Obed, I looked at your H&A pad beside your retaining wall and I think it is too close. I don't know anyone who doesn't allow room to get completely around an outside unit. On mine, that's where the service access is. Even if you turn it so the access is on one of the sides not facing the wall, you will need unrestricted airflow for the best heat transfer. I would allow a minimum of 18" behind the unit with 24" being better. I'm not a HVAC expert, but that was my immediate thought when I saw your pad. If I am wrong, surely there are experts here who will correct me.