AERCO BMK 1000 - Manual (Page 74)

Benchmark 750/1000 Boiler Installation, Operation & Maintenance Manual
CHAPTER 5 – MODE OF OPERATION
Page 74 of 192 AERCO International, Inc. • 100 Oritani Dr. • Blauvelt, NY 10913 OMM-0082_0J
05/21/2014
Ph.: 800-526-0288
GF-130
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 (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.
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 ACS mode, simply press the AUTO/MAN switch. The REMOTE LED will
again light and the MANUAL LED will go off.
5.7 COMBINATION CONTROL SYSTEM (CCS)
NOTE
Only ACS can be utilized for the Combination Control System.
A Combination Control System (CCS) is one that uses multiple boilers to cover both space-
heating and domestic hot water needs. An AERCO Control System (ACS) and An optional ACS
Relay Box are necessary to configure this system. Typically, an adequate number of boilers are
installed to cover the space-heating load on the design day, however one or more units are
used for the domestic hot water load.
The theory behind this type of system is that the maximum space-heating load and the
maximum domestic hot water load do not occur simultaneously. Therefore, boilers used for
domestic hot water are capable of switching between constant setpoint and ACS control.
For a typical CCS, an adequate number of boilers are installed to cover the space-heating load
on the design-day. However, one or more units are used for the domestic hot water load as well.
These boilers are the combination units and are referred to as the combo boilers. The combo
boilers heat water to a constant setpoint temperature. That water is then circulated through a
heat exchanger in a domestic hot water storage tank.