Assortment / System Description

Room pressurization and fume hood control
Alarms
21
A6V10866237_en--_b_08 193 | 275
Combination of
DXR2.E17…
DXR2 DXR2
1 Room pressurization Room pressurization
2 Room pressurization Fume hood
3 Room pressurization with thermal
power
Room pressurization with thermal
power
4 Room pressurization with thermal
power
Fume hood
5 Chilled ceiling and/or radiator
application
21.4 Alarms
The controller is equipped with ventilation and pressurization alarms. The
controller’s alarms are designed to:
● Inform building operation personnel that the system is not functioning
correctly.
● Supply data for documenting laboratory safety records through trending.
These alarms can be broadcast across a network.
The ventilation alarm turns on when ventilation does not meet the required
level.
● In a negative pressure room, air flow ventilation equals the total exhaust
flow.
● In a positive pressure room, air flow ventilation equals the total supply flow.
The ventilation alarm does not respond directly to flow rates or flow loop errors
at a particular terminal. It applies to the calculated ventilation rate.
The pressurization alarm turns on when the calculated value of the transfer
flow is too far from the setpoint. The flow tolerance that triggers the transfer
flow alarm is set in physical flow units.
● Disabled: The alarm is not triggered.
● Alarm on high value. The alarm is triggered when the transfer flow is more
than the setpoint plus the tolerance, which means more than the required
amount of air moves into the room.
● Alarm on low value: The alarm is triggered when the transfer flow is less
than the setpoint minus the tolerance, which means less than the required
amount of air moves into the room or the air moves in the wrong direction.
● Alarm on high or low value: The alarm is triggered when the transfer flow is
more than the setpoint plus the tolerance or when the transfer flow is less
than the setpoint minus the tolerance.
The alarm function includes a delay to prevent nuisance alarms / fault alarms.
The air flow transfer alarm can serve many needs. The alarm goes off due to
several conditions: flow loop cannot meet setpoint, flow loop unstable, damper
overridden, actuator disconnected, flow setpoint overridden, flow sensor failed.
With the customer, select a flow level and delay time. The delay time should be
large enough to avoid alarms during normal air flow transients. For example:
ventilation and temperature setpoints change with occupancy and the air flow
setpoint might make a large jump, leading to a brief mismatch between supply
and exhaust.
Ventilation Alarm
Pressurization alarm