The a/c keeps cutting off before the room gets cold. The fan stays on but now cold air.

A lot of people have only one or two rooms that can take an air conditioner in the window. Often times, the air conditioner is also rated at a cooling power that would make you believe that there is no way that it can to cool the whole house/apartment. You can crank it to the max to try to cool as much as possible, but then this makes one room too cold and the others still stay too hot. You can try blasting the cool air down a hallway with a fan on maximum speed, but that only works so well. And, it's noisy, too. Well, I have two 260 sqr ft rated room air conditioners and I am cooling 2000 sqr feet of house to a comfortable 72 degrees in all rooms and it's been 95 outside all day. How to do it?

The trick is setting up your home to take advantage of laminar air flow. Set your air conditioner to say 68 degrees and start it in the middle of the morning before it feels hot outside. Put the AC deflectors pointing downward and towards the door. Put fans in the doorways pointing out of the rooms that have the AC. Point them level to the floor (not up) and put a fan to one side near the end of long hallways. Set the fans on the lowest power setting (not high). If the hallway branches out into a bigger room, put a fan in the room that is blowing across at a right angle to the entry, pointing the air flow parallel to the wall. This will circulate the cool air around the room. Keep the fans on low and pointed parallel to the floor, not up!

What you have created is a re-circulating air flow system, much like the North Atlantic Current that moderates the temperatures of Europe. You can check this by taking a tissue paper and holding it up to the top of the doorway. The air flow should be pushing the tissue away from the room without the AC and toward the room with the AC. This happens because the warmest air will be toward the ceiling and you want that warm air to make its way across the ceilings and back to the room with the AC, so that it can be cooled again. The cooled air from the AC will sink to the floor and the fans will gently push the air out of the room with the AC. It will stay low and travel along the floor in the opposite direction and into the warmer rooms. If you crank your fans up, you will create turbulent flow and that will not cool your house as efficiently as will laminar flow. Monitor the outside temperature and when it gets cooler outside by a few degrees, turn the AC to fan for about 10 minutes to eek out the last of the cooling. Then open the windows for the night to take advantage of the free cooling that nature provides. That's it! Enjoy the summer!