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CALIBRATING UNITS WITH LOW PRESSURE SENSORS
The Low Pressure alarm uses and absolute pressure sensor
and must be calibrated to the local altitude. To calibrate you
must; power up the unit. The green LED located in the center
of the camera bracket will turn on. After 30 seconds the LED
will begin to blink. At that time momentarily press the red
push button switch located next to the LED. LED will turn off
indicating unit is calibrated. Calibration is now complete. Unit
will store this base value and does not need to be recalibrated.
To recalibrate repeat the above procedure.
Alarm sensor contact is open when pressurized and closed
when the enclosure is no pressurized.
PRESSURIZING THE ENCLOSURE
Air is inserted in the enclosure through the Schreader valve
located on the top of the unit. A pressure release valve is
located under the housing cap located in this same
location. Air vents from the pressure release valve
between the housing top and the cap (Figure 4).
!
Before inserting air into the housing be sure the (2)
cap vents are free of obstructions such as ice or
debris (Figure 4).
Push button switch
Green LED
Figure 4
Vent holes
Schraeder valve
Pressurized housings provide maximum protection for CCTV
cameras and lenses. The charge of dry nitrogen inside the
housing eliminates the effects of moisture, dust, insects and
corrosive exhaust fumes. This allows a longer lifetime for your
surveillance equipment.
To pressurize the housing, you must have the following:
1. A tank of dry nitrogen
2. A regulator on the tank
3. A hose with air chuck to connect the regulator to the
housing’s intake valve
Dry Nitrogen
Nitrogen is a readily available. To obtain supplies, check your
local yellow pages for a medical or industrial gas provider. If
the tank is to be carried from location to location, a size of 40
cubic foot is recommended. This should be enough to refill
30 individual housings. Handle the tanks with care. Although
nitrogen is an inert gas, the tank is highly pressurized and if the
valve or regulator is damaged the tank could be dangerous.
Tanks of dry nitrogen can be kept for several years.
The Regulator
The tank will have a standard 580 fitting, but a regulator will be
required. A recommended regulator for the tank would be a
Harris #9296-15-580 or #425-15-580. For local distribution you
can contact Harris at 800-241-0804.
The Hose
The purge valve, called a “Schraeder” or “dill” valve, is similar
to the air intake valve on car or bicycle tires. To connect the
regulator to the purge valve on the housing, you’ll need a hose
with a ¼” barb on one end and an air chuck on the other. The
barb connects to the regualtor, the air chuck to the Schraeder
valve. These hoses can be obtained at local auto parts stores.
Pressurizing and Purging the Housing
(
to remove moisture
)
Set the gauge on the regulator to between 10 and 20 psi.
Place the air chuck on the Schraeder valve, just as you would
on a tire, and press down to begin filling. Continue until you
hear air venting from the pressure relief valve (located under
plastic cover–see Figure 3 on previous page). Drain all air in
housing and refill housing . Repeat an additional 2 times. After
refilling for the third time, check pressure in housing. It should
read between 5 to 7 psi.
