Application

Application Notes
Dual Duct Sequence Configurations
20
Siemens Industry, Inc.
Application Note
A6V11692053
Smart Infrastructure – Building Products
2019-04-01
In use case 4, all ventilation is handled in Duct 2 by dedicated outside air system (DOAS). Minimum ventilation
levels can be specified per room occupancy mode. When configured for DCV (demand control ventilation) an
increase in ventilation flow is provided in response to room IAQ (CO
2
) setpoints configured per occupancy
mode.
Temperature control is provided by Duct 1 and may include optional heating or cooling coils. On an increase in
cooling load, Duct 1 will modulate from cooling flow min to cooling flow max. In heating mode, Duct 1 will pro-
vide air flow to support heating coil(s) from heating flow min to heating flow max.
Use Case 5: Constant volume DD option with ventilation in both ducts,
with mixing control
In use case 5 configurations, the mechanical equipment consists typically of a single fan AHU with separate
elements for heating and cooling air distribution. The hot and cold air streams are drawn from the same
source(s) and driven by the same fan. Outside air ventilation is provided using both ducts.
To achieve the constant volume option, the minimum ventilation parameter(s) located in the room AF for venti-
lation control (VavVntCtl) are set equal or greater than the heating / cooling maximum flow setpoints
(VavSuAirFlMaxC, VavSuAirFlMaxH). When this is done, the terminal provides constant air flow in the Comfort
mode, and may be configured to reduce flow in other room operating modes.
In constant volume configurations, temperature control is maintained at a single setpoint, either heating or
cooling, depending on the setting of parameter VntSprtDdband (Ventilation support in deadband). See follow-
ing examples.