Automatic Heating BCM Manuel d'utilisation - Page 4

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Modulex Controller Operation

Figure 1-5. Installing Resistor to Change Default Setpoint

1.4 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 para. 1.4.3). 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 an Energy Management System (EMS)/Building

Automation System (BAS) developed by other manufacturers.

The following subordinate paragraphs 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 Appendix

B of this document.

1.4.1 OPERATING SCENARIO

Each Modulex Boiler is equipped with its own BCM to

allow Modbus Network monitoring and control. The Master

can control the Networked Modulex Boilers utilizing either

Set point

Ext sens

Open

82°C

°C

27°C

Remote Setpoint or Modulation Level signaling.

In the event that the external control signal from the EMS

or BAS is lost, the BCM will assume control of the Modulex

Boilers if enabled by switch. When this occurs, the BCM

will maintain the boiler at a constant setpoint based on

the resistor installed between terminals 6 and 7 of

connector Y2 (see Figure 7-5). If the event occurs and the

2 positions switch is on 0 (disabled), the BCM Fault Relay

will be activated and the red Fault LED (DL2) will light.

1.4.2 PHYSICAL MODBUS RS485 WIRING

Modbus RS485 devices should be wired in a "Daisy-Chain"

configuration similar to the example shown Figure 7-6. DO

NOT wire the units in a "Star" configuration where all devices

are connected to a central point (node).

MASTER

SLAVE

Figure 1-6. Typical Daisy-Chain Modbus/RS485 Network

The physical wiring connections for a Modbus Network should

be made using shielded twisted-pair wire.

Modbus wiring connections are made at terminals 1 and 2 of

BCM connector Y2 as shown in Figure 7-7.

BCM FRONT VIEW

1-7. BCM Modbus (RS485) Connections

SLAVE