Instinct Installation Manual

CHAPTER 2 - COMBUSTION AIR & VENTING
7
BEST PRACTICE
Isolating the combustion appliance room
from the rest of the building and bringing in
uncontaminated outside air for combustion
and ventilation is always preferred.
2.4. Methods of Accessing Combustion Air
Into A Space - Category IV
2.4.1. Indoor Combustion Air
NOTICE
• The methods listed in this chapter for accessing
IndoorCombustionAirassumethattheinfiltration
rate is adequate and not less than .40 ACH.
• For infiltration rates less than .40 ACH,
reference the National Fuel Gas Code (NFPA
54 / ANSI Z223.1) for additional guidance.
• Indoor combustion air vent supply must be
installed with a minimum equivalent vent
length of 10 feet. Refer to Vent Supplement
for further guidance.
Opening Size and Location
Openings used to connect indoor spaces shall be sized and
locat ed in accor dance with the f ollo wing , see F ig .1 b elow :
• Combining spaces on the same story. Each opening
shall hav e a minimum fr ee ar ea of 1 sq . in./1000 Btu/hr
of the total input rating of all gas utilization equipment
in the space , but not less than 100 sq . inches . One
opening shall commence within 12 inches of the t op ,
and one opening shall commence within 12 inches
of the bottom of the enclosure. The minimum dimen-
sion of air openings shall be not less than 3 inches.
2.4.2. Outdoor Combustion Air
Opening Size and Location
The minimum dimension of air openings shall be not
less than 3 inches
Openings used to supply combustion and ventilation
air shall be sized and located in accordance with the
following:
• One Permanent Opening Method . One permanent
opening , commencing within 12 in. of the t op of
the enclosure, shall be provided as shown in Fig.
2 below.
The equipment shall have clearances of
at least 1 inch from the sides and 6 in. from the
front of the appliance. The opening shall directly
communicate with the outdoors or shall commu-
nicate through a vertical or horizontal duct to the
outdoors or spaces that freely communicate with
the outdoors and shall have a minimum free area
of the following:
• 1sq. in./3000 Btu/hr of the total input rating of
all equipment located in the enclosures, and
• Not less than the sum of the areas of all vent
connectors in the space.
• C ombining spac es in di ff er ent stories . T he v olumes
of spaces in different stories shall be considered
as communicating spaces where such spaces are
connected by one or more openings in doors or floors
ha ving a t otal minimum fr ee ar ea of 2 sq . in./1000 Btu/
hr of total input rating of all gas utilization equipment.
Gas Vent
Openings
Io n- ic
186°F
D HW 15
6°F
Targ et = 186°F
DHW De m a n d
Fig. 1 - All Combustion Air from Adjacent Indoor
Spaces through Indoor Combustion Openings
Gas Vent
Opening
Alternate
opening
location
Fig. 2 -All Combustion Air from Outdoors Through
One Permanent Air Opening
Ion-ic
186°F
DHW
156°F
CHAPTER 2