C. Negative Pressure
WARNING
Asphyxiation Risk.
•Negative pressure can cause spillage of com- bustion fumes, soot and carbon monoxide.
•Appliance needs to draft properly for safety.
Negative pressure results from the imbalance of air available for the appliance to operate properly. It can be strongest in lower levels of the house.
Causes include:
•Exhaust fans (kitchen, bath, etc.)
•Range hoods
•Combustion air requirements for furnaces, water heaters and other combustion appliances
•Clothes dryers
•Location of
•Imbalances of the HVAC air handling system
•Upper level air leaks such as:
-Recessed lighting
-Attic hatch
-Duct leaks
To minimize the effects of negative air pressure:
•Install the outside air kit with the intake facing prevailing winds during the heating season
•Ensure adequate outdoor air for all combustion appliances and exhaust equipment
•Ensure furnace and air conditioning return vents are not located in the immediate vicinity of the appliance
•Avoid installing the appliance near doors, walkways or small isolated spaces
•Recessed lighting should be a “sealed can” design
•Attic hatches weather stripped or sealed
•Attic mounted duct work and air handler joints and seams taped or sealed
•Basement installations should be avoided
26 | Heatilator • |