Trouble with Low Voltage lighting transformer

Discussion in 'Landscape Lighting' started by CitznFish, Jul 19, 2011.

  1. CitznFish

    CitznFish LawnSite Member
    Messages: 12


    My transformer keeps tripping its internal breaker when my lights come on. This transformer worked well for about 4 years. Now whenever the lights come on they will stay on for a little while than the transformer will trip it's circuit breaker. I have checked the connection of the lighting wire to the transformer and it's in excellent condition. I have looked for a break in the wire where the wire isn't buried and can't see anything. If I turn the transformer on AND have my lights unplugged from the transformer it will not trip the internal circuit breaker.

    I do not want to dig up all my buried wire. :(

    Can this be an issue with the transformer going bad? It only does this under load and it's not immediate. Last night it happened after about 10 minutes. The night before, after about 2 hours. The night before that after about 30 minutes.

    Any idea on how to pinpoint if it is the transformer?

  2. Lite4

    Lite4 LawnSite Gold Member
    Messages: 3,187

    Have you edged any of your beds recently or dug around where any of your cables are?
    Posted via Mobile Device
  3. CitznFish

    CitznFish LawnSite Member
    Messages: 12

    Nope. I pulled some plants out around an area with a light but I looked for a broken wire there and found nothing. I was thinking of cutting the wire there to see if that solved it, but really didn't want to go that route...
  4. klkanders

    klkanders LawnSite Senior Member
    from Midwest
    Messages: 849

    Tim is on the right track. I will add this. Seems to me if it was a short or wires crossing together it would trip the breaker right after putting power to it. But as you stated its been random. You somehow have more resistance now either from wire or lamp load than you did when system was running properly.Have any higher wattage lamps been added or any wiring changed? Could any of the connections have allowed water to wick into any of the wire causing corrosion? Do you have just one home run wire to the transformer or more? Start by disabling some of the fixtures or runs to narrow the problem down. Good Luck!
  5. CitznFish

    CitznFish LawnSite Member
    Messages: 12

    Thanks for the reply.

    I have only one wire to the transformer.

    The bulbs are all the same wattage as when they were new. I haven't upped the wattage.

    I don't think any connections could have corroded.

    I guess I will go the hard route and start unplugging fixtures but I'm not sure how that will help, unless it is a bad fixture.

    I was hoping it was the transformer going bad. Guess there isn't a real way to test this?
  6. INTEGRA Bespoke Lighting

    INTEGRA Bespoke Lighting LawnSite Platinum Member
    Messages: 4,102

    You are in luck since you live in Simi Valley. I would give Mike Gambino a call at Gambino Landscape Lighting. He is one of the best in the biz. and I am sure he would be able to help you out.
  7. Lite4

    Lite4 LawnSite Gold Member
    Messages: 3,187

    When you say "unplug" the fixtures, it sounds as if you had used pierce point connections when you installed them. If this is the case, there is a very high probability of corrosion (and increased resistance) in the wiring.
  8. LLC RI

    LLC RI LawnSite Member
    Messages: 149

    What kind of lamps in the fixtures? Some lamps are more prone to socket failure. Namely, single contact bayonet. Sometimes, the mica disc softens and the center contact pin comes in contact with the shell. This phenomenon can occur as heat builds up.

    If, as suspected by others, you have these fixtures connected to the main cable via pierce pin 'quick connectors', I'd recommend that you rewire each fixture. At the point when you are doing that, use a meter and check each fixture for a bad socket, by removing the bulb and testing for resistance/continuity. With no lamp, there should be no continuity.

    What you describe as an overload could also be a bad connection. You say you only have one wire coming to the transformer, but do you have a main splice nearby that connects multiple runs?

    Also, what kind of transformer? I have had issues over the years with the white toggle style magnetic breaker that would be in any transformer made by MDL. This would include older ones from hadco, coppermoon, and others. In my experience, I have found that the yellow crimp connectors on the back of the breaker, would loosen over time and heat, and cause arcing. This would result also in a randomly tripping breaker.

    Good Luck.. let us know what you find.
  9. CitznFish

    CitznFish LawnSite Member
    Messages: 12

    Thank you for all the input everyone. I ended up replacing the transformer and it's working again as it should be.
  10. Don Rice

    Don Rice LawnSite Member
    Messages: 1

    I have a Malibu 200 watt transformer that was doing the same thing. When you reset the circuit breaker, the lights would stay on for about 5 minutes and trip the breaker.

    I checked the bulbs, wire, and connections thinking that the hard winter might have cause a break. Everything was good.

    I disconnected the power, took the transformer off the wall, and disconnected the wire from its leads.

    There are 6 small Phillips head screws (3 on each side) that hold the plastic front cover to the metal frame. After you remove them, the front cover will separate from the frame. Be careful of the small wires connected to the front switches.

    The circuit breaker has two spade connectors attached at the back. Remove them. A plastic nut holds on the outside holds the circuit breaker in place. Take that off, and the circuit breaker will slide out easily.

    I found an exact match for the circuit breaker at my local Ace Hardware store where it is called a "Thermal Circuit Breaker." It only cost $8.

    Put the new circuit breaker back in place with the new plastic nut. Reattach the spade connectors. (Note the circuit breaker has each connection labeled as line and load. The load is the shorter wire that goes to the connection for the lights. The line is the longer wire that comes from the transformer coil.)

    Reattach the front cover with the 6 screws. Reconnect the lighting wire to the terminals. Remount the transformer, and plug in the unit to the outlet.

    Everything works great again.

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