In the context of air conditioning systems, the term "grill temperature" might refer to the air temperature at the supply air grille or the return air grille. The supply air grille is where the conditioned air is delivered into the room, while the return air grille is where the air is drawn back into the AC system for cooling.
The ideal temperature for the supply air from the AC system would depend on your personal comfort preferences and the outside weather conditions. Generally, during hot weather, the supply air temperature should be around 15-20°F (8-11°C) cooler than the room temperature. So, if you desire a room temperature of 75°F (24°C), the supply air temperature should be between 55°F to 60°F (13°C to 16°C).
However, it's important to note that there is no fixed "proper" temperature for the supply air grille, as individual preferences can vary. Some people might prefer cooler air, while others might find slightly warmer air more comfortable.
The return air grille temperature would typically be similar to the room temperature since it is pulling air from the room to be cooled by the AC system.
It's worth mentioning that modern split AC systems are equipped with thermostats and automatic temperature control, which can help maintain a comfortable temperature based on your settings. If you have specific concerns about your AC system's performance or temperature settings, it's recommended to consult the user manual or contact a professional HVAC technician to ensure it is functioning optimally and efficiently for your needs.