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If the device includes the optional network connection, use
twisted shielded pair to connect to the terminals marked
A-, B+ and SHLD (SHIELD). The positive wire connects to B+,
the negative to A- and the cable shield must be connected
to the SHLD terminal on each device. The shield wire should
be connected to earth ground at one end of the network
only. See Figure 7. If the device is installed at either end of
an RS-485 network, an end-of-line (EOL) termination resistor
(121 ohms) should be installed in parallel with the A- and B+
terminals. This device includes a network termination resistor
and jumper that can be used to connect the EOL resistor on
the PCB. Simply move the jumper to the EOL position and
no external resistor is required. See Figure 8.
A network segment is a single shielded wire loop run between
several devices (nodes) in a daisy chain configuration. The
total segment length should be less than 1220 meters
(4000 feet) and the maximum number of nodes on one
segment length is 128. Nodes are any device connected
to the loop and include controllers but do not include
the EOL terminators. To install more than 128 devices, or
to increase network length, repeaters will be required for
proper communication. The maximum daisy chain length
(segment) depends on transmission speed (baud rate),
wire size and number of nodes. If communication is slow or
unreliable, it may be necessary to wire two daisy chains to
the controller with a repeater for each segment.
The toxic gas sensor may have one or two optional relays
installed. The relays are Form C type with both a normally
open (NO) and a normally closed (NC) contact. The relay
contacts may be connected to controller Digital Inputs (DI) for status monitoring or used to directly control
an alarm or ventilation fan. Do not exceed the device contact ratings. In some cases, a separate control
relay may be used between the sensor relay and a large fan for example.
Figure 10
NC1
COM1
NO1
Digital
Input
Figure 7
Set EOL Jumper
Building Controller
Device 01
Device 02
Device 03
Connect Shield One End Only
PWR
COM
PWR
COM
PWR
COM
SHLD
B+
A-
SHLD
B+
A-
SHLD
B+
A-
BACnet® Master
24 Vac / dc
Common
Shield
B+
A-
Building Controller
Device 01
Device 02
Device 03
Connect Shield One End Only
PWR
COM
PWR
COM
PWR
COM
SHLD
B+
A-
SHLD
B+
A-
SHLD
B+
A-
BACnet® Master
24 Vac / dc
Common
Shield
B+
A-
External 24 Vdc Power
Supply or 24 Vac
Transformer
Figure 8
EOL
EOL
EOL
OFF
ON
Figure 9
Main Unit
Remote NO
2
Remote NO
2
Wiring
RP
RC
SCLP
SCLM
SDAP
SDAM
12V
COM
CLP
CLM
DAP
DAM
IN-GE-GDTXXX-06
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