Det-Tronics C7050 A, C, G, P UV Flame Detector - Manual (Page 12)

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 be trapped within sections of con-
duit, therefore the use of conduit seals is required to pre-
vent damage to electrical connections caused by con-
densation 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 detector as possible. In no
case should this seal be located more than 18 inches
(46 cm) from the detector. If a conduit swivel is used, a
seal
must be located between the detector and the
swivel. When local codes require an explosion-proof
installation, an additional seal is also required 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 compound will freeze and
the compound will not dry properly. Contamination prob-
lems can then result when temperatures rise above the
freezing point and the compound thaws. The shielding
of the cable should be stripped back to permit the seal
to form around the individual leads, rather than around
the outside of the shield. This will prevent any siphoning
action that might occur through the inside of the shield.
It is recommended that conduit breathers also be used.
In some applications, alternate changes in temperature
and barometric pressure can cause “breathing,” which
allows the entry and circulation of moist air throughout the
detector and connected conduit. Joints in the conduit
system and its components are seldom tight enough the
prevent this “breathing.” Moisture in the air can con-
dense at the base of vertical conduit runs and equipment
enclosures, and can build up over a period of time. This
can be detrimental to electronic devices. To eliminate this
condition, explosion-proof drains and breathers should
be installed to automatically bleed off accumulated water.
Cable made specifically for harsh, salt-water environ-
ments must be used in areas where high humidity or salt
water is a problem. In all cases, typical cable insulation
resistance should measure 100 megohms or more, using
a high voltage insulation tester (megohmmeter). If cable
resistance drops below 10 megohms, it should be
replaced immediately to avoid shorting.
IMPORTANT
Disconnect the detectors and controller before
applying a megohmmeter to the cable.
When using steel wire armored or mineral-insulated cop-
per-sheathed cables, select an approved gland with a
watertight compression stage and an overall gland
shroud for outdoor applications. A sealing washer must
be fitted between the gland and the conduit entry to
ensure IP66 rating.
NOTE
The wiring procedures in this manual are intended to
ensure proper functioning of the device under nor-
mal conditions. However, because of the many vari-
ations in wiring codes and regulations, total compli-
ance to these ordinances cannot be guaranteed. Be
certain that all wiring complies with applicable regu-
lations that relate to the installation of electrical
equipment in a hazardous area. If in doubt, consult
a qualified official before wiring the system.
DETECTOR POSITIONING AND DENSITY
The detector has a nominal 90° cone of vision. What this
means in practical terms can be understood by reference
to a typical installation. Consider an application such as
a loading rack with a ceiling height of 25 feet (7.5 meters),
and assume it is desired to have complete detector cov-
erage at floor level. If a detector is mounted 2 feet (0.6
meter) from the ceiling and pointed straight down, the dis-
tance from the detector to the designated level would be
23 feet (7 meters). Because of its 90° cone of vision, the
detector would cover a circular area with a diameter of 46
feet (14 meters) at the designated level. A simple layout
of the area to be covered will easily reveal the number of
detectors required to completely supervise the designat-
ed area. In general, detectors should be placed as close
as practical to the probable hazard.
NOTE
Do not mount UV detectors close to the ceiling in
enclosed areas if dense smoke can be expected to
accumulate at the onset of a fire. Mounting the
detector on side walls a few feet (or about 1 meter)
down from the ceiling will normally allow time for
the detectors to respond before they are affected
by smoke rising to the ceiling. It is also advisable
to shorten any time delay settings for applications
where smoke may accumulate during a fire. If
dense smoke can be expected to accumulate prior
to the presence of flame (as in an electrical fire), do
not use UV detectors alone.
MOUNTING THE DETECTOR
The following procedure should be used for mounting
and wiring the detectors.
1. Detectors should be located for the best unobstruct-
ed view of the area to be protected. Detectors must
be accessible for cleaning the viewing window and
reflector rings. Care must be taken so that dirt or
other foreign material will not accumulate and
obscure the detector viewing window. For outdoor
applications, the detectors should be pointed down-
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