AERCO BMK 1.5 LN July 2011 - Manual (Page 57)

CHAPTER 5: MODE OF OPERATION
PR2: 05/09/12 Page 57 of 152
Benchmark 1.5LN Low NOx Boiler
Operation and Maintenance Manual
OMM-0041_0D
GF-120
AERCO International, Inc. • 100 Oritani Dr. • Blauvelt, NY 10913 • Ph: 800-526-0288
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.
Direct Drive Startup 5.5.2
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)
NOTE
BMS Model 168 can utilize either pulse width modulation (PWM)
or RS485 Modbus signaling to the Boiler. BMS II Model 5R5-384
can utilize only RS485 signaling to the Boiler.
The BMS mode of operation is used in conjunction with an AERCO Boiler Management System.
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 programming, operation, and Header Sensor installation
details, see GF-108M (BMS Model 168) and GF-124 (BMS II Model 5R5-384), BMS Operations
Guides. 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:
MENU OPTION SETTING
Boiler Mode Direct Drive
Remote Signal BMS (PWM Input)
or
Network (RS485)
Refer to paragraph 3.3 for instructions on changing menu options.
BMS External Field Wiring 5.6.1
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
front of the boilers. Refer to the wiring diagram provided on the cover of the I/O Box.
Wiring connections for RS485 Modbus control are made between connector JP11 on the BMS