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.
Ventilation Alarm
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.
Pressurization alarm
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.