I have a 3000 watt UPS in my office with two computers attached to it. I went ahead and put two GFCI extension cords onto each unique circuit breaker on the back of the UPS, and then attached the electrical outlets for each computer to each of those GFCI extensions. My thinking was that if someone accidentally cut a cord and created an electrical shock hazard, that the GFCI logic would immediately shut off just the affected equipment.
One of the two computer/monitors is shutting off about once every two days now. It's clearly the the GFCI logic because when I examine the GFCI indicator, all lights are turned off. I hit the Reset button on the GFCI, and the circuit comes alive again.
What would cause GFCI to trigger? I doubt that the cord or PC/monitor is compromised. Maybe this indicates a potential overload condition on this one circuit breaker on the UPS?
Alternately, maybe my assumptions behind using a GFCI *behind* a UPS is faulty? Maybe a GFCI can only work correctly when attached directly to the wall socket?
Finally, maybe the UPS itself just doesn't have an attachment to true ground, and I need to attach a separate grounding cable? How would I prove that the wall socket's ground is going to true ground?