How to calculate the CFM needed for your attic application.
One square foot of unobstructed inlet area is required for every 300 CFM
Multiply your attic square footage by .7 for minimum air delivery needed to exhaust
the attic. For darker roofs add 15% to the CFM you just calculated. For exceptionally
large attics use two fans that have sufficient exhaust or it will pull the heat
back down into the house.
TO REDUCE THE RISK OF FIRE, ELECTRIC SHOCK, OR INJURY TO PERSONS, OBSERVE THE FOLLOWING:
1. Use this unit only in the manner intended by the manufacturer. If you have questions, contact the manufacturer at the address or telephone number listed in the warranty.
2. Before servicing or cleaning unit, switch power off at service panel and lock the service disconnecting means to prevent power from being switched on accidentally. When the service disconnecting means cannot be locked, securely fasten a prominent warning device, such as a tag, to the service panel.
3. Installation work and electrical wiring must be done by a qualified person(s) in accordance with all applicable codes and standards, including fire-rated construction codes and standards.
4. Sufficient air is needed for proper combustion and exhausting of gases through the flue (chimney) of fuel burning equipment to prevent back drafting. Follow the heating equipment manufacturer's guidelines and safety standards such as those published by the National Fire Protection Association (NFPA), and the American Society for Heating, Refrigeration and Air Conditioning Engineers (ASHRAE), and the local code authorities.
5. When cutting or drilling into wall or ceiling, do not damage electrical wiring and other hidden utilities.
6. The wiring must be permanent. DO NOT USE AN EXTENSION CORD! Use 14 GA. MINIMUM copper wire. Although the Powered Attic Ventilator may be wired directly to power, we advise that some type of shut off switch be installed in the line. Please see the section on electrical wiring for suggested wiring diagrams and instructions.
7. This unit must be grounded.
8. Do not use this unit with any solid state speed control device.
9. For general ventilating use only. Do not use to exhaust hazardous or explosive materials and vapors.
10. To avoid motor bearing damage and noisy and/or unbalanced impellers, keep drywall spray, construction dust, etc. off power unit.
11. This unit has an unguarded impeller. Do not use in locations readily accessible to people or animals.
12. Fan is equipped with a thermostat which may start fan automatically. To reduce risk of injury or electric shock while servicing or cleaning unit, switch power off at service panel and lock service panel to prevent power from being switched on accidentally. When the service disconnecting means cannot be locked, securely fasten a prominent warning device, such as a tag, to the service panel.
13. Home Ventilating Institute (HVI) recommends one square foot of open air inlet per 300 CFM of fan capacity. The best location for these air intake vents are under the eaves with direct access to the attic. Failure to provide these intakes could cause natural-draft gas appliances to back draft.
14. Your attic fan installation will create a screened opening into your attic space. During a heavy rain storm there could be a light spray of rain into this attic space. This is a normal condition with all attic ventilators and will not cause any damage to the structure. We recommend that you do not store any valuable articles directly under the fan opening in the roof. During extreme rain and wind storms you may want to turn on your attic ventilator to prevent excess moisture accumulation in your attic.
15. Records show, under ideal conditions, exposed galvanized steel can remain rust free up to 100 years. For best protection, the exposed portion of the roof sheet should be painted, especially in areas of unusually high industrial air pollution. Follow paint manufacturer's instructions for good adhesion.
16. This ventilator is intended for roof installation. The Broan Model 353 Gable Mount Ventilator is available for side wall applications.
17. The dome may be painted with a high-quality paint. Follow the paint manufacturer's recommendations for PVC plastic or aluminum, as appropriate.