Instruction manual

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CALIBRATING UNITS WITH LOW PRESSURE SENSORS
(Not supplied on 12Vdc units)
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 rell 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 tting, 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 regulator, 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 lling. 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 rell housing . Repeat an additional 2 times. After relling for the
third time, check pressure in housing. It should read between 5 to 7 psi.