Labconco Class I Enclosure Models 3980423 - Manual (Page 44)

Chapter 6: Maintaining Your Filtered Enclosure
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Calibrate and Operate the Airflow Monitor
Guardian Airflow Monitor (LED Monitor)
Refer to Figure 6-2 for operation and calibration.
Labconco Airflow Monitor / Airflow Switch Operation
The Guardian Airflow Monitor (LED) consists of a circuit board and an airflow
switch. This switch indicates airflow as safe or low. It does not provide an actual
face velocity, but a small setscrew in the back of the sensor can adjust the airflow
level that it classifies as “good/safe” or “low/alert.”
The circuit board provides power to the sensor and also contains a “safe (green)”
and “alert (red)” airflow LED indicators, as well as a “SILENCE ALARM” button
to quiet the audio alarm. When first powered up, the PCB will light both red and
green LED indicators and sound the alarm to indicate it is working. After 5
seconds, the air monitor will indicate either good or bad airflow based on what the
connected airflow switch detects. For low airflow, the unit will wait for 10
seconds of bad indications before it sounds both the audio alarm and the red “alert”
LED indicator. If the “SILENCE ALARM” button is pressed, the audio alarm will
be silenced, but the red “alert” LED will remain on. The alarm is silenced
indefinitely unless an airflow change is detected. If safe airflow is later detected
for 10 seconds, the green “safe” LED will be lit and the “alert” (red) LED will be
shut off. At any time the airflow is safe/good, one can press the SILENCE
ALARM test button and the audio alarm and the red LED will turn on as long as
this button is held down. The PCB has also a two-pin connector for use as an
external output with isolated relay contacts that close when the red/alert LED is lit
(low airflow). These relay contacts are not affected by the “SILENCE ALARM”
button.
The PCB is mounted behind the front panel using standoffs and an appropriate label
is used to highlight the “SILENCE ALARM” button with clear areas for the red and
green LED’s. No holes to allow sound to be broadcast louder are necessary.
The PCB can be prepared as a factory special with an additional connector for the
following external inputs, and having the following possible functions:

External Alarm allows an external signal to sound the alarm, such as a sash
open switch, or a “fail” signal from the building airflow system.
 Alarm Disable allows an external signal to prevent a “low” airflow alarm from
occurring.
 Night Setback allows an external signal to prevent a “low” airflow alarm from
occurring (not any different from Alarm Disable above other than the
terminology.)

Contact Labconco for ordering information on this special PCB.
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