Occassionally, we get a call about a potential power problem involving a computer that keep shutting off, even though it has a UPS (Uninterupptable Power Supply). The UPS converts its backup battery power to 120 volts when the power goes out. A simple, normal voltage drop in the house will trigger the UPS to try to run off the battery. If the battery or UPS unit is bad, you end up with a computer shut-down. It's normal for a brief voltage drop to occur when a refrigerator or an air conditioner starts.
Helpful Hint: Test your UPS unit by unplugging it from the wall outlet and see how long the system works. No UPS is better than a defective UPS.