Honeywell ComfortPoint Open CPO-PC400-W Manual page 22

CPO-PC400-W/CPO-PC400-UW HVAC CONTROLLER
Connection to BACnet MSTP Buses with Isolated Transceivers
R
T
5V_ISO
GND_ISO
Isola on
Barrier
5V
RX TX
GND
CPO-PC400-W/CPO-PC400-UW
Fig. 13. Connection (L > 3 m) of RS485 interfaces 1, 2, or 3 (RS485 interface 1 shown) to a BACnet Bus
NOTES:
— Always power the CPO-PC400-W/CPO-PC400-UW with a transformer separate to the connected BACnet MSTP
modules.
— N = max. 30 modules.
— Signal ground (signal reference) connection is recommended if not all devices are electrically isolated. 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 diagrams (Fig. 14) provided in Recommended connection for
BACnet MSTP Buses 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. For fusing, see "Fusing" section on page 11.
— Termination resistors must be inserted directly into the terminals of the individual BACnet MSTP modules. In
the above figure, the CPO-PC400-W/CPO-PC400-UW is shown operating as the Master BACnet controller;
EN0B-0085 IE10 R0420
110VAC/230VAC
24VAC
F1
22
L > 3m
CP-VAV/SPC #1 CP-VAV/SPC #N
R
T