PREINSTALLATION
where:
Iother = Input of appliances other than fan assisted in Btu/hr
ACH = air change per hour (percent of the volume of the space exchanged per hour, expressed as a decimal)
For fan assisted appliances, calculate the required volume of air using the following equation:
| 15 ft3 | ⎛ | I fan | ⎝ | |
Required Volumefan = |
| ⎜ |
| ⎜ | |
ACH | 1000Btu/hr | ||||
| ⎝ | ||||
|
|
|
| ⎛ |
Ifan = Input of the fan assisted appliances in Btu/hr
Note: These calculations are not to be used for infiltration rates greater than 0.60 ACH.
3.Indoor Air Opening Size and Location: Openings connecting indoor spaces shall be sized and located as follows:
a.Combining spaces on the same floor: Provide two permanent openings communicating with additional spaces that have a minimum free area of 1 in2 per 1000 Btu/hr (22 cm2 per 1000 W) of the total input rating of all gas fired equipment but not less than 100 in2 (645 cm2). One opening is to begin within 12 inches (305 mm) from the top of the space and the other is to begin within 12 inches (305 mm) from the floor. The minimum dimension of either of these openings shall be 3 inches (76 mm). See Figure 1.1 for an illustration of this arrangement.
Figure 1.2: Air Openings – All Air from Indoors on Different Floors
4.Outdoor Combustion Air: Outdoor combustion air is to be provided through one or two permanent openings. The minimum dimension of these air openings is 3 inches (76 mm).
a.Two Permanent Opening Method: Provide two permanent openings. One opening is to begin within 12 inches (305 mm) of the top of the space and the other is to begin within 12 inches (305 mm) of the floor. The openings are to communicate directly or by ducts with the outdoors or with spaces that freely communicate with the outdoors. The size of the openings shall be determined as follows:
i.Where communicating directly or through vertical ducts with the outdoors each opening shall have a minimum free area of 1 in2 per 4000 Btu/hr (22 cm2 per 4000 W) of total input rating for all equipment in the space. See Figure 1.3 for openings directly communicating with the outdoors or Figure 1.4 for openings connected by ducts to the outdoors.
Figure 1.1: Air Openings – All Air from Indoors on the Same Floor
b. Combining spaces on different floors: Provide one or more permanent openings communicating with additional spaces that have a total minimum free area of 2 in2 per 1000 Btu/hr (44 cm2 per 1000 W) of total input rating of all equipment. See Figure 1.2 for an illustration of this arrangement.
Figure 1.3: Air Openings – All Air Directly from
Outdoors
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