CHAPTER 5: MODE OF OPERATION
PR2: 04/22/13 Page
61
of
158
Benchmark 2.0LN Dual-Fuel Low NOx Boiler
Operation and Maintenance Manual
OMM-0052_0E
GF-127
AERCO International, Inc.
•
100 Oritani Dr.
•
Blauvelt, NY 10913
•
Ph: 800-526-0288
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
(boilers 9 through 40) or JP6 on BMS II/ACS (boilers 1-32) and the RS485 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 B.M.S. (PWM) IN and/or RS485 COMM wiring connections. Shields should be
terminated only at the BMS/BMS II/ACS and the boiler end must be left floating. Each unit’s
wiring must conform to the above.
BMS Setup and Startup
5.6.2
This mode of operation is factory preset and the AERCO BMS/BMS II/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 BMS 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 the BMS and ACS can be utilized for the Combination Mode, but
not the BMS II.
A Combination Control System (CCS) is one that uses multiple boilers to cover both space-
heating and domestic hot water needs. An AERCO Boiler Management System (BMS) Model
168 and a Combination Control Panel (CCP) or an ACS and an ACS Relay Panel (optional,
depending on applications) 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 the
domestic hot water are capable of switching between constant setpoint and BMS modes of
operation. 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.
When the space-heating load is such that all the space-heating boilers are at the 100% valve
position, the BMS/ACS will then operate the domestic boilers to become space-heating boilers,
provided the domestic hot water load is satisfied. If the domestic hot water load is not satisfied,
the combo boiler(s) remain on the domestic hot water load. If the combo boilers switch over to
space heating, but there is a call for domestic hot water, the combo units will resume heating
water for domestic needs.
When the combo units are satisfying the domestic load they are in constant setpoint mode of
operation. When the combo units switch over to space heating, their mode of operation changes
to the BMS mode. For more information concerning the operation of the Combination Control
Panel see the AERCO CCP-1 literature (BMS 168 applications) and TAG-0050 (ACS).
Combination Control System Field Wiring
5.7.1
Wiring for this system is between the BMS Model 168 panel, the CCP and the B.M.S. (PWM) IN
terminals in the I/O Box. For ACS applications, the wiring is between the ACS panel, the ACS
