Been there, done that, got the blasted tee shirt
Once, as a secure US military installation, which was key in all current wartime communications, the technical control facility manager decided to take the building's UPS offline and go direct to mains power. The unit being active:active at all times. The reason was simple and necessary; replacing a room full of dead UPS batteries.
Regrettably, he only skimmed the instruction manual, didn't want to wait for the installation electrician and flipped the twisty switch.
The entire server all went down hard. When he put the switch right (he was one position off from the correct setting), one key rack didn't come online and remained dark.
At the time, this BOFH had been wearing the information assurance hat, but am an experienced BOFH and also a certified electronics technician in industrial automation and robotics. So, reading industrial electrical blueprints is ancient news to me.
"Where is the electrical blueprint?"
Spreads several blueprints out on the floor, kneeing, tossing the incorrect diagrams aside, I rapidly locate (paraphrased, to protect NDA information), "Ah! Circuit breaker 57A, in bank 12F. Where is it?"
Predictable look of confusion and consternation and disclaimers of such arcane knowledge.
A swift heel and toe express around the battery/UPS room located the breaker - conveniently located behind a one-off bank of several hundred batteries, seriously out of view and traffic. Sure as can be, the breaker was tripped.
There was one chance in three that I'd flip that breaker on my own authority, on a US military base, and worse, in wartime. Slim, fat and none.
"OK, here's the culprit. *I* am not going to touch the damned thing, it's way outside of my job responsibilities and I won't accept responsibility. So, it's your ball. Wait for the installation electrician or push it yourself and *you* take any resultant heat for hardware failure."
The manager considered, "It'll be two hours before the electrician gets here!" He switched the breaker off, then to on position. The rack lit up.
It took nearly 12 hours and a very upset COMSEC custodian, to restore all services. Each crypto device required rekeying, requiring the presence of said custodian to provide the appropriate USB (and other devices) keys.
Six months before, we had a similar outage, due to a blown transformer and the aforementioned room full of dead batteries. A room that was ignored, right until a US General couldn't use his telephone, due to the outage.
Suddenly, we had the budget to replace that which we had complained of twice weekly.