Swamp coolers, or evaporative cooling systems, are popular in the western United States where outside air is very dry. These coolers operate by drawing hot outside air across a cooling pad or screen. The dry air picks up moisture; the evaporation of water absorbs heat and cools the incoming air. The cooler air containing higher humidity is blown into the home to cool it. Swamp coolers are optimally sized to provide 20 to 40 air changes per hour.
Calculate the cooler air volume required for your home by multiplying three figures. If your home is 2,000 square feet with eight-foot ceilings and 30 air exchanges are needed per hour, then the cooler must provide 480,000 cubic feet per hour of air. This equals 8,000 cubic feet per minute, which is the required air capacity of the cooler. Local equipment dealers can provide assistance with equipment selection to meet your needs.
Determine a location for the cooler on the roof of your home. Inspect the inside of your roof and locate roof joists. The cooler ductwork needs a clear unobstructed path from the roof to the home ceiling. Avoid existing wiring, light fixtures or other obstructions. Once a location has been determined, mark the inside of the roof centered between two roof joists.
Use the cooler duct and a pencil or marking pen to mark the shape of the duct on the inside of the roof. Keep the duct centered between the roof joists. Cut out the marked duct outline with an electric saw. Use an electric drill and drill bit to drill starter holes at the corners of the marked outline, then use a saw to cut the outline.
Climb onto the roof and determine the location of the cooler mounting brackets or mounting legs using the existing hole you have made and the location of the duct connection on the bottom of the cooler. The cooler must be level for proper operation. The mounting brackets or legs must be adjusted for your roof pitch to make a level mounting surface for the cooler. Use metal bracing across multiple roof joists to distribute the load if the mounting brackets cannot be aligned with the joists below. Screw the metal bracing to the joists, then install the legs or mounting brackets to the metal bracing to support the cooler. Use roof tar or caulk to seal all screw holes.
Mark a location below the cooler on the ceiling of the home between two ceiling joists. Use a string plumb bob if needed to locate a point below the duct entering the attic. Slight variations can be used to avoid obstructions since you will be using a flexible duct, but keep the location close to vertical. Use a drywall saw to make a hole and install the ceiling duct register.
Install the cooler duct, a power wire and a thermostat wire, leaving excess wire to allow a thermostat installation inside the home. Use roof tar or waterproofing membrane to seal all openings. Any screws used to mount brackets to the roof should be coated with tar to prevent water entry. Install a duct transition piece if needed for a round flexible duct. Install a flexible duct from the roof duct to the ceiling register. Secure the flexible duct as specified by the manufacturer, typically with screws and aluminum tape.
Mount the cooler on the mounting brackets or legs and connect it to the cooler duct. Secure it to the duct and the mounting brackets or legs per the manufacturer's instructions. Secure the thermostat wire to the cooler thermostat connections. Install the interior thermostat on an interior wall of the home away from the ceiling duct and connect it to the thermostat wire. Connect the cooler power wire to a home electrical circuit as specified by the cooler manufacturer. Use an electrician for electrical connections if you are unfamiliar with electrical wiring.
Run copper or PVC water piping from your home cold water supply to the cooler on the roof. Use pipe brackets to secure the piping on the wall and roof of the home. Use caulk in a caulking gun to seal all holes where pipe brackets are installed and where piping may enter your home, depending on your water connections. Connect the piping to the cooler using connections specified by the cooler manufacturer. Check with local code authorities for requirements to add a water back-flow preventer to the cooler piping.
Turn on the water supply and inspect all water connections for leaks. Turn on the power to the cooler. Turn the home thermostat to a lower temperature than the interior of the home and confirm the cooler turns on and pushes cooler air into the home. Inspect all duct connections inside the roof and seal air leaks with aluminum tape.