A ceiling fan with a minimum blade span of 56 inches and a CFM rating of 5500 or higher is sufficient for a 23' x 17' room (or 390 square feet). However, if you want to install two ceiling fans, we recommend choosing two fans designed for half of the room size.ey Ann! a 52 ceiling fan should be fine for that size room, but we wouldn't suggest going much bigger than that since the recommended size ceiling fan for that size room is 50 inches. If you have any other questions, please contact our sales department at sales@delmarfans.com.