Micheal:
You make a point worth consideration. I haven't had reason to use
an extension cord of over over a 125' with my outdoor GFCI socket, and
haven't had any problems. But, in your example I would also consider
two other possibilities: #1 - that you may have a small wear spot in
your cable, where water (moisture) may have worked its way into the
cardboard insulators that run the length of the cable, and since the
exterior of the cable is worn at this particular spot, the insulated
wires beneath that spot may also be starting to crack (or wear), and
you are actually getting leakage that is tripping your GFCI; this
would, of course, occur whether, or not, you have any load on the cable.
#2 - that you may have one of the GFCI's made in China, etc. that one
of the earlier posts mentioned was not well calibrated, and he found-out
that by changing the GFCI, the problem was cured. At any rate I presume
that you have tried a newer length of 250' extension cable.
There is also another possibility - that at the point where you
plug the extension cord into the GFCI that a leakage is occuring due to
build-up of dew, or other moisture. This could also be occuring at the
other end of the cable, or in the AC strip that you are plugging your
devices into; or a combination of these sources (5ma is not a whole lot
of current). - Len Gordon


Michael Smith wrote:
>
> Oftentimes, natural leakage thru the insulation of a long extension cord
> (read 50-100+ feet) or from a long inside-the-wall run to another outlet
> is enough to trip a GFCI (Ground Fault Circuit Interrupter). A GFCI
> works by "sensing" the current running thru the hot and neutral lines
> and comparing them. If the difference between the two is >5 ma
> (milliamp=1/1000 of an amp), GFCI's are supposed to trip. For example,
> if you are vacuuuming the car, there might be, say, 5 amps going down
> the hot line and 5 amps coming back up the neutral (I know, not exact,
> but for brevity's sake). This is normal. Say you step in a puddle
> while turning the vac off. Now, 5 amps might be running thru the hot
> line, but since you offer less resistance to the current than the
> vacuum's motor, that current is going to pass thru you into ground
> instead of going back up the neutral line of the cord. The current thru
> both wires is not equal now. The GFCI trips, hopefully in such a quick
> time that the 5 amps runs thru you for a *very* tiny moment. The real
> problem arises when there is a long run between the line (the GFCI) and
> the load (telescope, light, weedeater, vacuum). Insulation isn't
> absolutely insulative (is that a word?). There is always a small
> leakage from the hot line to ground (the actual "ground" wire, the outer
> insulation, the ground itself, whatever.) On a long run, this leakage
> can accumulate to a large enough amount to cause a properly working GFCI
> to trip needlessly. I have seen this happen many times. I have even
> seen a GFCI trip with 250' of extension cord plugged in and nothing
> else.
>
> Mike

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