Application

Application Notes
Dual Duct Sequence Configurations
6
Siemens Industry, Inc.
Application Note
A6V11692042
Smart Infrastructure – Building Products
2019-04-01
Overview
14064
Dual Duct Variable Volume with Dedicated Ventilation Duct, Two Inlet Sensors, DCV and
Hot Water Heat with Supply Temp Control: Template 14064 (on DXR2.x12).
This application modulates the supply air dampers of the dual duct terminal box for cooling,
heating, and ventilation (for demand control ventilation a room air quality sensor is required:
QMX3.P74).
Terminal box airflow is maintained at the larger of ventilation airflow or the heating or cooling
airflows. When in heating, the hot water heating coil is modulated to maintain supply air
temperature setpoint as reset by room temperature demand.
The analog outputs for damper control (1DMPR POS, 2DMPR POS) are modulated by respective
airflow PID controllers. The analog output for the hot water heating coil (HTG V POS) is
modulated by a supply air PID controller.
Each duct can be configured to provide hot, cold (or both) airflow, and the source for ventilation
air can be configured to come from cold duct, hot duct, or both. Additionally, the transition
between heating and cooling is configurable for hot/cold airflow mixing control or snap acting
control. See Dual Duct Configurations for detailed information on these topics.
Plant Diagram
VavSuPos1
VavSuPos2
Variable air volume supply air
damper
AirQualR
Room air quality
(part of ROpUn)
VavSuDiffP1
VavSuDiffP2
Supply air VAV differential
pressure sensor
ROpUn
Room operating unit - QMX3.P74
HclHw
Hot water coil
TR
Room temperature
(part of ROpUn)
TSu
Supply air temperature sensor
(for Cascade Supply Temp
Control)
Description of Functions
Basic Functions
Auxiliary Functions
⚫ Operating modes for room, plant and
devices
⚫ Each VAV duct can provide conditioned
air for cooling or heating; heating
function operates using cascaded supply
temperature control loop
⚫ Ventilation air provided by either or both
ducts
⚫ Mixing control or snap action control,
configurable
⚫ Supply air VAV box, pressure sensor
⚫ Hot water coil
⚫ Supply chain coordination
⚫ Green Leaf function
⚫ Comfort button for occupant override