We have multiple GFCI cords, such as this one (the GFCI is not an outlet). When plugged into a certain outlet, they all consistently trip with any load higher than a few watts. When plugged into any other outlet, they work fine.
Shouldn't this be physically impossible? If a GFCI just measures the current difference between the two halves of the circuit, no configuration on the supply-side should ever cause it to trip, right?
(For example, a ground-fault inside the outlet would cause the voltage/current to the GFCI to drop, but the current coming in and going out should still be the same, by Kirchoff's current law)
I assume this is caused by some nuance of GFCI implementations I don't know about, which is why I'm asking here.
- An outlet tester shows the outlet is wired ok, so the hot/neutral aren't swapped.
- When using the outlet tester with the GFCI, the GFCI does not trip. But various loads ranging from 250 W to 1500 W all cause it to trip. Those same loads with the same GFCI don't trip in other outlets.
- I've tried multiple GFCIs with multiple devices, all with the same results.
- The outlet measures 120V
[Edit] One of the GFCIs seems to know when it's plugged into the bad outlet, even with no devices plugged in. When plugged into the bad outlet, the 'test' function on the GFCI does not work. When plugged into any other outlet, it does. The GFCI still trips with any device plugged in, which again should be impossible...
[Edit 2] This should not have been migrated. It is an electronics question, not a DIY question. Sigh.