Cleaver-Brooks ClearFire CFLC-5000 - Air Supply - Unconfined Spaces

Section 3 — Stack and Intake Vent Sizing and Installation
Part No. 750-363 3-11
“Sealed combustion” is a special air ducting method that implies a
gas-tight ducted connection to the burner’s air intake. Contact your
Cleaver-Brooks authorized representative to determine if direct vent
or sealed combustion is appropriate for the installation.
C-B provides optional Combustion Air Adapter kits which can be
used in either Direct Vent or Sealed Combustion configurations.
In accordance with NFPA54, the required volume of indoor air shall
be determined in accordance with the “Standard Method” or
“Known Air Infiltration Rate” Method. Where the air infiltration rate
is known to be less than 0.40 Air Changes per Hour, the Known Air
Infiltration Rate Method shall be used (see Section 8.3 in the
NFPA54 Handbook for additional information).
3.5.1 Air Supply - Unconfined Spaces (For U.S. Installations
Only)
A. All Air From Inside the Building - If all combustion air is
drawn from inside the building (the mechanical equipment
room does not receive air from outside via louvers or vent
openings and the boiler is not equipped with direct vent
combustion) and the boiler is located in an unconfined
space, use the following guidelines:
1. The mechanical equipment room must be provided with
two permanent openings linked directly with additional
room (s) of sufficient volume so that the combined
volume of all spaces meet the criteria for an unconfined
space. Note: An "unconfined space" is defined as a space
whose volume is more than 50 cubic feet per 1,000 Btu
per hour of aggregate input rating of all appliances
installed in that space.
2. Each opening must have a minimum free area of one
square inch per 1,000 Btu per hour of the total input
rating of all gas utilizing equipment in the mechanical
room.
3. One opening must terminate within twelve inches of the
top, and one opening must terminate within twelve
inches of the bottom of the room.
4. Refer to the NFGC, Section 8.3 for additional
information.
B. All Air From Outdoors - If all combustion air will be received from outside the building (the
mechanical room equipment is linked with the outdoors), the following methods can be used:
1. Two Opening Method - The mechanical equipment room
must be provided with two permanent openings, one
terminating within twelve inches from the top, and one
opening terminating within twelve inches of the bottom of
the room.