The answer to 'what size ceiling fan installation do I need' is that the size of ceiling fan you need depends on the size of the room. As a general rule, you'll want a 36-inch ceiling fan for rooms up to 100 square feet, a 42-inch fan for rooms 100-200 square feet, and a 52-inch fan for rooms 200-400 square feet. Larger rooms may require an even bigger fan. It's important to measure your room and choose a fan that's appropriately sized to provide good airflow and cooling.
When installing a ceiling fan, you'll also need to consider the ceiling height. Most standard ceiling fans require at least 8-10 feet of clearance from the floor to the fan blades. If your ceilings are lower, you may need a low-profile or flush-mount ceiling fan model.