We're fully online using our 'B' power feed, however the APC UPS that caused this whole debacle is completely destroyed. Here's what we know:
* A routine transfer test was run on the UPS to verify its functionality.
* When the unit came back to normal after the test, it was making an abnormal buzzing sound.
* The unit was only reporting 11% load, much lower than the expected value.
* In an attempt to rectify the abnormal condition of the unit, we commanded it to cycle through internal bypass and back online. (It's a double-online conversion type, so this would cycle the inverter/rectifier.)
* As soon as the unit attempted to go into bypass mode, it made a very loud popping sound, followed by several cascading breaker trips that disabled the emergency 'B' feed.
* After executing an emergency power off on the unit, we cycled the breakers for the 'B' feed. Our network successfully recovered from a cold start on its own.
After all of this, we tried to bring the unit back online from a complete cold start, but it began making a repetitive clicking sound and started to emit a strong electrical fire smell. We immediately cut power once again, and removed the unit from the rack.
The unit in question is an APC SURT7500XLT.
Our total outage time from exploding UPS, emergency power cut, and cold start after cycling the 'B' feed was about 15 minutes.