AERCO Modulex E8 Controls Guide - Manual (Page 69)

PR1: 11/30/12 Page 69 of 112
GF-115-C Modulex E8 Controller and BCM
Operations and Maintenance Manual
OMM-0084_0D
AERCO International, Inc. • 100 Oritani Dr. • Blauvelt, NY 10913 • Ph: 800-526- 0288
7.5.2 BCM Controller Terminating Resistor and Bias
BCMs can function only as Slave devices on a Modbus Network. Since the Slaves are
connected in a “Daisy-Chain” configuration, the terminating resistor must be enabled only in the
last BCM Controller in the chain. Enabling the terminating resistor is accomplished by
positioning jumper JP1 as shown in Figure 7-9 only on the BCM Board contained in the last
BCM Controller.
As mentioned in
paragraph 7.5.1, when the controlling Master is an EMS or BAS, pull-down
bias may be implemented by connecting a 1K ohm resistor as shown in Figure 7-9. DO NOT
install this bias resistor if the controlling Master is an AERCO BMS II or ACS. Bias will be
provided by the BMS II/ACS DIP switches. The last unit in the chain must be energized (even if
disabled) to enable bias.
Y2 Y3 Y4
Y1
SW1 A1
I
0
BCM FRONT VIEW
7 6 5 4 3 2 1
Y2 JP2 JP1
T C
V
JUMPER
SHOWN IN
“TERMINATED”
POSITION
1K OHMS
PULL-DOWN
BIAS
RESISTOR
DO NOT
INSTALL BIAS
RESISTOR
WHEN BMS II
IS “MASTER”
Figure 7-9: BCM Loop Termination and Bias