I am taking rman full backup every night.
Retention Policy is configured to redundancy 1.
I want to delete backup sets everyday.This can be done 
If I give command delete obsolete in RMAN script.
Right now I am  using following command for archivelog backup:-
backup archivelog all not backed up 1 times;
delete noprompt archivelog all completed before 'sysdate-3' 
 backed up 1 times to device type disk;
With delete obsolete archivelogs backup will never be deleted
with redundancy 1.
I want RMAN to delete archivelogs backups after 7 days from 
the disk to save the disk space.
Please suggest me how can I acheive this.

delete noprompt backup of archivelog until time 'sysdate-7';