Improper wiring can damage controllers.
All i2 and b3 24VAC-powered controllers.
Improper wiring, such as reversing the conductors, may result in damage to one or more controllers.
Each i2/b3 low voltage powered controller must have its own 24 VAC step down or isolation transformer.
X2 of the transformer must be connected to earth ground AND to the terminal marked with the ground symbol on the controller.
X1 of the transformer must be connected to the terminal marked "L" or "24VAC".
Here's an example of the proper wiring - the i2_b3+887+Installation+Instructions.pdf.
LL#15151 shows why the RS485/MSTP will go down if power is wired incorrectly.