If the site wiring fault LED indicator (small red light on the back of the Smart-UPS) is lit on your UPS, this means that there could be a site wiring fault in the building or in the outlet providing power to the UPS. The site wiring fault indicator doesn’t mean there’s something wrong with the UPS, usually it’s one of the following:
1. Overloaded neutral wire (>5vdc measured between Neutral and Ground)
2. Reversed polarity (hot and neutral wires are reversed)
3. Missing ground wire (also includes using a 3 prong to 2 prong adapter)
If the site wiring fault indicator is lit up, the wiring in the facility should be inspected to make sure everything is wired and grounded properly. This could be a shock hazard so it’s important to address it and get it corrected as soon as possible.