06/05/13
AERCO International, Inc.
•
100 Oritani Dr.
•
Blauvelt, NY 10913
•
Ph: 800-526- 0288
Page
67
of
112
GF-115-C
Modulex E8 Controller and BCM
Operations and Maintenance Manual
OMM-0084_0D
In the event that the external control signal from the Master BMS II or ACS, EMS, or BAS is lost,
the BCM will assume control of the Modulex Boilers, if enabled. When this occurs, the BCM will
maintain the boiler at a constant setpoint based on the resistor installed between terminals 6
and 7 of connector Y2 (see
Figure 7-5
). In addition, the BCM Fault Relay will be activated and
the red Fault LED (DL2) will light.
7.4.2 Physical Modbus RS485 Wiring
Modbus RS485 devices should be wired in a “Daisy-Chain” configuration similar to the example
shown
Figure 7-6
. DO NOT wire the units in a “Star” configuration where all devices are
connected to a central point (node).
Figure 7-6. Typical Daisy-Chain Modbus/RS485 Network
The physical wiring connections for a Modbus Network should be made using shielded twisted-
pair wire, from 18 to 24 AWG. Examples of suitable wire are: Belden # 9841, #8761, #3105A, or
equivalent.
Modbus wiring connections are made at terminals 1 and 2 of BCM connector Y2 as shown in
Figure 7-7
.
Y2
Y3
Y4
Y1
SW1
A1
I
0
MODBUS B
(+)
BCM FRONT VIEW
7 6 5 4 3 2 1
Y2
MODBUS A
(-)
Figure 7-7: BCM Modbus (RS485) Connections
MASTER
SLAVE
#1
SLAVE
#2
SLAVE
#3
SLAVE
#4
SLAVE
#5
