According to the OP, they have the opposite polarity. One runs trains clockwise, the other counterclockwise.
That's true. But there was some question about how he was arranging the polarity. If both loops are wired with the same polarity, do reverse my answers.
Conclusion: #3 is a reversing loop if outer and inner mains tracks are polarised in such a way that left track of outer is connected to left track of inner;
The left rail of the left side of each loop is the same pole? Yes. If these two loops are going to have crossovers between them, the inside rail of each loop needs to be wired together and the outside rails need to be wired together. At that point, any track that can make any clockwise train go counterclockwise (or vice versa) is a reversing loop, and a dead short if not insulated.
But why? In this crude diagram, 3 never has to be created as a reversing loop; just have opposite rail polarities on the inner and outer loops. Since there is only this one connection between the two loops, planning the wiring this way reduces the complications.
He said something about crossovers not shown here. In which case... I think he's getting enough info to figure it out. Even if we aren't.
Post #5: Indeed there are plenty of crossovers between inner and outer mains track. If (as you stated in post #25) "The left rail of the left side of each loop is the same pole.." then a crossover will not need to be isolated. But loop #3 (post #24) will need to be isolated and treated as a reversing section. PS: I had included the full track plan earlier (post #6).
Erik, I am assuming the only connection between the upper and lower levels (a / b of your plans) are the two double tracks in the lower right of your diagrams. Is that correct? Or is there another connection on the left side? Realistically, it doesn't matter, since your three distinct (and easily identifiable) reversing loops can be the only ones on the two levels. Just make sure track polarity follows the rail between levels. There is no need for reversing to be introduced between levels. Direction of travel is 100% immaterial in DCC; only focus on keeping rail polarities consistent.
