Det-Tronics R7495D UV/IR Flame Detection System - Manual (Page 12)

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 cabinet.
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
used, the seal must be located between the swivel and
the detector. When an explosion-proof installation is
required, an additional seal must also be installed at
any point where the conduit enters a non-hazardous
area. When pouring a seal, the use of a fiberdam is
required to assure proper formation of the seal. The
seals should never be poured in temperatures that are
below freezing, since the water in the sealing com-
pound will freeze and the compound will not dry proper-
ly. Contamination problems can then result when tem-
peratures rise above the freezing point and the com-
pound thaws. The shielding of the cable should be
stripped back to permit the seal to form around the indi-
vidual leads, rather than around the outside of the
shield. This will prevent any siphoning action that might
occur through the inside of the shield. The electrical
continuity of the shield must be maintained through the
seal by means of the shield drain wire.
Moisture in the air can be trapped within sections of
conduit and can condense and accumulate at the base
of vertical conduit runs. To eliminate this condition,
explosion-proof drains and breathers should be
installed to automatically bleed off accumulated water.
It is recommended that the detector be oriented with the
conduit opening at the bottom or at either side of the
device. This will reduce the possibility of moisture
entering the junction box through the conduit entry and
also ensure that the oi test lamps are not in a position
that would make the detector overly susceptible to oi
faults. Whenever possible, slope the conduit run down-
ward from the detector. Do not use conduit runs that
enter the device from the top. See Figure 10 for identifi-
cation of the detector parts of interest when mounting,
and Figure 11 for an example of vertical detector mount-
ing.
DETECTOR MOUNTING AND WIRING PROCEDURE
The following procedure should be used for mounting
and wiring the C7052J.
1. Detectors should be located in positions best suited
for covering the area to be protected. Whenever
practical, they should be placed where they will be
easily accessible for cleaning and other periodic
servicing. Particular attention should also be paid
to potential false alarm sources within the cone of
vision of the detector, such as distant arc welding,
rotating fan blades, surface vibration of an IR
source, and movement of people or machines
between the detector and an IR source, all of which
could allow a flickering IR signal to reach the detec-
tor. Rain or ice can absorb radiation, which can
reduce the capability of the detector. For outdoor
applications, aim the detector downward to mini-
mize the buildup of water or ice on the detector
viewing windows and to prevent the cone of vision
from scanning the horizon. This minimizes
response to distant radiation sources outside the
protected area. See Figure 11 for an example of
vertical detector mounting.
NOTE
The wiring procedures in this manual are intended
to ensure proper functioning of the device under
normal conditions. However, because of the many
variations in wiring codes and regulations, total
compliance to these ordinances cannot be guaran-
teed. Be certain that all wiring complies with appli-
cable regulations that relate to the installation of
electrical equipment in a hazardous area. If in
doubt, consult a qualified electrician before wiring
the system.
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