AERCO Modulex E8 Controller (and BCM) For Modulex EXT Boilers - Manual (Page 82)

E8 Controller and BCM for Modulex EXT
Installation, Operation & Maintenance Manual
CHAPTER 8: BOILER COMMUNICATION MODULE (BCM)
Page 82 of 108 AERCO International, Inc. • 100 Oritani Dr. • Blauvelt, NY 10913 OMM-0093_0A
PRI: 06/24/2013 Phone: 800-526-0288 GF-136-C
Figure 8-5: Installing Resistor to Change Default Setpoint
8.4 BCM Configured as Primary Controller Utilizing Modbus
The BCM can be configured as the Primary Controller, instead of the E8, when it is connected
to a Modbus Network. However, the E8 must be disconnected from the e-Bus connection on
the BCM Board (see Section 8.4.3). All Modbus Networks are implemented utilizing a “Master –
Slave” scenario where only one device, the “Master”, can initiate a communication sequence.
However, BCMs can only function as “Slave” devices on a Modbus Network. Therefore, the
BCM must be interfaced to an external controlling “Master”. The “Master” can be AERCO’s
Boiler Management System II (BMS II), AERCO Control System (ACS), or an Energy
Management System (EMS)/Building Automation System (BAS) developed by other
manufacturers.
The following subordinate sections provide descriptions of Modbus Network operation and
required wiring connections between the BCM “Slaves and the controlling “Master” (EMS, BAS).
Detailed information on the Modbus Function Codes, Input/Holding Register Assignments and
other Modbus requirements supported by the BCM are provided in Chapter 9 of this document.
8.4.1 Operating Scenario
An EMS or BAS Master can control the Networked Modulex Boilers utilizing Remote Setpoint.
An AERCO BMS II Master can control the networked Modulex boilers utilizing a Modbus signal.
In the event that the external control signal from the Master BMS II or ACS, EMS, or BAS is lost,
the BCM will assume control of the Modulex Boilers, if enabled. When this occurs, the BCM will
maintain the boiler at a constant setpoint based on the resistor installed between terminals 6