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How to Install a Solar-Powered Attic Fan

An attic fan can help reduce heat inside a home and overall cooling costs. These step-by-step instructions show how to install a solar-powered fan that's low maintenance.

More in Electrical

installing a solar powered attic fan

Step 1: Choose a Fan

A solar attic fan is well-suited for gable ventilation. The separate units for collection, ventilation and control make the system versatile. The kit includes a 40-watt solar panel, a thermostat/controller and a 12-volt DC powered 11-inch diameter fan. For best results, select a solar panel with double the output required by the fan used.

solar attic fan kit well suited for gable vent

Step 2: Determine the Installation Angle

Attic fans are best placed facing due south.

For our project, we have a flat-pitched roof, so a flush-mount unit is all that's needed. After determining the installation angle, it's time to connect the wiring to the terminal box on the underside of the solar panel. A wiring diagram is usually printed on the underside for easy DIY installation.

wiring diagram is printed on underside of panel

Step 3: Connect the Wires and Tighten the Water-Tight Connector

A water-tight connector is added to the outside of the junction/terminal box to keep moisture away from the wiring that will be added.

Strip the 14-gauge wire and thread it through the junction box opening.

Connect the red (positive) wire to the positive terminal; connect the black (negative) wire to the negative terminal.

Add the water-tight lid to the box and tighten it into place. Tighten the water-tight connector.

Step 4: Locate the Rafters and Drill the Brackets

Use a hammer to locate the rafters. The panel will be held securely to the roof by Z-bracket mounts that will be drilled into the rafters. The Z-brackets will also elevate the panel from the hot roof surface, making it work more efficiently.

Stainless-steel hardware should be used to connect the Z-brackets to the inside edges of the panel.

Add butyl sealant under each Z-bracket (Image 1) before drilling the brackets into the roof (Image 2).

Step 5: Run and Secure the Electrical Cable

Run the electrical cable from the panel along the roofline to the end near the gable vent.

Secure the wire to the roof at 18-inch intervals for safety.

Run the wire through the gable vent.

secure wire to roof

Step 6: Measure and Cut a Brace

With the solar panel in place, the fan is ready to be installed in the attic. Select and mark the location of the fan.

Measure and cut a 2x4 brace. Use a drill and screws to secure the brace within the gable opening.

secure brace in gable opening

Step 7: Connect the Wires

Secure the fan to the brace using wood screws (Image 1) and to the surrounding gable area.

Strip the 14-gauge cable that was fed through the opening and connect it to the fan wires to test. (Remember to connect the positive wires to the positive wires on the fan and negative to negative wires.) If enough power is being generated, the fan should start turning (Image 2). If the wires are connected backward, air will blow into the attic instead of being removed.

Step 8: Add the Temperature Controller

If adding a thermal switch/temperature controller, add a standard plastic electrical box to an area near the fan. After securing it into place, feed the cable into the box (which will house the controller) from the solar panel.

Connect one wire from the controller to the panel wiring, and connect the other wire to the fan wiring (Image 2). Use a wire nut to secure all together.

Secure the temperature controller within the electrical box and set a temperature that will activate the fan.

add temperature controller

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