By default, and without intervention; all zones in between the most upstream and most downstream zones always try to convey items downstream if the next downstream zone is clear. To cause an intermediate zone to accumulate based upon a wired signal, you need to utilize the Aux I/O Pin 2 signal for the zone in questions as an Accumulate input.

Assuming the intermediate zone we want to accumulate is the upstream zone and the upstream zone is connected to the Left side of the module; we set the Left Aux I/O Pin 2 to Accumulate from the drop down box and make sure we click the “UP” arrow to indicate that the Left Pin 2 signal is to be associated with the Upstream Zone. When the Left Pin 2 is energized, the upstream zone will accumulate the next item that arrives