Application

Application Notes
Sequence of Operation – Summary
25
Siemens Industry, Inc.
Application Note
A6V11692042
Smart Infrastructure – Building Products
2019-04-01
Sequence of Operation – Summary
Overview
The 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.
PID controllers are provided for each of the following control elements:
⚫ Room heating demand
⚫ Room cooling demand
⚫ Supply air temperature reset for heating coil
⚫ VAV duct 1 airflow setpoint
⚫ VAV duct 2 airflow setpoint
⚫ Ventilation demand
(basic ventilation and/or demand control)
Inputs
⚫ Room temperature sensor
⚫ Room temperature setpoint shift
⚫ Temporary Comfort button
⚫ GreenLeaf button
⚫ Differential pressure sensor, Duct 1
⚫ Differential pressure sensor, Duct 2
⚫ Supply air temperature sensor
Outputs
⚫ Supply damper actuator, duct 1
⚫ Supply damper actuator, duct 2
⚫ Hot water coil modulating valve
Room operating modes
The operating mode of the controlled space is applied according to schedule or
room occupant input. The room operating modes are:
⚫ Comfort (occupied)
⚫ Pre-Comfort (standby)
⚫ Economy (unoccupied)
⚫ Protection (e.g. extended holiday)