Det-Tronics 505 Combustible Gas Detector Transmitter with Combustible Gas Sensor CGS - Manual (Page 10)

7 95-8472 3.1
Conduit Seals, Drains, and Breathers
The Model 505 Transmitter is designed and approved for
use in hazardous areas where explosion-proof equipment
certification is required. When installing the Model 505
in such areas, explosion-proof conduit seals should
be installed within 18 inches (46 cm) of the transmitter
housing. Conduit seals prevent the passage of vapors
or flames through the conduit. Seals are recommended
even if they are not required by local wiring codes.
Conduit systems are never completely air-tight. As a
result, significant amounts of condensation can form
within the conduit system. Therefore, it is important to
take proper precautions during installation to ensure that
moisture will not cause damage to the transmitter or other
components of the system.
Conduit raceways should be inclined so that water will flow
to low points for drainage and will not collect on conduit
seals or inside enclosures. If this is not possible, install
conduit drains above the seals to prevent the collection
of water, or install a drain loop below the detector with a
conduit drain at the lowest point of the loop.
Conduit drains should be installed at water collection
points to automatically drain accumulated moisture.
Conduit breathers should be installed at upper locations
to provide ventilation and allow water vapor to escape.
At least one breather should be used with each drain.
When using steel wire armored or mineral-insulated
copper-sheathed cable, 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/cable entry
to ensure IP66 rating.
MODEL 505 WIRING
Wire the Model 505 as shown in Figure 6.
SENSOR SEPARATION
For maximum EMI/RFI protection, it is preferable to
mount the sensor directly to the Model 505 junction
box. However, in many cases it is desirable to locate
the sensor in a remote location where early gas detection
is most probable, and install the transmitter in an easy-
access location. In this case, a Sensor Termination Box
(available from Detector Electronics) should be used to
install the sensor separately from the transmitter. See
Figure 7.
A continuous, three conductor cable with an overall foil
shield must be used with the sensor separation kit. The
cable shield drain wire should be cut back and insulated
within the sensor junction box and connected to earth
ground at the transmitter junction box. Failure to use a
shielded cable or properly ground the shield is likely to
result in nuisance alarms caused by EMI/RFI problems.
The maximum separation distance between the sensor
and transmitter is limited by the electrical resistance of
the connecting wiring, which is a function of the gauge
of the wire being used. Table 1 gives the recommended
and absolute maximum sensor separation distances. If
the distance is less than the recommended maximum,
no adjustment to sensor voltage is required, although
measurement of the sensor voltage is recommended to
verify proper sensitivity. If the distance is greater than
the recommended maximum, refer to the “Sensor Voltage
Adjustment” section.
Sensor separation installations with the Model 505 require
a special terminal plug for connecting the sensor wiring
to the transmitter. This connector (P/N 102883-001) is
included with the Sensor Termination Box, and is also
available separately for existing installations.
NOTES:
1. DO NOT APPLY POWER TO THE TRANSMITTER WITH THE JUNCTION BOX COVER
REMOVED UNLESS THE AREA HAS BEEN DE-CLASSIFIED.
2. POSITION THE TRANSMITTER WITH THE SENSOR POINTING DOWN.
3. THE TRANSMITTER JUNCTION BOX SHOULD BE ELECTRICALLY CONNECTED TO
EARTH GROUND.
4. ATTACH THE SENSOR TO THE JUNCTION BOX TIGHTLY ENOUGH TO ENSURE AN
EXPLOSION-PROOF INSTALLATION, HOWEVER, DO NOT OVERTIGHTEN. LUBRICATE
THE THREADS WITH THE CORRECT LUBRICANT TO EASE INSTALLATION AND
FUTURE REPLACEMENT. SILICONE BASED LUBRICANTS MUST NEVER BE USED.
5. CABLE SHIELDS SHOULD BE CONNECTED TO EARTH GROUND AT ONE END ONLY.
6. SHIELDS SHOULD BE STRIPPED BACK FROM CONDUCTORS ONLY WITHIN THE
JUNCTION BOX ENCLOSURE.
–
SIG
RED
SENSOR
WHT BLK
+
CONTROLLER
4 TO 20 MA
24 VDC
–
–
+
+
C1938
Figure 6—Model 505 Transmitter Wiring Without Sensor Separation