Application

Sequence of Operation
Valve Position on Return from Power Failure
36
Siemens Industry, Inc.
Application Note, App 6752
140-1322
2015-07-07
Alarms in Open Loop Mode
When operating a Venturi valve in open loop mode, there is no sensor to measure
actual flow. Instead, flow estimates are based on the current commanded valve
position.
Valve Position on Return from Power Failure
On a return from power failure, the AOs remain OFF for 5 seconds prior to resuming
control. Because of this it is recommended that the Supply Valve be set to Normally
Closed for rooms where negative or neutral pressurization is required and Normally
Opened for positively pressurized rooms. Likewise, it is recommended that the General
Exhaust Valve be set to Normally Opened for rooms where negative or neutral
pressurization is required and Normally Closed for positively pressurized rooms.
Setting of the Venturi direction is via VENTURI ACT.
VENTURI ACT Values.
0
Both Supply and Exhaust Venturi Valves are
Normally Closed (Direct Acting)
1
(default)
Supply Venturi Normally Closed, Exhaust Venturi
Normally Opened
2
Supply Venturi Normally Opened, Exhaust Venturi
Normally Closed
3
Both Supply and Exhaust Venturi Valves are
Normally Opened (Reverse Acting)
Operation of AVS FAILMODE
AVS FAILMODE is an enumerated point that describes how the supply Venturi Air
Valve and the general exhaust Venturi Air Valve will respond if one or both Air Velocity
Sensors (AVS) fail. It can handle both positively pressurized rooms and negatively
pressurized rooms.
The default value of AVS FAILMODE is
0. This default causes both the supply and
general exhaust to hold their current position when an AVS fails. Open Supply, Open
Exhaust and Close Supply, Close Exhaust are not defined AVS FAILMODE states.
AVS Failure and AVS FAILMODE Table Values.
AVS FAILMODE
0
(default)
Hold Supply, Hold General Exhaust
1
Hold Supply, Open General Exhaust
2
Hold Supply, Close General Exhaust
3
Open Supply, Hold General Exhaust
4
Close Supply, Hold General Exhaust
5
Close Supply, Open General Exhaust
6
Open Supply, Close General Exhaust
7
VENTILATION
8
PRESSURE