On 6/5/2015 2:16 PM, Michael Hennebry wrote: > On Fri, 5 Jun 2015, g wrote: > >> On 06/05/2015 03:43 PM, John R Pierce wrote: >>> On 6/5/2015 1:33 PM, Michael Hennebry wrote: >>>> It's a desktop in an old house. >>>> The outlets have ground-fault protection, >>>> but the third prong is ungrounded. >>> >>> not sure how GFI would function at all without a valid ground, unless >>> the GFI is wired to neutral, which is dangerous on its own. > > As I understand it, GFI sums the currents going into each prong. > If the sum is not close enough to zero, it breaks the circuit. I thought it monitored the current on the ground pin, and if there is ANY significant ground current, it disconnects the line and neutral pins, shutting the socket off.. -- john r pierce, recycling bits in santa cruz