RMAN archive log backup with Dual archive destination

We have setup dual archive destinations in our DB environment for redundancy. We want RMAN to pick up the logs only from the primary arch destination and send it to Netbackup and then to tape and then delete from the primary location. We would like to keep the archive logs in the secondary location intact. For some reason, RMAN run block randomly picks up from primary and secondary locations and deletes them accordingly. Is there a configuration or parameter that will force RMAN to look only at the primary arch destination and ignore the secondary destination?
The following is the RMAN run block we use in the archive backup script.