Can a window airconditioner be installed in a fireplace I'd build a simulated window. My apartment doesn't have a convenient window.?

Answer 1

Question: "Can a window air conditioner be installed in a fireplace? I'd build a simulated window. My apartment doesn't have a convenient window." I did this many years ago in a region where temps in the summer routinely reach over 100 degrees F. Having once been an engineer, I analyzed the problem and solution as follows: 1. I did not want an unsecured access to the outside of the house (a window-mounted A/C unit), because of deteriorating social conditions in the area (I have since sold the house --- after removing the fireplace A/C, as it was not "common"). 2. All common window A/C units use no "makeup" air --- that is, no air is brought in from the outside at the A/C unit. The air inside the house is just recirculated, and depends on door and window "leaks" to provide some fresh air. Further, most window A/C units use no active air movement past the exterior heat exchange coils to take away the heat which has been removed from the inside of the house. They depend on wind and convection to take away the heat --- with variable results, as you probably have heard of units shutting down from overheating -- that is, not getting rid of the heat to the outside fast enough. 3. The chimney for a fireplace is a narrow access to the outside --- just like a visionless window. If necessary, the chimney can be "temporarily" divided into two vertical columns --- one supply, one exhaust --- extending down to the back ("outside" section) of the A/C unit when it is placed in the fireplace. MAKE SURE THE DAMPER TO THE FIREPLACE/CHIMNEY IS FULLY OPENED ! It helps to have the chimney cleaned (swept) first, also. 4. Now, the keypiece: The placement of the A/C unit REQUIRES air movement past the back of the unit to take away the heat. The heat WILL build up in the fireplace and chimney to trigger the overheating and shutoff of the A/C unit ---- VERY quickly ! The answer: A. If you are lucky enough to have an "ashcatcher" in the floor of the fireplace which leads to the outside of the house (which is what I had), a properly-sized fan in the top of the chimney will draw outside air INTO the ash-removal opening, PAST the back of the A/C unit inside the fireplace, up the chimney, and vent the hot exchanged air into the atmosphere. B. If you have no ashcatcher, you will need to use a simple chimney divider (made of sheet metal for safety) lowered into the chimney, and put a properly-sized fan into the top of the EXHAUST side (the downwind side of the prevailing hot-weather winds) of the divided chimney. Try to divide the chimney across its narrowest horizontal dimension for simplicity. C. By always putting the fan at the exit point of the exhaust duct, you reduce the amount of air leaking into the house from the heat-removal air pathway, since it more approximates a negative-pressure side on the A/C unit (most window installations can have wind-driven dust coming in at the unsealed margins around the unit). D. How to power the exhaust fan at the top of the chimney? I measured the opening of the chimney and shopped around until I found a cake tin which would fill the chimney opening completely with a lip to hold it onto the top of the brickwork by gravity, cut a fan (exhaust air) hole in it with tin snips, and mounted the fan in it. Then I threaded the fan power cord through a SMALL slot I cut in the outer edge of the cake tin near the brickwork (it's always good to put a rubber wear grommet around the slot to prevent vibration wear on the cord), and just plugged the fan power cord into an extension cord which reached down the chimney, out the fireplace face, and over to the closest outlet (with some slack). I then plugged a properly-rated, outlet plug-in switch into the outlet, and plugged the extension cord into the switch. The A/C unit is usually plugged into the same outlet, but you may have to plug into a circuit which has ONLY the A/C unit on it, as the units draw a LOT of amps ! E. The "properly-sized fan" (cubic feet per minute) is the trickiest part of the whole operation. If you have a chemical engineer friend, he or she can do the sizing calcs for you with just a few operational assumptions, such as heat load, heat transfer efficiencies, ambient air characteristics, etc. If you can't find a chemical engineer, you can try various fan sizes from industrial suppliers like Grainger's, etc, until you find one which works without having the A/C unit shut down because of overheating. You may be able to find the necessary algorithms in chemical engineering or mechanical (HVAC) engineering texts. F. Proper operation of the system: 1. Turn on chimney fan at outlet to establish airflow; then turn on A/C unit. 2. Turn off A/C unit; wait 10 minutes; then turn off chimney fan. 5. Details: A. Mounting the A/C unit on the fireplace floor is usually easy and straightforward, but you may have to put a block under the back end of the unit to make sure it is level enough to work properly --- be sure to read the manufacturer's requirements and instructions; B. Use a screen on the outside intake if you use an ashcatcher --- to keep out the "critters" from outside; no filter is required, as no significant amount of air should enter into the house past the A/C unit from this installation; C. Use flexible foam to form a seal around the A/C unit and the fireplace opening. D. If you wish to push the cold air coming out of the A/C unit inside the house into the ductwork system for distribution around the rooms of the house, I do NOT recommend it because of: the need for you to close off the heating duct at the furnace to prevent loss of cold air from the furnace fresh air intake; because of the need for a fan and ductwork at the A/C unit to the nearest register; and because most window-based A/C units do not have the capacity to cool a large space...... E. Be advised that the popular "roll-around, portable" A/C units for sale usually waste some of the newly-cooled air to push the waste hot air out a window, unsealed fireplace opening, etc. 6. Enjoy! (and take it with you to your next apartment!)