Chapter 6: Maintaining Your Enclosure
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Guardian 500 Calibration Procedure
Each alarm module and enclosure/fume hood is unique and needs to be individually
calibrated in the field. The procedure for the adjustment is as follows:
1.
Double check the installation to make sure that monitor and power supply are
properly installed.
2.
Allow 10 minutes for the monitor to warm up once power has been connected.
3.
Determine the low flow set point for your monitor. This is the value where the
monitor will first indicate a low flow condition. The red light will be on for this
value. Refer to your industrial hygiene officer for the proper low flow set point or
consult the table below.
4.
Adjust your enclosure/fume hood airflow to the low flow set point as previously
determined. The exhaust flow can be lowered by adjusting the speed control on the
FilterMate or by using an adjustable damper on the exhaust blower. Typical alarm
conditions are set at face velocities of 10 to 20 feet per minute below the normal
operating conditions due to supply air and exhaust air fluctuations, as well as room
air cross drafts. See note 8 if the low airflow volume or sash opening cannot be
adjusted.
5.
Using a properly calibrated thermoanemometer, determine the velocity through the
face of the enclosure by taking a detailed velocity traverse. Divide the face area
into equal increments. One reading per square foot of face area is normally
recommended for an accurate traverse. Compute the average velocity for this area.
6.
If the red light alarm is on, slowly turn the adjustment screw counterclockwise until
the green light is activated. If the green light is on, slowly turn the adjustment
screw clockwise until the red light comes on. Slowly turn the adjustment screw
back until the red light is activated. It is important that these adjustments be done
in small increments, at intervals about 30 seconds apart to allow for delayed
reaction of the alarm itself. The alarm low flow set point should now be set and the
red light activated.
7.
Readjust the enclosure airflow to its normal operating levels. The green light
should now be activated. Calibration is now complete.
Enclosure Operating In Flow Speed
Alarm Condition Set Point Speed
100 fpm
80 - 90 fpm
80 fpm
60 - 70 fpm
60 fpm
40 - 50 fpm
8.
Note: If the low airflow volume or sash opening cannot be adjusted, then a 1/4 to 1/3
of a turn counterclockwise can be adjusted to set the airflow alarm condition at 10-
25% below normal operating levels.
Guardian 500 Alarm Activation
The audio and visual alarm will activate approximately 10-30 seconds after an alarm condition is
detected. To temporarily mute the audible alarm, press and release the test/reset button.
NOTE:
After an alarm condition has been detected, the red light will stay on. The
audible alarm will remain muted until airflow returns to normal levels.
