Whoops, I did it again.

I fried an almost new inverter. A not so cheap Samlex 1500W Pure Sine Wave inverter. Back fed 120VAC into it & BANG! What made me hit that switch when shore power was present? Did the same thing to my boat inverter about 20 years ago. Slow learner.

Where's my sign?

Not being a techy guy, obviously, is it worth getting repaired or should it be used as a boat anchor?