We have a 3KVA uninterruptible power supply that keeps my server rack running. It was working fine before we moved, running off a dedicated NEMA L5-30 outlet connected to a 30A breaker that I'd wired into the breaker panel. Yesterday, I finally got around to wiring in a similar 30A dedicated UPS outlet here, checked with a meter to make certain I had correct voltage and polarity, and plugged the UPS into it to charge.
The UPS powered on with a rather disconcerting bang, charged apparently normally for a while, then shut itself down complaining of unbalanced load. It has subsequently refused to pass its power-on self-test, complaining about the same unbalanced load, whether there is a load connected to its outputs or not.
It goes without saying that this is most annoying. While we do technically have the money to replace it with a reconditioned UPS (about $550) or have this one reconditioned ($430), I'd really rather keep that money in the bank in case we need it for a real emergency or for, say, heat.