MACH
®
Gas Fired Boiler
14
Table of Applicable Vent Materials by MACH
®
Boiler Model
Model
AL29-4C 316L SS CPVC
PVC
US C750 – C1050
X
X
X
No
CAN C750 – C1050 X
X
Note 2 No
3.5.2 Combustion Air
Combustion air must be free from dust, lint, etc. The presence of such materials in the air supplied to the burner
could cause nuisance "Low Air" shutdowns or premature burner failure. The boiler should not be operated during
construction while the possibility of drywall dust, demolition dust, etc. exists.
The combustion air supply must be completely free of chemical fumes which may be corrosive when burned in the
boiler. Common chemicals which must be avoided are fluorocarbons and other halogenated compounds, most
commonly present as refrigerants or solvents, such as Freon, trichloroethylene, perchlorethylene, chlorine, etc.
These chemicals, when burned, form acids which quickly attack the boiler and the boiler stack. The result is improper
combustion and premature boiler failure.
Under no circumstances shall the boiler room ever be under a negative
pressure. Particular care should be taken when exhaust fans, compressors, air-handling units or other
equipment may rob air from the boiler. Note that this equipment might be in rooms other than the boiler
room.
3.5.2.1
Air Inlet Requirements – United States (NFPA 54/ANSI Z223.1 & NFPA/ANSI 211)
When air is supplied from inside the building, the total required volume shall be the sum of the required volume for all
the appliances located in the mechanical room. Adjacent rooms furnished with fixed openings communicating directly
with the mechanical room are considered part of the required volume. The minimum volume is 50 ft
3
per 1000 Btu/hr
(4.8 m
3
/kW) of installed appliance input capacity.
Openings used to connect indoor spaces to obtain the required minimum volume shall be sized as follows:
•
When rooms are on the same floor, each opening shall have an area equal to 1 square inch for each 1000 Btu/hr
(2200 mm
2
/ kW) of installed appliance input capacity, but not less than 100 square inches. One opening should
commence less than 12 inches above the floor and the other less than 12 inches below the ceiling. The minimum
dimension of air openings shall be 3 inches.
•
When rooms are on different floors, each opening shall have an area equal to 2 square inches for each 1000
Btu/hr (4400 mm
2
/ kW) of installed appliance input capacity.
When combustion air is supplied from outside the building, the boiler room shall be provided with one or two openings
to ensure adequate combustion air and proper ventilation.
When using one permanent opening, the opening shall commence within 12 inches of the ceiling and shall
communicate directly with the outdoors or through a vertical or horizontal duct that communicates to the outdoors.
•
Minimum free area of the opening is 1 square inch for each 3000 Btu/hr (700 mm
2
/ kW) of installed appliance
input capacity, and
•
Not less than the sum of the areas of all vent connectors in the room.
When using two permanent openings, one opening shall commence within 12 inches above the floor and the other
within 12 inches below the ceiling, preferably on opposite walls. The openings shall communicate directly, or by way
of ducts, with free outdoor air. The minimum net free area of the openings shall be calculated in accordance with the
following:
Note 2: In Canada, any CPVC used for venting must be listed to ULC
S636.
