GFCI's

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The outlets in the back of the house are on a 20A GFCI. (Note to self: are there any other outlets on that same circuit that I need to chase down?)
Presently using them to light XMAS lights on one of the citrus trees. IIRC, each string is about 250W. With ~700W on the circuit, turning the breaker ON (i.e., using it as a switch -- instead of plugging/unplugging the load) causes it to immediately trip. Repeating the action in short order appears to get it to latch and remain latched (ON), indefinitely.
OK, so the surge when all the lamps are cold can increase the inrush current -- on the short term -- to levels that probably exceed the 20A limit of the breaker.
"In theory"
OTOH, in years past, I've run the circuit at close to its capacity (~10 strings) without this problem.
I've changed breakers (swapped with one feeding another circuit) and the problem persists.
[There are no leakage paths in the wiring OUTSIDE]
This suggests something in the wiring/fixtures. I'll start isolating outlets, tomorrow (dark here, now). Perhaps some insect (leaf cutter?) has opted to nest in one of the receptacles.
Anything else I should explore?
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On 12/1/2015 7:19 PM, Don Y wrote:

For those who didn't connect the dots, this is a GFCI *breaker*, not a GFCI *outlet* daisy-chained to feed the others.
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On Tue, 01 Dec 2015 19:26:18 -0700, Don Y

Does it trip with nothing connected? If not, it's not a dauber or anything on the main circuit. It has to be on the "load". Outdoor lights on a GFCI can be a problem - lots of possibilities for "leakage"
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On Tue, 01 Dec 2015 21:46:03 -0500, snipped-for-privacy@snyder.on.ca wrote:

If there is absolutely nothing connected, a neutral fault will not trip the GFCI. The slightest load will trip it tho. (it splits the neutral current) The other thing to remember is the faults are additive. If you are leaking a couple ma in a couple places, it will work until the total gets up around 5ma or so.
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On 12/1/2015 8:00 PM, snipped-for-privacy@aol.com wrote:

You're ignoring the fact that the breaker latches and HOLDS on the "second attempt". This suggests the problem is related to the change in load characteristics from the previous "brief lighting event" (fraction of a second when power surged into the lamps just before the breaker trips on the first attempt).
I'm at a loss to explain how anything else could appear and then disappear so readily!
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On Wed, 02 Dec 2015 00:13:36 -0700, Don Y

Unless the first application of power heated and "dried" whatever was causing the leak. Not a very likely scenario, for sure - but possibly just within the realm of possibility??
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On 12/2/2015 5:29 AM, snipped-for-privacy@snyder.on.ca wrote:

somehow cleared itself, then I wouldn't expect it to return hours later -- and the same scenario play out again. And, again.
I need to get out a watch and see how long I can wait *after* the first breaker close before the *next* closing will NOT hold. I.e., how long it takes the "problem" to reappear.
It it's on the order of a few minutes, it's unlikely that there's a "partial short" (dead bug, etc.).
Note that this is a dry time of year for us -- it's not like there are any external (or internal!) sources of water/moisture (other than body fluids of bugs :> )
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On Wed, 02 Dec 2015 07:29:45 -0500, snipped-for-privacy@snyder.on.ca wrote:

I have lots of GFCIs around here and it is not unusual to have one that tripped to hold after resetting a time or two. In the end, I always find a fault somewhere, usually something that is getting wet.
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On Wed, 02 Dec 2015 00:13:36 -0700, Don Y

If it is a clump of moist material, you may be cooking the moisture out a little with the first attempt. I am not a fan of the "inrush" theory of GFCI tripping. (or most other myths about what trips them) This is a simple comparison of the current between the hot and the neutral through a buck wound transformer. If you really think it is an overcurrent situation, plug it into a non GFCI circuit to test it
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On Wednesday, December 2, 2015 at 10:31:42 AM UTC-5, snipped-for-privacy@aol.com wrote:

+1
I also don't think the inrush current on 700W on lights could trip a 20A breaker. If it could, seems we'd have that problem all the time. 700W is only 6A worth of lights. I would think it's more likely something related to a fault, but why it would not happen on the second attempt, IDK.
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On 12/2/2015 8:31 AM, snipped-for-privacy@aol.com wrote:

Then, what is "rehydrating" the material for the *next* time it trips? No rain, here. Low humidity. No plumbing anywhere nearby.

That assumes the overload characteristics of the non-GFCI breaker are identical to that of the GFCI breaker. I have yet to find any documentation that calls out specifics -- for the GFCI breaker *or* the non-GFCI breakers located in the same panel!
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On 12/2/2015 10:56 AM, Don Y wrote:

This can't be the problem. Lights have been on all night. "Unplugged" them (i.e., don't muck with the breaker).
Wait *1* second and plug in, again. Lights come back on (i.e., breaker does not trip).
After a few seconds, unplug again. Wait 10 seconds and plug back in. Again, lights come on.
After a few seconds, unplug a third time. Wait 2 *minutes* and plug back in. Breaker immediately trips.
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On 12/2/2015 11:08 AM, Don Y wrote:

And, plugging the extension cord into a non-GFCI (inside the home) outlet -- keeping exactly the same amount of cord "wound" on it's spool as before -- does NOT trip *that* breaker.
I.e., the only thing that has been isolated as a result of these tests is the wire inside the walls and the actual receptacles; when that stuff is "in circuit", the breaker trips (either when turned on *or* when a "cold" load is plugged into it)
I'll try to remove all of the OTHER receptacles (places where things can infiltrate the wiring) and repeat the original test.
Then, replace the receptacle in question.
Then, move the load to a different receptacle.
Beyond that, I'll have to start opening wire nuts -- not something I like doing with #12AWG :<
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On Wed, 02 Dec 2015 11:53:14 -0700, Don Y

Not aluminum, by chance??
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On 12/2/2015 7:45 PM, snipped-for-privacy@snyder.on.ca wrote:

God, no!
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On Wed, 02 Dec 2015 19:56:17 -0700, Don Y

Just wondered with 12G - so they are 20 amp circuits - - -
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On 12/3/2015 2:34 PM, snipped-for-privacy@snyder.on.ca wrote:

Yes. Code requires them for kitchen countertop. etc. So, I just installed a bunch of them (bathrooms, countertops, outdoor and garage)
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On 12/02/2015 12:08 PM, Don Y wrote: ...

That's got to be a thermal problem in (probably) a particular lamp...eventually it'll burn out and let you isolate it or the base itself will fail.
--




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On 12/2/2015 11:54 AM, dpb wrote:

Unplug the three strings from the extension cord. Leave cord exactly as is. Take three *other* "identical" strings out and wire them in exactly the same fashion as the first set-of-three.
Turn on breaker. Trips immediately. Let it reset and turn it on a second time. Holds.
Walk around house to return to the point where the extension cord is plugged in.
Unplug. Wait a few seconds. Plug back in. Breaker trips.
(No, I'm not going to keep repeating this test to see how long it takes for the load to "deteriorate" between power applications. The fact that it tripped suggests the problem is not in the original three strings of lights -- or, coincidentally ALSO happens to be in the OTHER three strings, as well. And, no, I'm not going to drag out a third set of three... or a fourth set of three... :> )
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On 12/02/2015 1:08 PM, Don Y wrote:

...

...
Hadn't seen the duplicated test result...
I'd stick with the thermal issue and I'd suspect the cord if it's one of those w/ the indicator lamp built into the plug.
Did you ever isolate whether there were any other loads on this circuit besides these two (I think were mentioned early on?) exterior receptacles?
--




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