Do fused discos, back fed breakers work both ways? I know power would have to go both ways if they are closed, but will they open on overcurrent or a short on the solar side? Probably a dumb question.Also trying to remember the terminology for a backfed breaker going both ways, thanks. I thought the were called something specific.
They respond to overcurrent no matter which way it is "flowing".
As has already been mentioned some breakers have a definite line and load side because of things like ground fault protection or other accessories, and a fused safety switch would leave the fuseholders hot if you didn't connect the supply to the "line" terminals.
Solar equipment that backfeeds into the utility typically needs to sense incoming utility voltage or it doesn't produce any "output", so those can be used without creating such problems.
If you had a fault on the "solar side" it would still trip the overcurrent device if the fault ends up drawing high level of current through the device, like say you had two conductors fault to one another - because they are connected to the utility supply fault current will flow from utility source through the fuse/breaker to the fault location and back on the other conductor involved.
