ASHRAE-90.1-2022- - Page 387
Extracted Content
Table L4.2.3-2 DCV Outdoor Air Reduction Curve Coefficients
| Equation Term | DCV OA Reduction (y) as a Function of DCV Effective Controlled Floor Area (x) | Col3 | Col4 | Col5 |
|---|---|---|---|---|
| Equation Term | Office | School | Hotel, Motel, Multifamily, Dormitory | Retail |
| b | 0 | 0 | 0 | 0 |
| x | 0.4053 | 0.2676 | 0.5882 | 0.4623 |
| _x_2 | –0.8489 | 0.7753 | –1.0712 | –0.848 |
| _x_3 | 1.0092 | –1.5165 | 1.3565 | 1.1925 |
| _x_4 | –0.4168 | 0.7136 | –0.6379 | –0.5895 |
Figure L4.2.3-2 DCV OA reduction as a function of controlled floor area.
e. Part-load variable-speed fan and pump power shall be calculated using a cubic function with coefficients
as shown in Table L4.2.3-1. The independent variable shall be the fraction of design water flow rate for pumps and the fraction of design airflow rate for fans as shown in Figure L4.2.3-1. f. Demand control ventilation shall be modeled using a simplified approach that adjusts the design outdoor supply airflow rate based on the area of the building that is covered by DCV with coefficients as shown in Table L4.2.3-2. The input shall accommodate two types of DCV :
- Variable control based on people sensor response (CO2 sensor or other)
- ON/OFF occupied standby control that closes the VAV box primary air damper or shuts off outdoor air when the zone is completely unoccupied based on an occupancy sensor (See Section 6.5.3.8.) (Informative Note: Due to lower probability occurrence, the ON/OFF controls are given 1/3 the reduction of the CO2 sensor DCV . The outdoor air reduction factor shall be based on a smaller area of control being applied to higher density spaces first, adjusted for building type, with outdoor air reduction factors and an application formula as shown.)
For office, school, and retail:
DCV Effective Controlled Floor Area = Area VarDCV + 1/3 × Area ON-OFF AND Area ON-OFF < 1 – Area VarDCV For hotel, motel, dormitory, and multifamily:
DCV Effective Controlled Floor Area = Area VarDCV + Area ON-OFF where
ANSI/ASHRAE/IES Standard 90.1-2022 (I-P) 385
