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svf
series
725/850
DIRECT VENT - Room Air Openings (Category IV)
Combustion and Ventilation Air Provision
For direct vent installations, combustion air must be
ducted directly from outside to the boiler air intake
fitting. Sidewall or vertical options are available. The
boiler room will still require air openings for ventilation
and for combustion air for other appliances
Sizing Air Openings
Air openings provide ventilation to prevent
overheating of the boiler controls and boiler space
Use the information in Figure 31, page 46 for air
openings
WARNING
!
Air openings must be sized to handle all
appliances and air movers, such as exhaust fans,
using the air supply. Failure to comply can result
in severe personal injury, death, or substantial
property damage.
The sizing given in Figure 31, page 46 is based
on the National Fuel Gas Code – ANSI Z223 1/NFPA
54, latest edition The sizing allows adequate air
openings for gravity-vented gas appliances (Category
I) when located in the same space as the SVF boiler
When outside air is ducted as directed in this
manual, the SVF commercial boiler is rated as
direct vent (pressurized vent), and has varying
requirements for combustion and ventilation air
The air openings in Figure 31, page 46 will allow
adequate ventilation and combustion air, provided
the boiler room is not subjected to negative pressure
due to exhaust fans or other mechanical ventilation
devices Refer to the National Fuel Gas Code –
ANSI Z223 1/NFPA 54, latest edition, for dealing with
other conditions
Free area and louvers: The free area of openings
means the area after reduction for any installed
louvers or grilles Be sure to consider this reduction
when sizing the air opening
550-100-290/0124
boiler manual
1
Special Considerations
Tight construction
ANSI Z223.1/NFPA 54 defines unusually tight
construction where all of the following is true:
1
Walls and ceilings exposed to the outside
atmosphere have a continuous water vapor
retarder with a rating of 1 perm or less with
openings fitted with gaskets.
2
Weather-stripping has been added on windows
and doors that are capable of being opened
3
Caulking or sealants are applied to areas such as
joints around windows and door frames, between
sole plates and floors, between wall-ceiling
joints, between wall panels, at penetrations for
plumbing, electrical, and gas lines, and in other
openings
For buildings with such construction, provide air
openings into the building from outside Size the
openings per Figure 31, page 46 if appliances are
to use inside air for combustion and ventilation
Exhaust fans and movers
The appliance space must never be under a
negative pressure unless all appliances are installed
as direct vent Always provide air openings sized
to the dimensions required for the firing rate of
all appliances, with the ability to handle the air
movement rate of the exhaust fans or air movers
using air from the building or space
insTallaTion
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