Warning
In areas of high snowfall, users must be advised to check side wall vent and air
intake terminations on a regular basis to ensure blockage does not occur.
3.5.8 Direct vent combustion air intake piping
The direct vent option uses piping from the outside to supply combustion air directly to the
boiler’s combustion air connection. Combustion air piping - if used - is inserted directly into the 4"
PVC-sized fitting, and increased immediately to 6".
At a new construction site, or during renovations, action must be taken to protect the boiler from
drywall dust or other construction related contaminants; combustion air should be drawn from a
clean source (e.g. outdoors) and the boiler should be isolated from interior dust sources. Do not
seal boiler case openings directly when firing.
Known Corrosive Contaminants to Avoid
Cements and glues Refrigerant leaks from cracks in coils
Paint or varnish removers Sodium chloride or potassium chloride used for
water softening
Adhesives used to fasten building
products and other similar products
Chemicals in perming solutions
Chlorinated waxes or cleaners Chlorofluorocarbon chemicals found in spray cans
Chlorine-based swimming pool chemicals Antistatic dryer sheets in clothes dryers
Hydrochloric acid or muriatic acid used in
household cleaning and stain removal
Chlorine-type bleaches, detergents, and cleaning
solvents found in household laundry rooms
Calcium chloride used for snow and ice
clearing
Warnings
In addition to preventing ingestion of chemical contaminants, ensure air
intake terminals are not installed in locations where contamination might
occur due to ingestion of particulate foreign material (dust, dirt and debris).
Configure intake air openings, so that rain or other forms of moisture cannot
enter the air intake piping system. Otherwise serious damage to the boiler
may result.
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