Specifications

MODBUS COMMUNICATION MANUAL
4-11
4.4 MODBUS NETWORK WIRING DIAGRAMS
Sample Modbus Network wiring diagrams for the basic circuit configurations are provided in
paragraphs 4.4.1 through 4.4.3. It should be noted that these diagrams are only intended as a
guide and do not include all possible scenarios. If a third-party EMS is being utilized, refer to
the manufacturer’s manual prior to attempting any network wiring connections.
CAUTION
It is imperative that polarity be maintained between all Modbus Network
connections. The Network will not operate if the proper polarity is not maintained.
Also, twisted-pair wiring shield should only be terminated at the controlling
Master Controller for the Modbus Network. Shields must not be le
4.4.1 Wiring Diagrams for Master EMS Controlling BMS Slave With Legacy (PWM)
Boilers
Figure 4-9 provides a sample wiring diagram for a BMS Unit being controlled by an EMS Master
equipped with a RS485 port.
4.4.2 Wiring Diagram for Master BMS Controlling Networked C-More Slaves
Wiring connections for the “Network” Boilers are made at the BMS RS485 port as shown in
Figure 4-10. In addition, up to 8 “Legacy” Boilers can be wired to the PWM J2P terminal strip to
allow control of up to 40 Boilers by one BMS. The BMS PWM terminal connections can also be
used to connect AERCO Boilers which utilize older types of control systems, such as Modular
Control Boxes, or C-More Controllers equipped with software version 1.61 or lower. Refer to
BMS Manual GF-108 for additional setup details for the PWM “Legacy” Boilers.
4.4.3 Wiring Diagram For EMS Master Controlling C-More Controller Slaves
Figure 4-11 provides a sample wiring diagram for an EMS equipped with a RS485 port. If the
EMS contains a 4-wire RS485 port, refer to Figure 4-9, Detail “A” for additional wiring details.