Honeywell ComfortPoint Open CPO-PC400-W Manual page 28

CPO-PC400-W/CPO-PC400-UW HVAC CONTROLLER
Connection to Modbus Modules
R
T
GND_ISO 5V_ISO
Isola on
Barrier
5V
TX
GND RX
CPO-PC400-W/CPO-PC400-UW
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.
EN0B-0085 IE10 R0420
110VAC/230VAC
24VAC
F1
28
L > 3m
Modbus
Module #1
Modbus
Module #N
R
T