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403.3.1.1.1 Zone outdoor airflow.
The minimum outdoor airflow required to be supplied to each zone shall be determined as a function of occupancy classification and space air distribution effectiveness in accordance with Sections 403.3.1.1.1.1 through 403.3.1.1.1.3.
403.3.1.1.1.1 Breathing zone outdoor airflow.
The outdoor airflow rate required in the breathing zone V
bz
of the occupiable space or spaces in a zone shall be determined in accordance with Equation 4-1.
V
bz
= R
p
P
z
+ R
a
A
z | (Equation 4-1) |
where:
A
z | = | Zone floor area: the net occupiable floor area of the space or spaces in the zone. |
P
z | = | Zone population: the number of people in the space or spaces in the zone. |
R
p | = | People outdoor air rate: the outdoor airflow rate required per person from Table 403.3.1.1. |
R
a | = | Area outdoor air rate: the outdoor airflow rate required per unit area from Table 403.3.1.1. |
403.3.1.1.1.2 Zone air distribution effectiveness.
The zone air distribution effectiveness (E
z
) shall be determined using Table 403.3.1.1.1.2.
Air Distribution Configuration | Ez |
Ceiling or floor supply of cool air | 1.0
e |
Ceiling or floor supply of warm air and floor return | 1.0 |
Ceiling supply of warm air and ceiling return | 0.8
f |
Floor supply of warm air and ceiling return | 0.7 |
Makeup air drawn in on the opposite side of the room from the exhaust and/or return | 0.8 |
Makeup air drawn in near to the exhaust and/or return location | 0.5 |
For SI: 1 foot = 304.8 mm, 1 foot per minute = 0.00506 m/s, °C = ((°F) - 32) /1.8.
a. "Cool air" is air cooler than space temperature.
b. "Warm air" is air warmer than space temperature.
c. "Ceiling" includes any point above the breathing zone.
d. "Floor" includes any point below the breathing zone.
e. Zone air distribution effectiveness of 1.2 shall be permitted for systems with a floor supply of cool air and ceiling return, provided that low-velocity displacement ventilation achieves unidirectional flow and thermal stratification.
f. Zone air distribution effectiveness of 1.0 shall be permitted for systems with a ceiling supply of warm air, provided that supply air temperature is less than 15°F above space temperature and provided that the 150 foot-per-minute supply air jet reaches to within 4 1/2 feet of floor level.
403.3.1.1.1.3 Zone outdoor airflow.
The zone outdoor airflow rate (V
oz
), shall be determined in accordance with Equation 4-2.
V
oz
= V
bz / E
z | (Equation 4-2) |
403.3.1.1.2 System outdoor airflow.
The outdoor air required to be supplied by each ventilation system shall be determined in accordance with Sections 403.3.1.1.2.1 through 403.3.1.1.2.3 as a function of system type and zone outdoor airflow rates.
403.3.1.1.2.1 Single zone systems.
Where one air handler supplies a mixture of outdoor air and recirculated return air to only one zone, the system outdoor air intake flow rate (Vot) shall be determined in accordance with Equation 4-3.
V
ot
= V
oz | (Equation 4-3) |
403.3.1.1.2.2 100-percent outdoor air systems.
Where one air handler supplies only outdoor air to one or more zones, the system outdoor air intake flow rate (Vot) shall be determined using Equation 4-4.
V
ot
=
Σall zones
V
oz | (Equation 4-4) |
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