Det-Tronics C7052J UV/IR Flame Detector used with R7494, R7495 Controller - Manual (Page 9)

The C7052J uses a single frequency IR sensing device
with detection limited to the hot CO2 emission peak,
therefore, it cannot be used to detect fires that do not
contain carbon, such as hydrogen, sulfur, burning met-
als, or other non-hydrocarbons without thorough testing.
INSTALLATION
Detector Positioning
When determining the proper number and positioning of
detectors needed for adequately protecting any given
installation, it is essential to consider the cone of vision
of the detector. The C7052J Detector has a nominal 80
degree cone of vision with the highest sensitivity along
its central axis. Refer to Figure 4. Careful observation
of this graph reveals that at 50 percent of the maximum
detection distance, the cone of vision is still 80 degrees.
As the detection distance increases beyond 50 percent,
the cone of vision gradually decreases. For example,
the C7052J will detect a 1 foot by 1 foot gasoline fire at
50 feet. Therefore, we can assume that at 25 feet (50%
maximum distance) the cone of vision will be 80
degrees. If the fire increases in size, both the maximum
detection distance and the cone of vision at longer dis-
tances will be increased.
It is also important to note that as the distance increases
between the detector and the fire source, the time need-
ed for the detector to respond to a fire of a given size
also increases (fastest response requires maximum fire
signal). The intensity of the radiation reaching the
detector decreases with distance. For fastest response
time, locate the detector as close as possible to the
anticipated fire source.
The following recommendations should be observed in
designing or installing any fire detection system:
— Use enough detectors to adequately cover the pro-
tected area with overlapping cones of vision.
— For fastest response time, position the detectors as
close as possible to the anticipated fire source.
— Aim the detector as directly as possible at the antic-
ipated fire source.
— If possible, conduct actual flame tests to verify cor-
rect detector positioning and proper system opera-
tion.
Whenever possible, the detector should be positioned
in a manner that will minimize the buildup of contami-
nants on the viewing window and
oi ring. Substances
such as snow, ice, dirt, oil, paint overspray, and numer-
ous other commonly encountered materials are capable
of attenuating UV or IR radiation and adversely affecting
detector response.
For outdoor applications, the detector should be aimed
downward to minimize the buildup of water or ice on
the detector viewing window and to prevent it from
scanning the horizon. This minimizes the response to
distant radiation sources outside the protected area.
The detector should not be placed where smoke can
obscure its view of the hazardous area. For indoor
applications, if dense smoke is expected to accumulate
at the onset of a fire, mounting the detector on a side
wall a few feet (1 meter) down from the ceiling will nor-
mally allow enough time for the unit to respond before it
is affected by rising smoke. The detector should be
located where it can be easily accessed for periodic
maintenance, testing and cleaning.
Wiring Requirements
The system should be wired using four conductor
shielded cable, at least 18 gauge (1.024 mm diameter).
The length of cable should be considered when wiring
the system to ensure that a minimum input voltage of 18
vdc is present at the detector. The cable length should
not exceed 2000 feet. In applications where the wiring
cable is installed in conduit, the conduit should not be
used for wiring to other electrical equipment. Foil type
shielded cable is recommended to protect from electro-
magnetic and radio frequency interference. When
using cables with shields, the shield should be insulated
at the detector and grounded only at the control cabi-
net.
NOTE
It is important to use cable that is suitable for the
installation environment. In applications involving
high humidity or salt water, use a cable that is
made specifically for harsh, salt water environ-
ments. In all cases, typical cable insulation resis-
tance should be at least 100 megohms. If the
resistance drops below 10 megohms, the cable
could be deteriorating and should be replaced to
avoid shorting. When testing the insulation resis-
tance, disconnect the leads from the detector/con-
troller before connecting the megohmmeter (insula-
tion tester) to the cable.
Since moisture can be detrimental to electronic devices,
it is important that moisture not be allowed to come in
contact with the electrical connections of the system.
Moisture in the air can become trapped within sections
of conduit, therefore the use of conduit seals is required
to prevent damage to electrical connections caused by
condensation within the conduit. These seals must be
water-tight and explosion-proof and are to be installed
even if they are not required by local wiring codes. A
seal must be located as close to the C7052J as possi-
ble. In no case should this seal be located more than
18 inches (46 cm) from the unit. If a conduit swivel is
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