AERCO Modbus Communications Manual - Manual (Page 61)

Chapter 4
MODBUS
Communication GF-114
Hardware Setup & Installation USER MANUAL OMM-0035_0C
05/18/12 AERCO International, Inc. • 100 Oritani Dr. • Blauvelt, NY 10913 • Ph: 800-526-0288 Page 61 of 200
DB9 (FEMALE)
PIN 5
GND
PIN 3
TxD
PIN 2
RxD
5 1
9 6
RXD TXD GND
RS232
JP
12
+(B) -(A) SHLD
RS485
TO BLRS
JP
11
NOT
USED
EXTERNAL RS232 PORT
INTERNAL RS485 & RS232 PORTS
RS485 PORT RS232 PORT
Figure 4-4: BMS RS232 & RS485 Connectors
4.2.2 BMS II/ACS Slave To EMS Master Wiring Connections
Wiring connections between an EMS Master and an AERCO BMS II/ACS Slave are made at the
internal RS232 port terminals behind the wiring compartment cover of the BMS II/ACS. These
connections are shown in Figure 4-5. These terminals are labeled RXD, TXD and 232 ISO GND.
In addition, Figure 4-5 shows the internal RS485 terminals used to interface the boilers to the
Modbus Network.
If the EMS Master being used contains only an RS485 port (2-wire or 4-wire), an RS485-to-
RS232 Converter is required. A BMS II/ACS option is available with a built-in RS485-to-RS232
Converter to simplify connection between the EMS and BMS II/ACS. A separate external
converter can also be used if desired.
Simplified block diagrams showing the internal and external connection options between the
BMS II/ACS and EMS are shown in Figure 4-6.