Some rooms are simply too large for a single ceiling fan, or the ceilings are so high that it makes more sense to use 2 fans instead of one. In general, rooms that are larger than 20' x 15' will be better served by 2 moderate size ceiling fans rather than 1 large fan. Rooms that are a bit smaller but have much higher ceilings can also use 2 fans for better circulation. So if you want to install 2 fans in the same room, it is important to know how to space them out properly for optimal performance.
To illustrate how to position 2 ceiling fans in a room, we are going to use a room size from someone who most recently asked us how to do this. The room was 17 feet x 15 feet with 17 foot high ceilings.
The goal is to postion the fans equidistantly in the room. The end result with be that the space in the center between the 2 fans is twice the distance that the fans are from the walls. This is accomplished by dividing the width of the room by 4 and centering each fan that same distance from the side walls.
In our example room that is 17 feet wide (which is 204"), 1/4 of that distance is 51". So each fan should be installed with the junction box positioned 51" from the shorter wall. Although the measurment is now shown in the illustration below, you would also position the fans in the middle of the shorter 15 foot wall, which would be 7 1/2 feet from either side.
You can check this calculation using this method: Subtract the combined width of the 2 fans (104") from the width of the longest wall (204"), which in your case leaves 100" of space not occupied by the fans. Divide 100 by 4 to find out how far from each wall the blades will be (25"). Then divide the span of the fan by 2 to find the radius or center location of the fan (26"). Then, add the distance from the wall to the radius of the fan to locate the distance from the wall to position the fan mounting hardware on your ceiling. In this case that is 51" (25" plus 26"). This will leave 25" from each wall to the blades and 50" between the blades of each fan as shown above.