Just for reference, here is how the TAIXI 160A MCCB looks inside:
I also bought 2 x 125A (for batteries) and one 160A as a main switch from busbars to 24v inverter.
I was in the same situation as you guys: Couldn't be 100% sure that these are bidirectional (or at least non-polarized) . So I ended up getting 2 x 125A ZJBENY and one 160A Suntree (from Renogy store), as both mention specifically that they are non-polarized. The illustration on the ZJBENY is confusing though...
Anyways, as for the TAIXI: I didn't find any magnets inside, which would be a good sign for non-polarized. Polarized MCBs usually have a magnet to pull the arc into the arc chute. But they are only useful for current flowing in a specific direction. I guess if the current is flowing in the opposite direction intended, the magnet does the opposite: it pushes the arc into the internal components if the MCB , which will probably destroy it or cause a fire.
I have read that manufacturers suggest/require that the "line" (supply) be on the non-moving side of the MCB. As you can see on the TAIXI, the non-moving contacts are connected to top terminals.
I'm not really sure why that requirement exists really...
As far as I could tell (without doing a complete teardown of the TAIXI), both sides look pretty much identical to me.
Except for the fact that the switch is on the left, but it open both sides.
One important thing to note:
It seems that if you press the "test" button it sometimes opens just one side. You should fully turn off and on to get things synced again. I've read this somewhere else too...
Just another thing: Although the 160A is bigger than the 125A, and looks massive, the 160A Suntree/Renogy MCCB is simply huge! I was expecting it to be around the same size as the TAIXI 160A, but it's even bigger!
I don't have a picture of it on hand, but I'll take a photo of mine for you to see the difference. Kinda gives you more confidence in the (expensive) product (also made in China...).