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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 64. Nodes are any device connected to the loop and
include controllers but do not include the EOL terminators.
To install more than 64 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.
An optional signal is the alarm relay output available on the NO (NORMALLY OPEN), NC (NORMALLY
CLOSED ) and R.COM (RELAY COMMON) terminals. The R.COM terminal is not connected to the power
supply COM terminal, the relay output is completely isolated. The relay contacts may be connected to a
controller Digital Input (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
particulate matter sensor relay and a large fan for example. See Figure 9.
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
Figure 9
EOL
EOL
EOL
OFF
ON
Digital Input
Digital Input
Digital Input
NO
R. COM
NC
Controller
IN-GE-PMRMCXXX-05
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