AERCO BMK 1.5 LN Dual Fuel Feb 2013 - Manual (Page 62)

CHAPTER 5: MODE OF OPERATION
Page 62 of 162 PR2: 05/09/12
Benchmark 1.5LN Dual-Fuel Low NOx Boiler
Operation and Maintenance Manual
OMM-0041_0C
GF-121
AERCO International, Inc. • 100 Oritani Dr. • Blauvelt, NY 10913 • Ph: 800-526-0288
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.
Remote Setpoint Startup 5.4.2
Since this mode of operation is factory preset and the setpoint is being externally controlled,
no startup instructions are necessary. In this mode, the REMOTE LED will light when the
external signal is present.
To operate the unit in the Manual mode, press the AUTO/MAN switch. The REMOTE LED
will go off and the MANUAL LED will light.
To change back to the Remote Setpoint mode, simply press the AUTO/MAN switch. The
REMOTE LED will again light and the MANUAL LED will go off.
5.5 DIRECT DRIVE MODES
The unit’s air/fuel valve position (% open) can be changed by a remote signal which is
typically sent from an Energy Management System (EMS) or from a Building Automation
System (BAS). The Direct Drive mode can be driven by a current or voltage signal within
the following ranges:
• 4-20 mA/1-5 VDC
• 0-20 mA/0-5 VDC
The factory default setting for the Direct Drive mode is 4-20 mA/1-5 VDC. With this setting,
a 4 to 20 mA signal, sent by an EMS or BAS is used to change the unit’s valve position
from 0% to 100%. A 4 mA/1V signal is equal to a 0% valve position, while a 20 mA /5V
signal is equal to a 100% valve position. When a 0-20 mA/0-5 VDC signal is used, zero is
equal to a 0% valve position.
In addition to the current and voltage signals described above, the Direct Drive mode can
also driven by a RS485 Modbus Network signal from an EMS or BAS.
When in a Direct Drive mode, the unit is a slave to the EMS or BAS and does not have a
role in temperature control. Direct Drive can be used to drive single, or multiple units.
NOTE
If a voltage, rather than current signal is used to
control the remote setpoint, a DIP switch adjustment
must be made on the CPU Board located in the
Control Box Assembly. Contact your local AERCO
representative for details.
To enable the Direct Drive Mode, the following menu setting must be made in the
Configuration Menu:
MENU
OPTION
SETTING
Boiler Mode Direct Drive
Remote
Signal
4-20mA/1-5V,
0-20mA/0-5V, or Network
Refer to paragraph 3.3 for instructions on changing menu options. If the Network setting is
selected for RS485 Modbus operation, a valid Comm Address must be entered in the Setup