Benchmark 2500 - 3000 Boilers
CHAPTER 5 – MODE OF OPERATION
OMM-0094_0E
AERCO International, Inc.
•
100 Oritani Dr.
•
Blauvelt, NY 10913
Page
67
of
204
GF-137
Ph.: 800-526-0288
03/20/2014
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 AERCO CONTROL SYSTEM (ACS)
NOTE
ACS is for installations with 9 or more boilers. It utilizes only RS-
485 signaling to the boiler. Installations with 1 to 8 boilers can use
BST (see Chapter 10).
The ACS mode of operation is used in conjunction with an AERCO Control System. The ACS
mode is used when it is desired to operate multiple units in the most efficient manner possible.
For this mode of operation, an ACS Header Sensor must be installed between 2 and 10 feet
downstream of the LAST boiler in the boiler plant's supply water header. The ACS can control
up to 40 boilers; Up to 32 via Modbus (RS-485) network communication. For ACS programming,
operation, and Header Sensor installation details, see ACS Operations Guide, GF-131. For
operation via an RS-485 Modbus network, refer to Modbus Communication Manual GF-114.
To enable the ACS Mode, the following menu settings must be made in the Configuration Menu:
Menu Option
Setting
Boiler Mode
Direct Drive
Remote Signal
Network (RS-485)
Refer to section 3.3 for instructions on changing menu options.
5.6.1 ACS External Field Wiring
Wiring connections for RS-485 Modbus control are made between the 485 A- and 485 B+
terminals on the ACS (boilers 9 through 40) and the RS-485 COMM terminals in the I/O Box on
the front of the boilers.