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Benchmark 2.0LN Dual-Fuel Low NOx Boiler
CHAPTER 5: MODE OF OPERATION
5.5.1
Direct Drive Field Wiring
The only wiring connections necessary for Direct Drive mode are connection of the remote
signal leads from the source to the unit's I/O Box. For either a 4-20mA/0-5V or a 0-20mA/0-5V
setting, the connections are made at the ANALOG IN terminals in the I/O Box. For a Network
setting, the connections are made at the RS-485 COMM terminals in the I/O Box. The signal
must be floating, (ungrounded) at the I/O Box and the wire used must be a two wire shielded
pair from 18 to 22 AWG. Polarity must be observed. The source end of the shield must be
connected at the source. When driving multiple units, each unit's wiring must conform to the
above.
5.5.2
Direct Drive Startup
Since this mode of operation is factory preset and the valve position is being externally
controlled, no startup instructions are necessary. In this mode, the REMOTE LED will light when
the signal is present.
To operate the unit in manual mode, press the AUTO/MAN switch. The REMOTE LED will go
off and the MANUAL LED will light.
To change back to the Direct Drive mode, simply press the AUTO/MAN switch. The REMOTE
LED will again light and the MANUAL LED will go off.
5.6 BOILER MANAGEMENT SYSTEM (BMS)
BMS Model 168 can utilize either pulse width modulation (PWM) or
RS485 Modbus signaling to the Boiler. The BMS II and the ACS
(AERCO Control System) can utilize only RS485 signaling to the Boiler.
The BMS mode of operation is used in conjunction with an AERCO Boiler Management System
(BMS or BMS II) and the AERCO Control System (ACS). The BMS mode is used when it is
desired to operate multiple units in the most efficient manner possible. For this mode of
operation, a BMS Header Sensor must be installed between 2 and 10 feet downstream of the
LAST boiler in the boiler plant's supply water header. The BMS can control up to 40 boilers; 8
via pulse width modulation (PWM) and up to 32 via Modbus (RS485) network communication.
For BMS/BMS II/ACS programming, operation, and Header Sensor installation details, see GF-
108M (BMS Model 168), GF-124 (BMS II Model 5R5-384), and GF-131 (ACS) Operations
Manuals. For operation via an RS485 Modbus network, refer to Modbus Communication
Manual, GF-114.
To enable the BMS Mode, the following menu settings must be made in the Configuration
Menu:
Refer to paragraph 3.3 for instructions on changing menu options.
5.6.1
BMS External Field Wiring
Wiring connections for BMS control using PWM signaling are made between connector JP2 on
the BMS panel (boilers 1 through 8), and the B.M.S. (PWM) IN terminals in the I/O Box on the
AERCO International, Inc. • 100 Oritani Dr. • Blauvelt, NY 10913 • Ph: 800-526-0288
Page 60 of 158
Operation and Maintenance Manual
NOTE
MENU OPTION
Boiler Mode
Direct Drive
Remote Signal
BMS (PWM Input)
or
Network (RS485)
SETTING
GF-127
OMM-0052_0E
PR2: 04/22/13
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