Application

Sequence of Operation
Operation of AVS FAILMODE
39
Siemens Industry, Inc.
BACnet LCM-OAVS, Application 6760
140-1326
2015-07-07
AVS Failure and AVS FAILMODE Table Values.
AVS FAILMODE
6
Open Supply, Close General Exhaust
7
VENTILATION
8
PRESSURE
AVS FAILMODE values are not additive. For example, if AVS FAILMODE equals
3,
this means to open the supply Damper and hold the general exhaust Venturi Air Valve
if an AVS fails.
The first seven values of AVS FAILMODE (0 through 6) describe specific actions taken
when an AVS fails. For example, if AVS FAILMODE equals
5, then whenever an AVS
fails, the supply Damper will always close and the general exhaust Venturi Air Valve
will always open.
The last two values of AVS FAILMODE do not describe specific actions; that is, when
an AVS fails, the supply and general exhaust will react differently depending on the
circumstances.
If AVS FAILMODE equals
7, the supply Damper will hold. The general exhaust Venturi
Air Valve will also hold if a fume hood is present (that is, if MAX HOOD VOL > 0). If a
fume hood is absent, then the general exhaust Venturi Air Valve will close if the room
is being positively pressurized and open if the room is neutral or negatively pressurized
(that is if VOL DIF STPT is equal to or greater than 0).
If AVS FAILMODE equals
8, the supply Damper will open if the room is being positively
pressurized and close if the room is neutral or negatively pressurized. The general
exhaust Venturi Air Valvewill hold if a fume hood is present. If a fume hood is absent,
the general exhaust Venturi Air Valve will close if the room is being positively
pressurized and open if the room is neutral or negatively pressurized.
NOTE:
If AVS FAILMODE is set greater than 8, it will default to 0.