Vent Requirements; Combustion Air Supply, Room Air Dependant Application Only - Viessmann Vitocrossal 200 CM2 Series Installation Instructions Manual

Venting

Vent Requirements

Combustion air supply, room air dependent application only
This boiler requires fresh air for safe operation and
must be installed in a mechanical room where there are
provisions for adequate combustion and ventilation air.
There are provisions available on the Vitocrossal boiler
to interlock it with an external combustion air blower.
Provisions for combustion and ventilation air must be
made in accordance with CAN/CSA-B149.1 or .2 Natural
Gas Installation Codes (latest edition) (for installations in
Canada) or in accordance with sections for Combustion
and Ventilation Air, of the National Fuel Gas Code, ANSI
Z223.1 (latest edition) or applicable provisions of local
codes (for installations in the U.S.A.)
Follow local codes to properly isolate the vent pipe when
passing through floors, ceilings and roof.
Whenever possible, install boiler near an outside wall so
that it is easy to duct fresh air directly to the boiler area.
Refer to national codes for duct sizing. Round ducts may
be used.
The boiler must be vented and supplied with combustion
air and exhaust vents as described in this section. Ensure
the vent and combustion air supply comply with these
instructions. (See also page 29).
WARNING
Failure to provide an adequate supply of fresh
combustion air can cause poisonous flue gases to
enter living space, which can cause severe personal
injury or loss of life.
The boiler location should never be under negative
pressure. Exhaust fans, attic fans, or dryer fans may
cause air to be exhausted at a rate higher than the air
can enter the structure for safe combustion. Corrective
action must be taken to ensure enough air is available.
Never cover the boiler or store debris or other materials
near the boiler, or in any way block the flow of adequate
fresh combustion air to the boiler.
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Vitocrossal 200 CM2 Installation Instructions
If boiler is installed in a confined space (a space with a
volume of less than 50 cubic feet per 1000 Btu/h of gas
input for all fuel burning equipment) or building layout
is unusually tight, adequate air for combustion must be
provided by two openings: one located about 6 in. below
the ceiling, the other about 6 in. above the floor. When
communicating directly with the outside, each opening
must have a minimum free area of one square inch per
2000 Btu/h of gas input. When all combustion air is
provided by openings in doors, etc. to adjoining spaces
having adequate infiltration, each opening must have a
minimum free area of one square inch per 1000 Btu/h
of gas input, but not less than 100 in
You must know the free area of louvers used to cover
up the combustion and ventilation openings in closet
installations. If you do not know the free area, assume
20% for wood louvers and 60-75% free area for metal
louvers. When using louvers, the openings have to be
made larger.
For example, a free 14 in. x 6 in. (356 mm x 152 mm)
opening becomes a 14 in. x 10 in. (356 mm x 254 mm)
opening for a grill containing metal louvers.
CAUTION
Do not store chemicals containing chlorine or other
corrosive materials near the boiler, such as bleach,
cleaning solvents, detergents, acids, hair spray,
spray cans, paint thinners, paint, water softener
salt, perchloroethylene, or carbon tetra chloride.
2
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