Application
Sequence of Operation
Ventilation – Constant Volume Mode
15
Siemens Industry, Inc.
Application Note, App 6750
140-1328
2015-07-07
Closing the general exhaust, which lowers airflow and disables cooling completely.
Ventilation – Constant Volume Mode
During Constant Volume (CV) operation, the active supply airflow minimum is used to
ensure that the room always receives enough supply air for proper ventilation. If
necessary, the application raises the general exhaust flow to keep the supply flow from
dropping below the minimum. See
Calculating Exhaust Flow Setpoint
for more
information.
In CV mode the active supply minimum is the setpoint. The active supply airflow
minimum is used to ensure that the room always receives enough supply air for proper
ventilation.
During CV operation, the air volume out of the supply box will equal the active supply
airflow minimum as long as this is sufficient to maintain proper room pressurization.
NOTE:
Regardless of the operation—VAV or CV temperature control—airflow out of both the
supply and general exhaust box will vary as needed in order to maintain proper room
pressurization whenever HOOD VOL changes.
AVS Calibration
Calibration of the air velocity transducer(s) is periodically required to maintain accurate
air velocity readings. Depending on the value of CAL SETUP, calibration takes place
either at fixed time intervals or whenever the application goes into unoccupied mode.
When calibration is in progress, CAL AIR equals YES. After calibration, CAL AIR
returns to NO.
The application uses Autozero Modules connected to AUTOZERO DO8. This means
that the supply and general exhaust flow control devices do not close during calibration
of the transducers.
NOTE:
The LCM does not monitor Fume Hood flow changes for 3 seconds during AVS
calibration.
Venturi Air Valve Calibration (Mode 1, 3)
Calibration of the Venturi Air Valve(s) must be performed at least once during start-up
to determine the relationship between airflow and the voltage curve of the actuator.
WARNING
The LCM cannot calibrate the supply and general exhaust Venturi Valves at the same
time.
They must be calibrated separately.
Prerequisites for calibrating Venturi Air Valves: