International comfort products H8UH5050B12C2 Installation Instructions Manual page 9

Indoor Combustion Air
Standard and Known- Air- Infiltration Rate Methods
© NFPA & AGA
Indoor air is permitted for combustion and ventilation, if the
Standard or Known- -Air- -Infiltration Rate Method is used.
!
CARBON MONOXIDE POISONING HAZARD.
Failure to supply adequate combustion air could
result in personal injury or death.
Most homes will require additional air from
outdoors for combustion and ventilation. A space
with at least 50 cubic feet per 1,000 BTUH input
rating or homes with tight construction may need
outdoor air, supplied through ducts, to supplement
air infiltration for proper combustion and
ventilation of flue gases.
MINIMUM SPACE VOLUME FOR 100% COMBUSTION AND VENTILATION AIR FROM INDOORS (ft
Table 2
Other Than Fan- Assisted Total
ACH 30
0.60 1,050
0.50 1,260
0.40 1,575
0.30 2,100
0.20 3,150
0.10 6,300
0.00 NP
NP = Not Permitted
Table 2 Minimum Space Volumes were determined by using the
following equations from the National Fuel Gas Code ANSI
Z223.1/NFPA 54- -2006, 9.3.2.2:
1. For other than fan- -assisted appliances such as a draft
hood--equipped water heater,
3
21 ft
Volume
=
other
ACH
2. For fan- -assisted appliances such as this furnace,
3
15 ft
Volume
=
fan
ACH
If:
= combined input of all other than fan- -assisted
I
other
appliances in Btu/hr
= combined input of all fan- -assisted appliances in Btu/hr
I
fan
ACH = air changes per hour (ACH shall not exceed 0.60.)
The following requirements apply to the Standard Method and to
the Known Air Infiltration Rate Method.
• Adjoining rooms can be considered part of a space, if there are
no closable doors between rooms.
• An attic or crawl space may be considered a space that freely
communicates with the outdoors provided there are adequate
441 01 5003 01
(1,000's Btuh)
40 50
1,400 1,750
1,680 2,100
2,100 2,625
2,800 3,500
4,200 5,250
8,400 10,500
NP NP
(
)
I
other
1000 Btu / hr
(
)
I
fan
1000 Btu / hr
Specifications are subject to change without notice
The Standard Method may be used, if the space has no less
volume than 50 cubic feet per 1,000 BTUH of the maximum input
ratings for all gas appliances installed in the space. The standard
method permits indoor air to be used for combustion and ventilation
air.
The Known Air Infiltration Rate Method shall be used if the
infiltration rate is known to be less than 0.40 air changes per hour
(ACH) and equal to or greater than 0.10 ACH. Infiltration rates
greater than 0.60 ACH shall not be used. The minimum required
volume of the space varies with the number of ACH and shall be
determined per Table 2 or Equations 1 and 2. Determine the
minimum required volume for each appliance in the space, and add
the volumes together to get the total minimum required volume for
the space.
Fan- assisted Total
(1,000's Btuh)
50 75
1,250 1,875
1,500 2,250
1,875 2,813
2,500 3,750
3,750 5,625
7,500 11,250
NP NP
ventilation openings directly to outdoors. Openings MUST
remain open and NOT have any means of being closed off.
Ventilation openings to outdoors MUST be at least 1 square
inch of free area per 4,000 BTUH of total input rating for all gas
appliances in the space.
In spaces that use the Indoor Combustion Air Method,
•
infiltration should be adequate to provide air for combustion,
ventilation and dilution of flue gases. However, in buildings with
unusually tight construction, additional air MUST be provided
using the methods described in section titled Outdoor
Combustion Air Method:
Unusually tight construction is defined as
•
Construction with:
1. Walls and ceilings exposed to the outdoors have a
continuous, sealed vapor barrier. Openings are gasketed or
sealed and
2. Doors and openable windows are weather stripped and
3. Other openings are caulked or sealed. These include joints
around window and door frames, between sole plates and
floors, between wall--ceiling joints, between wall panels, at
penetrations for plumbing, electrical and gas lines, etc.
Ventilation Air
Some provincial codes and local municipalities require ventilation
or make--up air be brought into the conditioned space as
replacement air. Whichever method is used, the mixed return air
temperature across the heat exchanger MUST not fall below 60° F
so that flue gases will not condense excessively in the heat
exchanger. Excessive condensation will shorten the life of the heat
exchanger and possibly void your warranty.
3
)
100 125
2,500 3,125
3,000 3,750
3,750 4,688
5,000 6,250
7,500 9,375
15,000 18,750
NP NP
150
3,750
4,500
5,625
7,500
11,250
22,500
NP
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