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Wait for a cool day to install your attic fan. Minimize problems from the insulation by wearing long pants and a long-sleeved shirt. Use eye and breathing protection. Set up a piece of plywood or a wooden tray in the attic as a work area where you can put your tools and parts so you don't lose them in the insulation.
Make the Opening
Remove the gable vent on the side of your house that is opposite your prevailing winds. Center your new fan vent or shutter over the opening, check that it's level, then trace the outline with a pencil. Measure in 5/8 inch from all sides and make a second outline. If you have any 2-by-4 blocking in the way, cut through the nailed ends and remove them, then cut the fan opening along the inner outline. Install the new shutter over the opening and replace the blocking at the bottom of the shutter to help support the fan.
Install the Fan
Cut a piece of plywood wide enough to reach the framing studs on either side of the vent. Use a template if provided or the fan itself to trace the airway circle in the center of the plywood. Cut out the circle. Place the fan over the circle. Look for any "UP" or "DOWN" markings on the fan to orient it correctly, then fasten the fan to the plywood, using the supplied mounting brackets. Pick up the plywood, center the fan over the vent and screw the plywood securely to the attic framing. Rotate the blades to make sure they move freely. Screw the fan thermostat box to the plywood, making sure it is level.
Connect the Power
With power to the circuit disconnected, run the electrical circuit for your fan up to a junction box in the attic. Staple the cable to the framing every 12 inches, if possible. Run cable from the junction box into the thermostat. Secure the cable to the box using an NM connector, and strip the sheath from the part of the cable in the box. Connect the bare ground to the green terminal, then splice the white wires together, followed by the black wires. Cover the splices with wire nuts and tuck the wires into the box. Close the box and set the thermostat to 105 degrees F.