Different extension cord makes no change in symptoms.
(sigh) Sorry, but *I* can make a giant list of all possible
combinations and permutations or circuit breakers, circuit breaker
TYPES, extension cords, number of strings, WHICH strings, internal
wiring, ambient temperature, time between applications of loads,
then, try ALL of those variations to find the one(s) that work and
That's not troubleshooting. That's what (inept) mechanics/plumbers/PC
technicians/doctors/etc. do day to day:
"Well, let's try replacing the battery to see if that's the reason
your old battery died..."
(weeks later) "Hmmm... I guess it wasn't the battery as that NEW
one has also died! Let's try replacing the alternator!"
(weeks later) "Hmmm... what are the chances that the new/rebuilt
alternator was defective? Maybe the cable harness is bad..."
I'm looking for a *reasoned* approach to a particular cause and effect:
if *this* is the underlying problem, then this experiment will serve
to isolate and identify that as the cause.
Do you understand the difference between "a standard breaker"
and a GFCI?
A standard breaker has two connections: the power from the
distribution bus bar (usually a "snap on") and the *wire*
that feed the branch circuit ("load"). The branch circuit
picks up it's neutral and ground connections from a common
connection point shared among all branch circuits (as well as
the "AC line input")
A GFCI breaker has *four* connections: bus bar, load, NEUTRAL
and NEUTRAL PIGTAIL. I.e., the neutral wire feeding the branch
circuit connects to the breaker, NOT the neutral connection point.
Assuming you remove the GFCI and LEAVE IT DANGLING by it's
neutral pigtail, you still have to route the neutral for that
branch circuit up to the connection point for ALL the
neutral's in the panel. It's not "right next to" the breaker,
alongside the "hot" connection to the breaker!
Would you like me to also replace all of the RED lights in
the strings with BLUE ones? Maybe BOTH extensions are defective?
After all, both have been out in the same environment... maybe
they've both developed the same fault? A fault that HEALS
ITSELF when the lights have had a chance to warm up??
Maybe both GFCI breakers have failed in the same way -- despite
the fact that the other three located within inches haven't?
Sorry, I don't mean to sound pissy but "try this" is not what
I'm looking for. I want to approach the problem logically
not willy-nilly. I'd hoped someone might have *definitive*
information of problems like this instead of a litany of
hit-or-miss attempts. I.e., an explanation that reconciles
ALL of the observations I've posted.
sorry but that is a part of troubleshooting
Swapping around parts that you already have can be a very efficeint troubleshooting technique.
If we told you to go out and buy all new lights and new extension cords and new breakers and replace them all, that would not be troubleshooting, that would be shot-gunning.
If you prefer a more analytical approach, then go out and buy a dual trace oscilloscope, clamp on current probe and other assorted test equipment and we get then gather enough data to decide exactly what the problem is without swapping parts.
Sounds like we have nothing more to offer you in the way of help.
Be sure to come back and let us know what the answer turns out to be.
On 12/3/2015 12:36 PM, firstname.lastname@example.org wrote:
No, that's the lazy approach. That's the way auto mechanics start swapping
things (charging you for each "new replacement" -- even if it didn't FIX
the problem) out until they stumble on the "solution". Do they ever
work their way backwards, undoing all of the other (faulty) changes
they introduced along the way to definitively identify/verify that the
"final change" was, in fact, the real reason? Do they swap the "bad"
part back in to verify that the problem manifests, again?
This is just a lack of deductive reasoning capability. I see it in
how folks troubleshoot electronic designs, software, etc. all the time.
"Let's try this..." Then, if the device/program *appears* to work,
they content themselves with having "fixed it" -- with no basis for
belief that it is, in fact, (permanently/actually) "fixed".
"Well, it's working NOW..."
I guess in grade school we were taught "The Scientific Method"; form
an hypothesis, construct an experiment to test that hypothesis, then
apply it and verify the results.
And, you can run that process forwards or backwards, with predictable
outcomes in each case.
E.g., note that when I unplugged the lamps this morning and re-plugged
them, they didn't trip the breaker. Yet, plugging them "cold" caused
an instant trip. So, modify the experiment -- wait *10* seconds
before re-plugging. Then, 2 minutes.
Ah, now I have new information to assist in formulating a theory
(what, in the circuit, can "account for time"?)
You'll note I lamented the loss of my HiPot tester, up-thread??
Agreed. I'll return to my original plan of diagnosis.
I'll look into it this weekend. The lights won't be needed, again, for
several days so I can spend my time on other things that are more pressing.
_IF_ you did still have high quality test gear, I'd tend to agree with
your attempt at more esoteric trouble-shooting. Lacking that, the
likelihood of placing a measurement at the right spot with the facility
to catch the event is approaching zero...
So you might as well eliminate the one common component from the problem
before continuing down all those various ratholes you've previously
No, the logical approach is to imagine some agency (weather, infestation,
phase of the moon) that has asserted itself on the "system". Then,
think of what sorts of "changes" it could have made THAT WERE NOT
E.g., leaf cutter wasps laying eggs *inside* receptacles -- given that
I know these exist, here; water infiltrating a fixture (nope, no water
sources); something chewing on insulation (unlikely); etc.
I.e., look for a simple explanation that ties all the observations
together, consistently. Yeah, it could be all my bulbs have
a problem; it could be all my extension cords; all my GFCI's;
etc. But, it's not LIKELY that all that stuff happened AT THE
SAME TIME. I'd buy it if I had a problem with one string
of lights last year, another the year before, etc.
OTOH, something affecting *one* of the receptacles would make
sense -- *if* a reason for the other observations ALSO made
Since you are not paying for things you try that is not really a good
analogy but without the right test equipment, eliminating things in
the path is probably the only real way to go.
If I was really willing to "diagnose" this I would get a device type
GFCI, Disable the trip mechanism and look at the output of the
differential amplifier with a scope as I plugged in the lights, cords
etc looking for the one that is the offender. You could calibrate your
result using a pot and introducing a known fault value.
My bet is you will see this thing cruising in the 3-4 ma range so any
little glitch pushes it over.
On Thursday, December 3, 2015 at 7:47:53 PM UTC-5, email@example.com wrote:
I always start on the path of trying to fully diagnose the problem
instead of swapping parts. But anyone who has worked on cars has sure
had many times where they wished they had the dealers stock of parts
to try swapping something that is easily swappable to see if it fixes it.
Agree, that's the problem and why you're left with swapping. To conduct
the required tests is going to require some advanced gear that homeowner's
typically don't have. Even if I had it or had access to it, I wouldn't
waste my time trying to figure it out.
When I was fixing things for a living, my first question on a support
call was asking the guy who was working on it "Can you draw a circle
around the problem"? (in an acre of computer room floor, that may not
be as simple as it sounds)
Until you know for sure what box is failing, you really have to back
up and reassess.
It was surprising how many times that just getting your head put of
the box, turned a light on and got you on the right track.
Isolating the problem does not mean simply throwing parts at it. You
should learn something at each step.
In Don's situation,. I would start with a configuration that doesn't
fail and keep adding stuff until you break it.
Drag a known good space heater or heat gun out to the end of that
extension cord and try that, bearing in mind, the fault could be on
the neutral and that will not fail without a load.
On 12/3/2015 8:25 PM, firstname.lastname@example.org wrote:
There are no configurations that "don't fail" -- except the configuration
where there is no load present (and, thus, no need for power!).
My approach will be the opposite: remove things until it starts working.
Recall, everything worked last year. The extension cords and lights
have been stored "indoors" for all that time. OTOH, the outlets have been
exposed to the elements for the ~9 months (including a Summer and a Monsoon)
since then. So, any "changes" are most likely manifest in those items!
Wiring inside the block wall is likely not at risk as it is safely
hidden away (unless something likes chewing on vinyl!)
First, verify SWMBO's assertion that the toaster oven resulted in a similar
behavior. If that's true, it *tends* to rule out the lights and the
extension cord as possible problem areas (no guarantee, there, as they
could have other problems, as well). Then, reattach the lights as
the "nominal load" -- cuz I have lots of experience with them failing
(I don't want to end up with a situation where things SOMETIMES work
and that confuses any deductions made later).
[The idea of leaving an item used for food prep outside just doesn't
appeal to me! :> ]
Explore the upper limits on what the breaker will HOLD. If it trips
(when it would otherwise have held, based on prior observations),
I have another data point regarding the circuit's performance.
Is any loss of capacity a likely effect of aging? Or, is it dramatic
enough to suggest a fault, somewhere (keeping in mind that I'm
using the replacement GFCI, presently). Can a regular (20A) branch circuit
carry the same load without incident? (those breakers are OLDER, yet!)
Then, open all the Jboxes and have a peek inside. Any signs of "wildlife"?
Beginning at the box closest (electrically) to the panel, look at hot-neutral,
hot-ground, neutral-ground voltages under that fixed load (with breaker
in the "holding" state). Any IR drops should scale linearly; regardless of
how much wire there is between Jbox #X and Jbox #Y, there should be an
identical amount of neutral, hot and earth conductors! I can do this
from the exposed side of each receptacle -- no real effort required.
Then, start removing receptacles (in the hope that something may have set
up shop INSIDE one). At the same time, examine the contacts on each:
anything loose? Any signs of oxidation/corrosion?
Any changes in voltage readings when probing conductors instead of
Ultimately, I'll have to remove the outlet into which the extension
If this turns up nothing, start moving the load upstream. And, after
verifying operation at each such point, isolate the downstream
portion of the branch circuit (open wire nuts).
Eventually, I'll have a wire in the wall that connects the GFCI
to the *first* -- and ONLY -- receptacle.
On 12/3/2015 11:30 PM, email@example.com wrote:
(All of the outlets are "on" the house; presumably, you
meant "closest to the electric panel"?)
I've not tested each of the 5 outlets. They are spread over the
length of the house -- as well as around the side. I.e., I'd
have to *lengthen* the extension cord to reach them all.
I don't plan on continuing the "willy nilly" approach of jumping to
"try this", "now try that". Instead, I will approach the problem in
a more structured manner -- so each result adds to the data set
in a more organized fashion (instead of taking pot shots in different
But, that will wait until at least the weekend. I have many other
things that need to get done in the short term and the forecast suggests
I've got at least a week before temperatures begin to approach the
lows that are troublesome...
On 12/4/2015 8:28 AM, firstname.lastname@example.org wrote:
What if the nature of the load has an impact on the results?
E.g., say I plug a large power supply for that has an insane
turn-on transient in but idles at just a few watts (switching
losses). Smaller load but bigger turn on transient.
Or, drag out a longer spool of wire to use as the extension cord?
Or, try the toaster oven on one and lights on another?
Don't add variables to the analysis. Just come up with a
consistent test strategy and apply it consistently.
E.g., the second set of 3 strings that I dragged out to
mimic an "equivalent load" (as the first set that are
presently IN the tree) is only conceptually an identical
load. Making observations with one set in one case and
another set in another case isn't apples<->apples.
Even though it might (and quite probably is!) appear to
For the purposes if this discussion, a hair dryer would do just fine.
If it trips, you know you have a problem in the wall or receptacle
string. Then try it at the end of the extension cord. If still no
trip, there is a problem with your lights.
The idea that an incandescent light will trip a GFCI in normal
operation (no faults) is ludicrous. That tiny surge while the filament
is heating up is well inside the trip curve of any breaker I have ever
seen. It would certainly be less than the heat up time of a hair dryer
On 12/4/2015 1:43 PM, email@example.com wrote:
You've not been paying attention to the numerous "experiments"
I've already conducted.
E.g., different extension cord --> trips. Different light strings (same
cord) --> trips. Different GFCI breaker (same branch circuit) same
extension cord, same lights --> trips. "Cold" lights --> trips.
"Warm" lights --> no trip.
Extension + cold lights plugged into non-GFCI branch circuit --> *no* trip.
Ditto for different GFCI branch circuit, no trip.
I.e., nothing wrong with extension cord *or* lights.
Toaster oven (reported by SWMBO) plugged into same outlet WITHOUT extension
cord --> trips.
Problem is *clearly* with the wiring in the wall -- the only thing common
to all fault cases and NOT present in any of the non-fault cases! And,
only manifests when a load is present. Furthermore, only when the load is
significant ("cold" lamp strings)
The whole point of the discussion is that there *is* a fault!
Note that a much larger load (3X) had been present on the same branch
circuit last Winter with *no* problems for the entire season!
Forecast was for a cold night, tonight. So, rushed to get *something*
working -- regardless of an "explanation" -- in the hour I had before
As it was obvious that the problem had to be in the branch circuit,
I removed all receptacles, examined the routing of the conductors
within each Jbox, inspected all wire nuts, screw terminals, grounds,
etc. and, then, reassembled everything. Washed the "wet use" covers
just to make things look pretty (continuous sun exposure turns the
exterior paint to a powdery substance).
No "obvious" problems: no "bugs" falling out of the receptacles, no
corrosion on terminals, no exposed wires under wire nut skirts, no
nicks in insulation, no moisture in boxes, no mounting screws pressing
on conductors, no cables pinched in clamps, plenty of room in each box
(35 cu in), etc.
Circuit has been holding without any problem -- even in the (unexpected!)
rain that's been falling (and the "false alarm" for the cold weather!).
Added another 2 strands of lights (with a second extension cord) just
to push my luck...
Took the (inexpensive -- $1) precaution of fitting "child proof" plugs to
all unused outlets to ensure nothing *can* crawl into any of the outlets
in the future.
No way to ensure I can recreate the problem -- as I have no idea
what it *actually* was -- so I'll leave well enough alone and wait
for the next hiccup. Maybe buy some 20A receptacles to replace
these when I next have to go poking around in the Jboxes...
More likely that there was a neutral fault that was cleared when he
pulled everything apart and put it back.
Lots of mystery GFCI problems are fixed by an inspection that didn't
actually find a problem. Who knows what it was?
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