Benchmark 1500 - 2000 Boilers
CHAPTER 5 – MODE OF OPERATION
Page 70 of 182 AERCO International, Inc. • 100 Oritani Dr. • Blauvelt, NY 10913 OMM-0097_0E
10/01/2015 Ph.: 800-526-0288 GF-142
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 9).
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
(0.61 and 3m) 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:
Table 5-4: ACS Mode Settings
Menu Option Setting
Boiler Mode Direct Drive
Remote Signal Network (RS485)
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.
Wire the units using shielded twisted pair wire between 18 and 22 AWG. Observe the proper
polarity for the ACS RS-485 COMM wiring connections. Shields should be terminated only at
the ACS and the boiler end must be left floating. Each unit’s wiring must conform to the above.
5.6.2 ACS Setup and Startup
This mode of operation is factory preset and the ACS controls the firing rate (air/fuel valve %
open position). There are no setup instructions for each individual unit.
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 ACS mode, simply press the AUTO/MAN switch. The REMOTE LED will
again light and the MANUAL LED will go off.
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