Aerco Benchmark 3.0LN Series, Installation, Operation & Maintenance Instructions Manual

Page: 46 / 127

MODE OF OPERATION
5-4
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 BOILER MANAGEMENT SYSTEM
(BMS)
NOTE
BMS Model 168 can utilize either pulse
width modulation (PW M) or RS485
Modbus signaling to the Boiler. BMS II
Model 5R5-384 can utilize only RS485
signaling to the Boiler.
The BMS mode of operation is used in
conjunction with an AERCO Boiler Management
System. The BMS mode is used when it is
desired to operate multiple units in the most
efficient manner possible. For this mode of
operation, a BMS Header Sensor must be
installed between 2 and 10 feet downstream of
the LAST boiler in the boiler plant's supply water
header. The BMS can control up to 40 boilers; 8
via pulse width modulation (PW M) and up to 32
via Modbus (RS485) network communication.
For BMS programming, operation, and Header
Sensor installation details, see GF-108M (BMS
Model 168) and GF-124 (BMS II Model 5R5-
384), BMS Operations Guides. For operation via
an RS485 Modbus network, refer to Modbus
Communication Manual GF-114.
To enable the BMS Mode, the following menu
settings must be made in the Configuration
Menu:
MENU OPTION SETTING
Boiler Mode Direct Drive
Remote Signal BMS (PWM Input)
or
Network (RS485)
Refer to paragraph 3.3 for instructions on
changing menu options.
5.6.1 BMS External Field Wiring
Wiring connections for BMS control using PW M
signaling are made between connector JP2 on
the BMS panel (boilers 1 through 8), and the
B.M.S. (PW M) 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) 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 and the boiler end
must be left floating. Each unit’s wiring must
conform to the above.
5.6.2 BMS Setup and Startup
This mode of operation is factory preset and the
AERCO BMS 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 BMS Model 168 can be utilized for
the Combination Mode, not the BMS II
(Model 5R5-384).
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) 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 simul-
tan 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