2 15 amp plugs = 1 30 amp plug

I wasn't allowed to take a picture, but I swear it's true.

Walked into a phone room for a place. Snaking across the floor is a power cable to their 3000VA UPS, so L5-30 twist lock plug. That's plugged into a receptacle in an old-work box laying on the floor. Coming out of the old work box is 2 regular computer type power cables, which are both plugged into the same duplex outlet.

In theory, the first time the power gets cut to the building, when it comes on, the UPS will start recharging the batteries plus supplying power to the load, drawing close to the max on the unit, which should be 21 amps or so. I'd guess they've just gotten lucky, or the guy was "smart" enough to replace the breaker on that circuit with a larger one.

Good news is they've already got an electrician scheduled to repair it, I don't know how long it's been like that.