SWS Detail: 6.0301.1 Fresh Air Intake In Forced Air System
Author: Jesse
Locations shall not be located within 10' of property lines or other buildings.
Intakes can not be located within 10' horizontally from any hazardous or noxious contaminant sources such as combustion appliance vents, driveways, streets, alleys, or parking lots unless they are located 25' vertically above such locations.
Penetration should be at least 18" above grade or higher as necessary to prevent obstruction.
Run in the most direct route to exterior.
Size pipe to the CFM requirements determined from the ASHRAE calculations.
Changes in direction reduces the total CFM potential and pipe size might need to be increased.
Drill/cut into the return of the HVAC system as close to the blower as possible upstream from the filter ensuring the outside air passes through the filter.
Install the damper as close as possible to the exterior penetration and while maintaining access to the damper.
Attach the ducting between the damper and the return air penetration.
Ducting needs to be constructed of a minimum 26 ga.
Seal intake ducting with mastic or foil faced butyl tape.
See Air Seal Duct section in this guide
Wiring is specific to the control that will operate the damper.
Read control installation manual for wiring methods.
Most dampers and controllers use a low-voltage system.
There are many different controllers that are available. Install the one that best fits your system.
Controller needs to ensure operations to ASHRAE 62.2 standard.
Insulate any ducting that is between the exterior penetration and the damper to a minimum R-8.
See Duct Insulation section in this guide.
Install a fixed louvered intake cover that has openings no smaller than 1/4" and no larger than 1/2".
Then Caulk with and exterior grade caulking.
Educate client on when it will allow air into the HVAC system and how it functions.
Conduct a Worst Case draft test to verify Category I, II, and III appliances are venting safely before leaving home for the day.
Testing shall be recorded using the Utah WAP Worst Case Draft Test form.