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Transformer tripping

Discussion in 'Landscape Lighting' started by Zohan, Jul 11, 2013.

  1. Zohan

    Zohan LawnSite Member
    Posts: 136

    Installed a system 2 years ago, which includes a vista mt-300 transformer.
    There is a circuit breaker on each tap but also a primary circuit breaker. The primary breaker has been tripping. It was reset and tripped again about a day later.
    This is all info i am getting relayed to me before i go onsite which is about an hour and half each way, so id like to figure a plan of action beforehand.
    First, anyone have info for a specific problem?
    Second, any tips or tricks with this? Its been working 2 years...
    First thought is disconnect one of the 3 zones, reset breaker and see if it trips, repeat process until i find the faulty zone then try to figure out from there. Problem is that its so far to go back day after day after day...so im hoping someone will have related experience that will shorten my process.....

  2. Classic Lighting

    Classic Lighting LawnSite Senior Member
    Posts: 492

    Take amp measurements for each zone and assess if there is a short. Consider swapping out the tranzformer if you are stumped.
  3. Zohan

    Zohan LawnSite Member
    Posts: 136

    Thanks. Whats throwing me off is apparently it doesnt trip right away but the next day....
    Will do
  4. INTEGRA Bespoke Lighting

    INTEGRA Bespoke Lighting LawnSite Platinum Member
    Posts: 4,102

  5. Zohan

    Zohan LawnSite Member
    Posts: 136

    No, this was done just before I switched to LED
  6. Lite4

    Lite4 LawnSite Gold Member
    Posts: 3,113

    Once you take amp readings on everything, and if they come up normal there a couple things to consider.

    1. Does your client have an irrigation system? Does it only trip after they water or after a rain storm- indicates open insulator jacket- Has anyone been doing any digging since you noticed it started tripping?

    2. If not, then the next thing I would consider is the fact that you may have a weak breaker in the transformer. I have had these from time to time (not very often, but it does happen), I was able to replace the breaker in the transformer and no problems after that. These were MDL transformers, so it was easy getting into the guts to replace it. Some transformers are not that way though. If all things check out normal on the amp side, I would be suspicious of the tranny and drop another one on there. (especially from an hour and a half away.)

    Good Luck!
  7. Zohan

    Zohan LawnSite Member
    Posts: 136

    Thanks. #1 is what I was thinking first. They have irrigation. I asked if anyone has been digging but haven't received a response yet.

    Either way, it's a minimum of 2 trips unless I find something on first trip. Even if I test the amperage it might not show right away. This could be trying to find the needle in a haystack. Especially if it only trips when it gets wet.....
  8. Lite4

    Lite4 LawnSite Gold Member
    Posts: 3,113

    True, I invested in a Pulser, ground fault locator years ago just for this very reason. It has saved me a ton of grief in the past.
  9. LLC RI

    LLC RI LawnSite Member
    Posts: 149

    ZOHAN... long time no talk!!... So let me chime in here...
    It's odd that the primary breaker is tripping without any issues on the secondary breakers. The scenario could be that there is something getting into the transformer- mouse, chipmunk, etc. that has eaten some insulation and is causing that to happen. Second scenario is that the secondary breaker is bad, not tripping when it should, and thus the primary trips, but only after the core heats up enough to cause the trip.

    So as the other guys said.... check the amperage of each run and make sure you are within your range for the circuit. ( SOmeone could have put 50 watt lamps in where there should be 20's)

    If your lines measure out ok, test the secondary breaker by creating a short with a loop of wire... see if that causes the secondary breaker to trip. If not, then the problem could be the secondary breaker.

    Next, check the voltage at the outlet. I'm doing some math here and wonder if the transformer is being fed with lower than normal voltage on the line voltage side, if the current draw of the primary fuse/breaker would be elevated. ( Maybe their AC or something is kicking on and drawing the voltage down)

    WHen you make the trip, bring a spare 25 amp breaker or fustat and socket... also.. bring a 5 amp buss fuse with holder to use on the primary side... in case you find either breakers not to be working properly.

    As a test, you could disconnect the primary breaker and put the buss fuse in it's place.. see what happens.

    I'm a little puzzled because you say it's a 300 watt transformer that has multiple breakers on the 12 volt side??

    If you end up opening the transformer cabinet, check the push on terminal connectors on the breakers. I've had a lot of situations where that stay-kon connector gets loose, hot and eventually loosens over time which creates arcing... but then again.. that would result in the primary breaker tripping.

    Well.. good luck... hope this helps.. keep us posted

  10. Zohan

    Zohan LawnSite Member
    Posts: 136

    Thanks for all the info.....
    I was onsite yesterday. I didn't have to troubleshoot much though....
    Seems the irrigation guys cut the wire....an electrician fixed with romex running the line above ground, and spliced with wire nuts and wrapped in electrical tape. The splice was just sticking above ground and the whole area was swampy so I know there are sprinkler heads in the area, and most likely wetting the splice.....?

    What do you think?
    I ran new line and direct burial connectors.....I have not heard anything yet...

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