AERCO BMK 1.5 LN Dual Fuel Feb 2013 - Manual (Page 64)

CHAPTER 5: MODE OF OPERATION
Page 64 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
BMS External Field Wiring 5.6.1
Wiring connections for BMS control using PWM signaling are made between connector JP2
on the BMS panel (boilers 1 through 8), and the B.M.S. (PWM) IN terminals in the I/O Box
on the 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