Low volt Transformer keeps throwing breaker.

Discussion in 'General Electronics Chat' started by David Lauch, Oct 18, 2014.

  1. David Lauch

    Thread Starter New Member

    Oct 18, 2014
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    I have installed a switched outlet to control two strips of LED tape lights. The 180 watt transformer plugs in to this switched outlet. Three other outlets are also powered by the 20 amp circuit serving the transformer, however, no load has yet been plugged in to these outlets. I can plug my electric drill into any of these outlets including the outlet that is to serve the transformer. All work fine and the breaker doesn't throw when I run my drill. I can plug the transformer into an outlet on a different circuit via extension cord and the transformer works fine, tape lights come on and all is good. I have verified the transformer outlet is getting 120 volts using my voltage meter. The transformer 120/240 switch on the transformers circuit board is switched to 120. I am baffled as to why the breaker keeps throwing. Please help if you can.
     
  2. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Is the branch circuit protected by a GFI breaker, or is one of the outlets on the circuit a GFI outlet?
     
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  3. David Lauch

    Thread Starter New Member

    Oct 18, 2014
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    The breaker has a red button on it that says TEST.
     
  4. MrChips

    Moderator

    Oct 2, 2009
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    I think MikeML is on to something. Your GFI is doing its job. You have a ground fault.
     
  5. David Lauch

    Thread Starter New Member

    Oct 18, 2014
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    Thanks guys! That was it. I replaced the breaker with a standard and now it works perfectly!
     
  6. MrChips

    Moderator

    Oct 2, 2009
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    No! No! No!

    Your GFI is saying you have a ground fault. A standard breaker gives you no protection against faults.

    Determine that the GFI is faulty or fix the fault if the GFI is working properly.
     
  7. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    A lot of new-fangled 120Vac to 12Vdc switching power-supplies have RFI suppression capacitors (in the form of a common-mode choke) on their 120V line input side. The transient charging current into the capacitors can cause an overly-sensitive GFI to trip when the cord is first plugged in.

    The correct solution is to try another GFI breaker, not eliminate it...
     
  8. David Lauch

    Thread Starter New Member

    Oct 18, 2014
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    Please confirm...the reason for trying another GFI breaker is to find out whether the original GFI breaker was just too sensitive or if there was truly a ground fault? There is no other reason to connect the transformer to a GFI breaker if it is not near water? Would plugging the transformer in to a GFCI outlet accomplish the same test?
    Thanks for your help!
     
  9. MaxHeadRoom

    Expert

    Jul 18, 2013
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    A test for ground current, power the transformer ungrounded, measure from the frame to earth (ground) , if there is a voltage, place a 1k-5k resistor from frame to earth and see if the voltage is still present, if it is, there is leakage on the transformer.
    Max.
     
  10. David Lauch

    Thread Starter New Member

    Oct 18, 2014
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    This is way over my head. The transformer is mounted in my joist space eight feet above my basement floor. The transformer is plugged in to a grounded outlet mounted right next to the transformer. What is a 1k-5k resistor? How do you measure from the frame to the earth? I assume you mean measure voltage not distance?
     
  11. Lestraveled

    Well-Known Member

    May 19, 2014
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    A GFI breaker is there to save your life. You have removed it. Not a good thing. From your description it appears either the GFI is defective or the LED transformer is defective (or non-standard.) I am leaning towards the LED transformer.

    The outlets in your bathroom have GFI breakers on them. Plug your LED transformer into the outlets in your bathroom. If your bathroom GFI trips then the LED transformer is bad. It it works fine in the bathroom, then your basement GFI is bad.
     
  12. Brevor

    Active Member

    Apr 9, 2011
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    When a GFI breaker is installed in a breaker panel this is usually because that circuit is feeding an outlet in a possibly wet location, such as an outdoor recepticle. If you remove the GFI you may have an unprotected outlet somewhere. Also it may violate the electrical code.
     
  13. Brevor

    Active Member

    Apr 9, 2011
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    In my house the bathroom outlets are all tied to a common GFI in the breaker panel. If Davids house is wired the same as mine he may have removed the GFI protection from his bathroom outlets.
     
  14. David Lauch

    Thread Starter New Member

    Oct 18, 2014
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    The GFI breaker I removed used to power a Jacuzzi in my master bath which I have removed during my remodel project. I'll plug the transformer in to my GFI bathroom outlets to verify if the transformer is good.
     
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