Demand controlled ventilation for multiple zone HVAC systems: CO2-based dynamic reset (RP 1547)

Abstract

Demand controlled ventilation (DCV) is used to reduce the system outdoor airflow (OA) when the occupancy of the system is under design occupancy. However, the new versions of ASHRAE Standard 62.1-2010 make DCV more difficult to implement for multiple zone HVAC systems. This article proposes a CO2-based and occupancy-sensor-based dynamic reset of OA rate for multiple zone HVAC systems (“CO2-based DR”). This control strategy uses bioeffluent load estimation with a steady-state assumption to calculate and dynamically reset the system OA rate minimum set-point by solving the multiple-zone system equations for current conditions. Building energy and airflow simulations were implemented to assess the energy performance and indoor air quality of this control strategy. The simulation results showed that the average annual system OA rate for CO2-based DR is 14.6% less than the OA rate for without DCV, in which case the system OA is always maintained as constant. The annual monetary saving as a percentage of the baseline case (without DCV) is between 0.3% and 11.0% for 16 climate zones in the United States.