Installation Instructions

Table Of Contents

CPO-PC400-W/CPO-PC400-UW HVAC CONTROLLER

EN0B-0085 IE10 R0420 22

Connection to BACnet MSTP Buses with Isolated Transceivers

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;

GND

CP-VAV/SPC #1

Isolaon

Barrier

5V_ISO

GND_ISO

RS485+

RS485-

110VAC/230VAC

24VAC

CP-VAV/SPC #N

RS485+

RS485-

FGND

L > 3m

RS485+

RS485-

FGND

CH1+

CH1-

GND1

24V~

24V0

FGND

CPO-PC400-W/CPO-PC400-UW