GFI breakers nuisance tripping

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GerryR

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Having a problem with GFI breakers periodically tripping that are located within outdoor pool panel.One single pole feeds a Intermatic Mod:pX300 transformer which then output is 12 volt to wet niche underwater light nothing else on this circuit.The other breaker is a two pole feeding just a filter pump which runs off a built in timer which I noticed is running high in amps maybe this is tripping due to overload have to check into this.But the the light is a puzzle it only trips once in awhile according to HO.Checked the wiring is right,he says the system was installed about two years ago and hasn't been working right since.Appreicate any input I must be missing something maybe a moisture problem?
 
GFCI's do not nuisance trip. There is either a problem that the breaker is detecting, or the breaker is defective. Those are the only two posibilities. Test the GFCI using an inexpensive GFCI tester. If it checks OK, there is some problem in the wiring and/or moisture is getting into the system causing an intermittent problem. In this case the GFCI may be saving someone's life. Sorry if that is a nuisance.
 
Sure it could be a bad transformer or something else that's easy to fix but every time that I have had this problem it's always the same thing. It's always been a nick in the UF cable ( homeowner planting shrubs or something, digging in general ). Try trouble-shooting after a rain and use a megger, check the hot to ground and neutral to ground or you can use the method that I now use ( ask the homeowner where they have been digging ) it's faster. I'm sure that some day I get one of these problems that doesn't involve the use of a shovel but I'm still waiting.

At one apartment complex if found cable buried about two inches. I couldn't believe that it worked any of the time.
 
intermittent GFI

intermittent GFI

Sorry, I used the wrong word ' nuisance ' I did mean intermittent I'll have to be real careful when posting .
 
Suggestions, to try at different times, as a process of elimination:

First, use an ohmmeter to check for loss of isolation between the primary and secondary conductors.

Next, try disconnecting the primary wires from the transformer to see if it's the transformer.

Then, try disconnecting the secondary wires from the transformer to see if it's the light fixture.

The idea is to determine where in the chain the "weak link" is located.
 
Assuming the transformer windings are OK the GFCI can not be tripped by a ground fault on the secondary side of it.

I would suspect insulation breakdown between the GFCI and the transformer.
 
Spend an hour meggering all the connected equipment, and your culprit will quickly declare itself. The megger is an indispensable tool when troubleshooting intermittently tripping GFCI's and AFCI's.
 
Since R = E/I = 120/0.005 = 24K, I would think that a standard ohmmeter would suffice for this.
 
LarryFine said:
Since R = E/I = 120/0.005 = 24K, I would think that a standard ohmmeter would suffice for this.
Click to expand...
Then you'd be wrong. What voltage does you ohm meter operate at? What voltage(s) do the circuit(s) operate at? Big difference, eh?

You need the "punch" of the megger to find these intermittent leaks in cables and insulation breakdown in motor windings. Remember, your megger is an ohm meter that operates at a higher voltage. This is the beauty of how you can find and declare the bad apparatus and associated wiring quickly and decisively.
 
The Extech 403360 is one of many small digital meggers every technician can own. Maybe 100 bucks. No excuse for a trouble man not owning a tool such as this, in my opinion.
 
Is the wiring UF cable or did they run the wires for the light in PVC. It should go from the wet niche to the J-box, from the J-box to the transformer. Should come in on the load side of transformer. The feed should come from the GFIC breaker to the switch for the transformer. Check the switch.
 
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