GFCI Failures + Gadgets

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Went outside to add another electrical circuit at the BBQ and discovered that all of my nice wire-tagging had faded to non-readable.
So I couldn't figure out which common went with which hot.
Then it dawned on me to simply trip the GFCIs which releases *both* hots and commons so a simple ohm-meter check would do the trick.
NOT! Both GFCIs wouldn't trip when I pressed the test buttons :-(
Went to Radio Shack and bought a Receptacle/GFCI tester for $5.99.
At the same time I noticed a gadget to locate breakers... bought it also ($29.95).
Went home and tested the GFCIs... both have failed :-( Tester was verified on some indoor GFCIs... it would trip them.
Both bad units are outdoors, so maybe it was the heat (they both face the western sun... it gets over 120F here :-). Any other ideas about why they fail?
The breaker locator is neat... plug a sender unit into an outlet, then scan the breakers... works like a champ.
...Jim Thompson
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Demonstrated is but another reason why homes require a 'whole house' surge protector on each incoming utility wire. GFCIs are electronics that contain effective protection. Protection that can be overwhelmed if incoming transients (ie lightning) are not earthed before entering the building. IOW GFCI failure is a symptom that a whole household of appliances have ineffective protection. Maybe the home does not have the proper central earth ground as well as no 'whole house' protector. But GFCI failures can be created by incoming, common mode transients. I have been told this type of failure damages as many as 50% of all GFCIs in central FL.
$5+ for a GFCI tester? Its nothing more than a switch and maybe a 15K resistor that connects hot (black) wire to safety ground (green) wire. That same tester is what the TEST button does - already inside the GFCI.
Jim Thompson wrote:

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There *is* a whole-house surge-protector. All the GFCIs inside check out OK, so I'm guessing it's a heat issue only.

I earn $5.95 in less than 2 minutes designing ICs. I don't build *anything* anymore except for fun or if the function is unavailable... plus this tester also verifies phasing and no lost connections ;-)
...Jim Thompson
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Just because some GFCIs are working does not mean a surge could not exist. These GFCIs are outside. Using buried wire? IOW if the exterior (exterior) GFCI made a better earth ground than the central earth ground for 'whole house' protector, then surge would also use GFCI as a destructive path to earth. If mounted on side of building, then this scenario is not so likely.
Operating temperature for older versions GFCI chips is typically up to 70 degrees C. Chip consumes near zero watts. IOW heat is not a likely reason for failure for those type. Have not seen datasheets for newer type GFCIs. But then is that receptacle getting so warm that IC would exceed 70 degree C?
How good (and short) that that ground for the 'whole house' protector. Is there any good earthing path via those GFCIs? Perhaps are those GFCIs located on the far side of the building?
Jim Thompson wrote:

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In direct sun during hot weather? That wouldn't be surprising at all.
BB
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Not exactly the same. As I understand it the internal GFCI test switch will work without a ground conductor connected because the connection is effected between the hot conductor after the GFCI Device, and the Neutral before the GFCI. The aftermarket testors wont trip the GFCI Device without a ground conductor connected to it.
There are also usually indicators that allow some level of troubleshooting as to the proper wiring of a receptacle.
Louis-- ********************************************* Remove the two fish in address to respond

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On Sun, 16 Nov 2003 00:39:10 GMT, "Louis Bybee"

It will, the test button on a GFCI usually, through a resistor, connects the GFCI protected hot to the unprotected neutral.

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will
effected
the
If you read my answer above, this is exactly what I indicated. In the second part of my reply I suggested that an aftermarket tester (not the one on the GFCI) wouldn't trip a GFCI where there wasn't a ground conductor connected to it (try it).
Louis-- ********************************************* Remove the two fish in address to respond

troubleshooting
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On Sat, 15 Nov 2003 20:18:15 -0500, Gary Tait wrote:

That's just the same as loading the circuit, it won't work. GFCIs monitor current in *both* hot and neutral, which should be the same.
You need to create an imbalance current by introducing a resistance between hot and *ground* 5mA might do it. 30mA _must_ do it, or the protection is no damn good.
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If you connect to the neutral (before the circuit) and to live (after), then that works.
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Does the use of a GFCI outlet help in a situation where is circuit is merely overloaded, but not short-circuited?
THX Wayne
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On Mon, 17 Nov 2003 13:11:30 GMT, Wayne Boatwright

Help how? A GFCI provides no more voltage or current, or protection against H-N overloads and short circuits.
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The circuitry internal to a GFCI Device is specifically designed to sense, and trip, in the event of an imbalance in the current flow between the current carrying conductors (the current in one has to be within 4 to 6 ma of the current in the other), the Hot and the Neutral (120v), or Hot and Hot (208 - 240v USA). As long as the current is balanced it makes no difference to the GFCI Device if it is overloaded, or shorted between the current carrying conductors. If there is no imbalance, the GFCI Device is unlikely to trip even in the event of a direct short between the current carrying conductors unless a portion of the current finds a path other than the intended one.
Louis-- ********************************************* Remove the two fish in address to respond
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wrote:

Thank you...
Wayne
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On Mon, 17 Nov 2003 13:11:30 GMT, Wayne Boatwright

No. A GFCI is not an overcurrent protection device - it just protects against leakage current as indicated by a difference between supply and return currents in the circuit.
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wrote:

Thank you...
Wayne
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GFCIs monitor current in hot and neutral *after* the (unprotected) line input. You can create an imbalance current by introducing a *finite resistance[1]* between protected (load side) hot and *unprotected (line side) neutral*. That's how the GFCI test button works, with no connection to ground (witness the 2 prong GFCI in hair dryer plugs). It is not the same as simply loading the circuit. A GFCI tester that could not access the unprotected neutral would have to use some other path, ground being the most convenient.
%mod%
[1] An open circuit is infinite resistance.
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wrote:

connects
monitor
There is no such thing as "infinite" resistance!
With the appropriate instrumentation any resistance could be quantified. What you think of, or even measure, as an open circuit, is merely a circuit which has exceeded your, or your instrument's, ability to measure. :-]
Louis-- ********************************************* Remove the two fish in address to respond
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I read in sci.electronics.design that Louis Bybee <louistroutbybee@comca
Failures + Gadgets', on Wed, 19 Nov 2003:

Quite right. I have a very old (well, around 50 years) Twenty Million Megohmmeter. I don't suppose the EF37As still have low enough grid current. (;-) I keep it for the huge meter, which I can't bear to throw away.
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Little surge protectors offer very little protection against lightning. That is a common misconception.

indeed.
Regards, NT
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