Commissioning Instructions

Before You Begin
Configuring Airflow Control — Application 2942
25
Siemens Industry, Inc. Start-up Procedures 140-1321
Restricted 2015-11-04
Mode 2 - Operates with a PID loop, but no Venturi table.
In this mode, the controller operates with PID control based on a flow sensor input, but
the Venturi table is not used. See the
PID Only Mode section for specific information
on this mode.
Mode 3 - Operates with Venturi table, but no PID loop
In this mode, the controller operates open loop (without a flow sensor). There is no PID
control. Positioning of the actuator is based solely on a Venturi table consisting of
command voltages and their resultant corresponding airflows. See the
Open Loop
Operation (Mode 3)
section for specific information on configuring the application for
open loop control.
Before setting up airflow control, you should read and understand the sections on
Venturi Air Valve Calibration and Table Statement Editing in the Application Note
documents;
Fume Hood Controller 2-Position (140-1317), Fume Hood Controller
Application 2941 (140-1319) or Fume Hood Controller Application 2942 (140-1320) this
information is located on Info Link or Asset Portal. This is especially important if you
need to edit the Venturi table statement during start-up.
Calibrating the Venturi Air Valves (Modes 1, 3)
If operating without an Air Velocity Sensor, see the Open Loop Operation (Mode 3)
section.
This step builds a lookup table in the controller that represents actuator signal versus
airflow. If you airflow readings are not steady (± 10%) when you calibrate, it will
probably fail.
 Set CAL EXH VLV to YES. After approximately three minutes, calibration will finish
and the application will automatically set CAL EXH VLV back to NO. If the
calibration was successful, EXH VLV STAT will be set to CAL OK. If it reads
NOTCAL, the calibration was rejected and the valve must be calibrated again.
Check for loose or kinked flow sensor tubes as well as proper actuator and valve
operation, then recalibrate.
NOTE:
The factory default value of EXH VLV STAT is NOTCAL. The value is set whenever a
calibration or table transfer is performed as the last step of the calibration/table
transfer. ("Table transfer" is explained later in the document) EXH VLV STAT is never
used for active control decisions.
Information on how to edit the Venturi table statement is in Venturi Table Evaluation
and Editing
section. After you have manually set the voltage/flow values of the second
supply or exhaust table element equal to the original low flow values, you must then
reset the original low flow point back to these same original values. The end result is
that the first and second table elements (the low flow point and the one immediately
following it) of the affected Venturi Air Valve(s) will have the same voltage and flow
values.
Low Flow Operation - Below 350 fpm (Mode 1)
1. Make sure that both the Air Velocity Sensor is operating normally (EXH AIR VOL
has a status of NORMAL), and that the Air Velocity Sensor has been calibrated.
2. Read the minimum cfm flow values from the room schedule or from the exhaust
Venturi air valve housings. Write down this value.