Option 2 - Constant Setpoint With Modbus Wired Header Sensor - Aerco BENCHMARK 2500DF User Manual

CHAPTER 10. BOILER SEQUENCING TECHNOLOGY

10.3.2 Option 2 - Constant Setpoint with MODBUS Wired Header Sensor

Step 1: MODbus Header Sensor Wiring
1. Using Shielded pair 18 - 22 AWG cable, connect the Temperature Transmitter (AERCO P/N 65169)
terminal Pin B to the RS485+ terminal on the I/O Box of any of the Boiler units, and Pin A of the
Temperature Transmitter to the RS485- terminal on the I/O Box of any of the Boiler units.
2. Using Shielded pair 18 - 22 AWG cable, connect the Modbus Header Temperature Sensor (AERCO
PN 24410) to pins 2 and 3 of the Temperature Transmitter.
3. Install a jumper wire between pins 1 and 2 of the Temperature Transmitter.
NOTES:
• Polarity must be observed for the RS485 connections.
• The ground for the shield is at the "SHLD" terminal in the I/O the Box.
• The header sensor must be installed between 2 and 10 feet downstream of the LAST boiler in the
plant's supply water header.
• There is no polarity to be observed. The ground for the shield is at the power supply ground. The
sensor end of the shield must be left free and ungrounded.
Temp Sensor PN 24410
Step 2: Configure ALL C-More Units
On ALL Boilers:
1. Go to the Configuration Menu and set the BST Menu item to Enabled.
2. Go to the BST Menu and set the BST Mode item to BST Slave (for now).
On MASTER only:
3. Go to the BST Setpoint item and enter the desired Setpoint.
4. Go to the BST Setup Menu item and set to Enabled.
5. Go to the BST Setpoint Mode item and select Constant Setpoint.
6. Go to the Head Temp Source item and select Network.
7. Go to the Header Temp Addr item and enter the Modbus Address (240).
8. Go to the Header Temp Point item and enter the Modbus Point (14).
When ALL C-More units have been configured:
9. Go to the BST Menu of the desired Master unit and set the BST Mode item to BST MASTER.
Page 128 of 234
05/21/2014
Benchmark 2500DF-3000DF
AERCO International, Inc. • 100 Oritani Dr. • Blauvelt, NY 10913
Phone: 800-526-0288
Modbus Transmitter
OMM-0099_0A
GF-145