Not trying to shame you but...50 degrees? Do you live in Phoenix and keep your home at 60 degrees?
So to keep your home at 70, you need exit temperature to be 50-55F.
seems like it might be lower or higher, depending on humidity.
So on a 102 degree day, for 72 degrees indoors, you might need 52 degree vent temperature.
In phoenix - just go to work and come home after dark.