Combustion Air / Boiler Room Ventilation Requirements; Air Supply - Unconfined Spaces - CleaverBrooks CFC-500 Operation, Service And Parts Manual

Section 3 — Stack and Intake Vent Sizing and Installation
3-14
H. COMBUSTI0N AIR/BOILER ROOM VENTILATION
REQUIREMENTS
The boiler(s) must be supplied with adequate quantities of
uncontaminated air to support proper combustion and equipment
ventilation. Air shall be free of chlorides, halogens, fluorocarbons,
construction dust or other contaminants that are detrimental to the
burner/boiler. If these contaminants are present, we recommend the
use of direct vent combustion provided the outside air source is
uncontaminated.
Combustion air can be supplied by means of conventional venting,
where combustion air is drawn from the area immediately
surrounding the boiler (boiler room must be positive pressure), or
with direct vent (direct vent combustion) where air is drawn directly
from the outside. All installations must comply with local Codes and
with NFPA 54 (the National Fuel Gas Code - NFGC) for the U.S. and
for Canada, CAN/CGA B 149.1 and B 149.2.
Note: A boiler room exhaust fan is not recommended as this type of device can
cause a negative pressure in the boiler room if using a conventional air intake.
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).
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.
Part No. 750-263