AERCO BMS 168 - Manual (Page 12)

WARNING!
Turn off AC input power to the BMS
to avoid electrical shock.
3.3 P
ULSE
W
IDTH
M
ODULATION
W
IRING
Pulse width modulation (PWM) wiring
connections are made between the BMS
JP2 terminal block and the Relay or I/O Box
terminals at each AERCO Boiler. Shielded
twisted-pair wire is recommended.
3.3.1 PWM Wiring At BMS
To wire boilers for pulse width modulation
(PWM), connect the boiler control wires in
ascending order according to the numbers
on the BMS (Figure 4). For example, the
control wiring for boiler 1 at the BMS would
be connected as follows:
• Positive control wire connects to JP 2,
terminal 1 (+).
• Negative control wire connects to JP 2,
terminal 2 (-).
• Shield wiring connects to the negative (-)
control wire at Section BLR 1, terminal 2.
The shield is not terminated at the boiler.
All shields must be terminated on the
BMS end. The wiring terminals labeled
SHIELD at terminal block JP3 of the
BMS are not internally connected to
ground and are only used as a place to
terminate the sensor shields. The pulse
width modulation shield can be
connected to any minus (-) terminal of
the PWM terminal strip (JP2).
3.3.2 PWM Wiring At The Boilers
The pulse-width modulation (PWM) control
wiring from the BMS to each boiler is
connected at each boiler’s relay box or
input/output (I/O) box, depending on the
type of control system used. Modular control
systems utilize a relay box as shown in
Figure 5 (KC1000) and Figure 7
(Benchmark). The newer C-More control
system utilizes an I/O box as shown in
Figure 6 and Figure 8.
Regardless of the type of control system
used, the PWM wiring is connected to the
BMS + and – terminals as shown in the
respective illustrations. It is imperative that
positive (+) and negative (-) polarity be
observed when making these connections.
All boilers follow the same control wiring
scheme.
When using pulse width modulation, the
BMS may be mounted up to 200 feet from
the boilers.
3.4 RS485 (M
ODBUS
) W
IRING
All Modbus Networks are implemented
using a “Master - Slave” technique. The
BMS can function as either a “Master”
controlling C-More Slaves or a “Slave”
controlled by a “Master” Energy
Management System (EMS) or Building
Automation System (BAS). Therefore, the
following paragraphs provide only an over-
view of the required wiring connections.
Detailed information and setup procedures
for RS485 Modbus networks are provided in
Modbus Communication Manual GF-114.
Refer to GF-114 prior to implementing any
RS485 networks using Modbus.
RS485 wiring connections are made using a
“Daisy-Chain” configuration. Shielded
twisted-pair wire from 18 to 24 AWG is
required for all RS485 wiring.
3.4.1 RS485 Wiring At BMS
RS485 wiring connections are made at the
BMS at connector JP11 which is labeled
RS485 TO BLRS. The location of this
RS485 connector is shown in Figure 9. In
addition, Figure 9 also shows the locations
of the external and internal RS232
connectors which are used to interface the
BMS to an EMS Master if required. The pin
assignments for the RS485 and RS232
connectors are shown in Figure 10.
3-2