Nice article. Please note that many AC noise/lightning suppressors including UPSs use capacitors from black to earth and white to earth (green). The currents should be balanced, but not always. Ul allows around a mA to flow to earth. Each filter adds. Even if an appliance is new, it could be a contributor.
The reason why these line-to-ground and neutral-to-ground RF capacitors cause unbalanced currents is that there’s a 120-volt potential across the line capacitor and close to 0-volt potential across the neutral capacitor. So at 60-hz there can be several mA line-to-ground leakage currents, but close to zero mA neutral to ground leakage. Note that UL allows up to 3mA leakage for these noise filtering capacitors. And that extra 3mA adds to any other line-to-ground leakage currents in the RV. Once they add up to 6mA it guarantees an upstream GFCI trip.
Through the years my crews have found GFCI’s receptacles not working properly during testing, especially those installed for long periods outdoors and damp locations. Yearly I test my GFCI’s at home and motorhome, recently my old Ideal tester gave up the ghost so I just picked up a Klein RT250 GFCI tester with a LCD screen that tests for correct polarity, ground, open neutral, and GFCI operation.
I think you have a typo in the second sentence of the paragraph describing how to increase the meter sensitivity by wrapping the green wire 10 times. I think you meant to say most meters are sensitive to 0.01A, not mA. Which in turn is 10mA. Good article!
Thanks…
Nice article. Please note that many AC noise/lightning suppressors including UPSs use capacitors from black to earth and white to earth (green). The currents should be balanced, but not always. Ul allows around a mA to flow to earth. Each filter adds. Even if an appliance is new, it could be a contributor.
The reason why these line-to-ground and neutral-to-ground RF capacitors cause unbalanced currents is that there’s a 120-volt potential across the line capacitor and close to 0-volt potential across the neutral capacitor. So at 60-hz there can be several mA line-to-ground leakage currents, but close to zero mA neutral to ground leakage. Note that UL allows up to 3mA leakage for these noise filtering capacitors. And that extra 3mA adds to any other line-to-ground leakage currents in the RV. Once they add up to 6mA it guarantees an upstream GFCI trip.
Through the years my crews have found GFCI’s receptacles not working properly during testing, especially those installed for long periods outdoors and damp locations. Yearly I test my GFCI’s at home and motorhome, recently my old Ideal tester gave up the ghost so I just picked up a Klein RT250 GFCI tester with a LCD screen that tests for correct polarity, ground, open neutral, and GFCI operation.
I really like the Klein RT250
Really appreciate the clear concise description of how the GFCI works and how to trouble shoot it.
Excellent article, especially the troubleshooting tips! Delightfully helpful. Thanks for the article and all the work you are doing.
Thanks. I know this might seem totally over the head of a casual RV owner, but electricity can get pretty complicated.
I think you have a typo in the second sentence of the paragraph describing how to increase the meter sensitivity by wrapping the green wire 10 times. I think you meant to say most meters are sensitive to 0.01A, not mA. Which in turn is 10mA. Good article!
Thanks for the catch! 😁