Intertek ACVC96 Service Instructions Manual page 18

INSTALLATION CONSIDERATIONS
Most homes will require outside air be supplied to the fur-
nace area by means of ventilation grilles or ducts connect-
ing directly to the outdoors or spaces open to the outdoors
such as attics or crawl spaces.
The following information on air for combustion and ventilation
is reproduced from the National Fuel Gas Code NFPA 54/ANSI
Z223.1 Section 9.3.
9.3* Air for Combustion and Ventilation.
9.3.1 General.
9.3.1.1 Air for combustion, ventilation, and dilution of flue gases for
appliances installed in buildings shall be obtained by application of one
of the methods covered in 9.3.2 through 9.3.6. Where the requirements
of 9.3.2 are not met, outdoor air shall be introduced in accordance with
methods covered in 9.3.3 through 9.3.6.
Exception No. 1: This provision shall not apply to direct vent appliances.
9.3.1.2 Appliances of other than natural draft design and other than
Category 1 vented appliances shall be provided with combustion, ven-
tilation, and dilution air in accordance with the appliance manufacturer's
instructions.
9.3.1.3 Appliances shall be located so as not to interfere with proper
circulation of combustion, ventilation, and dilution air.
9.3.1.4 Where used, a draft hood or a barometric draft regulator shall be
installed in the same room or enclosure as the appliance served so as to
prevent any difference in pressure between the hood or regulator and the
combustion air supply.
9.3.1.5 Makeup air requirements for the operation of exhaust fans, kitchen
ventilation systems, clothes dryers, and fireplaces shall be considered in
determining the adequacy of a space to provide combustion air require-
ments.
9.3.2 Indoor Combustion Air. The required volume of indoor air shall
be determined in accordance with the method in 9.3.2.1 or 9.3.2.2 ex-
cept that where the air infiltration rate is known to be less than 0.40
ACH, the method in 9.3.2.2 shall be used. The total required volume
shall be the sum of the required volume calculated for all appliances
located within the space. Rooms communicating directly with the space
in which the appliances are installed through openings not furnished
with doors, and through combustion air openings sized and located in
accordance with 9.3.2.3, are considered a part of the required volume.
9.3.2.1* Standard Method. The minimum required volume shall be 50
3 3
ft per 1,000/Btu/hour (4.8m
9.3.2.2* Known Air Infiltration Rate Method. Where the air infiltra-
tion rate of a structure is known, the minimum required volume shall be
determined as follows:
(1) For appliances other than fan-assisted, calculate using the following
equation:
Required Volume > ________ _________
other
18
/kW).
3
21 ft I
other
( )
ACH 1000 Btu/hr
(2) For fan-assisted appliances, calculate using the following equation:
Required Volume > ________ _________
fan
where:
I = all appliances other than fan-assisted input in Btu per
other
hour
I = fan-assisted appliances input in Btu per hour
fan
ACH = air change per hour (percent of volume of space exchanged
per hour, expressed as a decimal)
(3) For purposes of this calculation, an infiltration rate greater than
0.60 ACH shall not be used in the equations in 9.3.2.2(1) and
9.3.2.2(2).
9.3.2.3 Indoor Opening Size and Location. Openings used to connect
indoor spaces shall be sized and located in accordance with the follow-
ing:
(1)*Combining spaces on the same story. Each opening shall have a
minimum free area of 1 in.
input rating of all appliances in the space but not less than 100 in.
(0.60m 2 ). One opening shall commence within 12 in. (300 mm) of
the top, and one opening shall commence within 12 in. (300 mm) of
the bottom, of the enclosure [see Figure A.9.3.2.3(1)]. The mini-
mum dimension of air openings shall be not less than 3 in. (80 mm).
NOTE: Each opening must have
a free area of not less than one
square inch per 1000 BTU of
the total input rating of all equip-
ment in the enclosure, but not
less than 100 square inches.
Figure A.9.2.3.3.(1) All Combustion Air from Adjacent
Indoor Spaces through Indoor Combustion Air Openings.
(2) Combining spaces in different stories. The volumes 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 having a total minimum free area of 2 in.
2
mm /kW) of total input rating of all appliances.
9.3.3 Outdoor Combustion Air. Outdoor combustion air shall be pro-
vided through opening(s) to the outdoors in accordance with the meth-
ods in 9.3.3.1 or 9.3.3.2. The minimum dimension of air openings shall
not be less than 3 in. (80 mm).
9.3.3.1 Two Permanent Openings Method. Two permanent open-
ings, one commencing within 12 in. (300 mm) of the top and one com-
mencing within 12 in. (300 mm) of the bottom, of the enclosure shall be
provided. The openings shall communicate directly, or by ducts, with
the outdoors or spaces that freely communicate with the outdoors, as
follows:
3
15 ft I
fan
( )
ACH 1000 Btu/hr
2 2
/1000Btu/hr (2200 mm /kW) of the total
Chimney or Gas Vent
Opening
Water
Heater
Furnace
Opening
2
/1000 Btu/hr (4400
2