Section 3 — Stack and Intake Vent Sizing and Installation
3-16 Part No. 750-363
• Air Velocity: Up to 7 feet = 250 fpm from 3 above.
• Area required: Area = cfm/fpm = 2400/250 = 9.6 square
feet total.
• Area/Opening: 9.6/2 = 4.8 sq-ft/opening (2 required).
Notice
Consult local codes, which may supersede these requirements.
Direct Venting/Sealed Combustion
If combustion air will be drawn directly from the outside by means of
a duct connected to the burner cabinet (Direct Venting) or air intake
(Sealed Combustion), use the following as a guide:
1. Install combustion air vent in accordance with the boiler's
Operating and Maintenance manual.
2. Provide for adequate ventilation of the boiler room or
mechanical equipment room.
3. In extremely cold climates, to mitigate the potential for freezing
and to reduce standby losses, a motorized isolation damper is
necessary to prevent the circulation of cold air through the boiler
during non-operating hours.
4. Refer to Figure 3-3 for suggested piping of direct vent/sealed
combustion installations. Figure 3-8 shows the optional kit
providing easy adaptation of the contractor supplied air duct to
boiler connection. Table 3-2 shows vent sizing information.
Figure 3-8. Optional Direct Vent/Sealed Combustion Kit
!
Caution
Combustion air ductwork should
be securely attached to the boiler
casing. No weight should be sup-
ported by the venturi. Venting
should be installed to allow easy
disconnection for burner service.
For best results, the Cleaver-
Brooks direct vent/sealed combus-
tion kit is recommended. See Table
6-2 for kit part numbers.
For Direct Vent use, omit the flexible
duct connector and air intake collar.
For Sealed Combustion, assemble all
components as shown.
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