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CPO-PC400-W/CPO-PC400-UW HVAC CONTROLLER
EN0B-0085 IE10 R0420
28
Connection to Modbus Modules
Fig. 19. Connection (L > 3 m) of RS485 interfaces 1, 2, or 3 (RS485 interface 1 shown) to a Modbus
NOTES:
—
N = max. 30 unit loads. Always power the CPO-PC400-W/CPO-PC400-UW and connected Modbus modules
with separate transformers. Termination resistors must be inserted directly into the terminals of the individual
Modbus modules.
—
Signal ground (signal reference) connection is recommended. For more information, see “General Information
on the RS485 Standard” section on page 7.
—
If the connected controllers do not have isolated RS485 interfaces and if they share a common ground between
the power supply and Earth ground, see the wiring diagram (Fig. 20) provided in Connection to Modbus devices
with non-isolated RS485 interfaces. This provides the best electrical noise rejection.
—
For communication cable lengths, transmission speeds, and termination, see “General Information on the
RS485 Standard” section on page 7.
Module #1
TX
5V
GND
Modbus
Isolaon
Barrier
RX
5V_ISO
GND_ISO
R
S
485+
R
S
485-
R
T
110VAC/230VAC
24VAC
Modbus
Module #N
F1
R
S
485+
R
S
485-
Common
L > 3m
R
T
Common
FG
N
D
24V0
24V~
CH1+
CH1-
GND1
R
S
485+
R
S
485-
CPO-PC400-W/CPO-PC400-UW