amps and the wire is hot.

    Is a nicked wire grounding out to the wood posts causing the failure?
  2. Steve Atkinson

    Steve Atkinson LawnSite Member
    Messages: 94

    How many watts on the line? LED should create very low current draw. Remember watts divided by volts equals amps.

    Sounds like a minor short to me. Any possibility of short to ground? A nicked wire jacket may cause your situation. I have seen this where the installer was using a staple gun to place the wire under the deck frame and nicked the jacketing.
  3. Stuttering Stan

    Stuttering Stan LawnSite Bronze Member
    Messages: 1,504

    (16) 3w fixtures on about 30' of 10/2 wire. 48 total watts divided by 12 volts equals 4 amps.

    That narrows down to a nicked lead wire causing a 22 amp draw. I drilled the wire path through the 8x8 post then fed wire through. How I could have nicked the jacket is beyond me.
  4. Steve Atkinson

    Steve Atkinson LawnSite Member
    Messages: 94

    Are you seeing any noticeable decrease in light output? Also check your connections where the fixture wires join the feeder cables. And try comparing your actual voltage at the sockets, one close to the transformer, one at the end of the run. With LED your voltage should not vary too much.

    Good Luck with your project.
  5. INTEGRA Bespoke Lighting

    INTEGRA Bespoke Lighting LawnSite Platinum Member
    Messages: 4,102

    Disconnect the fixture that is not functioning and re-check your amp draw. If it returns to normal then you either have a wiring flaw or a fixture failure.

    Yes it is possible to have a nicked wire cause an ongoing short. This can be a very real safety issue and needs to be dealt with right away. What type of transformer are you using? It should have onboard secondary protection (breaker or fuse) that shuts the transformer off when a short circuit is present.

    Also, it is a very good idea to individually fuse those circuits that power up fixtures mounted to buildings and structures. An added measure of safety and security.
  6. LLC RI

    LLC RI LawnSite Member
    Messages: 149

    James... good point about fusing runs of fixtures attached to buildings/structures. I just installed a Nightscaping Savoy to a structure via a HATCH transformer. I know the transformer has internal protection but I was thinking of adding a fuse. I have 25 watts or so on the transformer so I am going to put a 3 amp fuse inline.

    Now... to Stuttering Stan.... just curious, why you used 10 ga wire for such a low current zone?

    I would agree with James in that it could be a bad fixture,

    OR perhaps the fixture mounting screws have pierced the lead wire to that fixture. What kind of LED Deck light are these? Could it be that the mounting screw pierced the wire within the wood post?

    Try removing the screws that hold that fixture on and see if your short changes. That kind of amp draw is most likely a short.

    Let us know what you find

    good luck

  7. David Gretzmier

    David Gretzmier LawnSite Gold Member
    Messages: 3,646

    I have seen this when the circuit is bridged "weakly" usually an errant strand of copper or two at a staple or screw where the wire has been nicked. thus the heat on the cable. I have also seen readings like this on a halogen bulb that has blown, not lit, but somehow is bridging the circuit and drawing amps on heat.

    the secondary protection only works on short circuits over 25 amps or so.

    starting on the non working light is the obvious, if the prolem persists after that, but after that I would disconnect the last half and check amps on the first 1/2. if you are good, then add the next 3 or so and check again. it helps narrow down which part of the wiring needs to be redone.
  8. Stuttering Stan

    Stuttering Stan LawnSite Bronze Member
    Messages: 1,504

  9. Stuttering Stan

    Stuttering Stan LawnSite Bronze Member
    Messages: 1,504

    I had an extra spool of 10ga from a hub job we did several years ago. I would have used 12ga if I had to buy wire for this project.
  10. Stuttering Stan

    Stuttering Stan LawnSite Bronze Member
    Messages: 1,504

    Guys, thanks for all the advice. I narrowed the problem down to a nicked lead wire inside the post. I installed new wiring and it amped at 0.5. If I can find the card reader, I'll post pics tomorrow so this can be a learning experience and I'd like to hear a critique from others.

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