It's worse than that! That's a NEMA L6-20, not a L5-20. That means whatever's on the other end is expecting a 240V, 20A source. And you're providing 120V, 15A.

It's worse than that! That's a NEMA L6-20, not a L5-20. That means whatever's on the other end is expecting a 240V, 20A source. And you're providing 120V, 15A. If you're really lucky, it'll start in "safe mode" with a warning light or message. If you're just lucky, it'll refuse to start at all. If you're unlucky, it'll run but silently limit its capability, so you don't know about your ticking time bomb. And if you're really unlucky, the power supply on the other end is a SMPS which will try to pull down 40 amps.... EDIT: Never mind. The photo appears to be marked L6-20R, but that's an illusion. It's actually shaped, and if you squint marked, to match an L5-20R, which is 125V 20A. Carry on....