Application

Sequence of Operation
Open Loop (Mode 3)
26
Siemens Industry, Inc.
BACnet LCM-OAVS, App 2924
140-1304
2015-07-07
Set G OPEN LOOP to YES to indicate that the general exhaust actuator is to operate
open loop. Setting this enable point to
YES will suppress the AVS failure indication that
otherwise would occur when no airflow sensor is connected.
When operating open loop, there is no flow sensor for use in the calibration sequence.
Instead, the Venturi table values are directly input by the user. If the Venturi Valve has
end points for calibration such as 1200 cfm at end voltage, and an implied lower range
of 0 cfm at its other end of the voltage range, you should enter this information into
Point 16, as shown in Example 1 and 2 below.
The direction of actuation, Normally Open or Normally Closed is determined by
VENTRUI ACT.
Point
Flow
Volt
1
0
0.0
2
0
0.0
15
0
0.0
16
1200
10.0
Example 1 - Table with CFM End Limit – direct acting
It may not be necessary to enter 0 values since 0 values are initially in the table by
default when direct acting is selected.
Point
Flow
Volt
1
0
10.0
2
0
10.0
15
0
10.0
16
1200
0.0
Example 2 - Table with CFM End Limits – reverse acting
It may not be necessary to enter 10.0 values since 10.0 values are initially in the table
by default when reverse acting is selected.
If specific information about the voltage at low flow is known, that would be entered into
Point 1 which is reserved for information about low flow. See Examples 3 and 4 below.
Point
Flow
Volt
1
300
3.0
2
0
0.0
15
0
0.0
16
1200
10.0