Option 2 - Constant Setpoint With Modbus Wired Header Sensor - Watts Aerco BENCHMARK 750 User Manual

Benchmark 750 – 1000 Boiler User Manual - INTERNATIONAL
CHAPTER 9. BOILER SEQUENCING TECHNOLOGY

9.3.2 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 (P/N 65169) terminal
Pin B to the RS485+ terminal on the I/O Box of any of the units, and Pin A of the Temperature
Transmitter to the RS485- terminal on the I/O Box of any of the units.
2. Using Shielded pair 18 - 22 AWG cable, connect the Modbus Header Temperature Sensor (P/N
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 (0.61 and 3.1m) downstream of the
LAST Heating 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 P/N 24410
Step 2: Configure ALL C-More Units
On ALL Heating Boilers:
1. Go to the Configuration menu item and set the BST Menu item to Enabled.
2. Go to the Boiler Sequencing Menu item 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 Boiler Sequencing Menu item of the desired Master unit and set the BST Mode item to
BST MASTER.
OMM-0119_0A
GF-130-I
Modbus Transmitter
AERCO International, Inc. • 100 Oritani Dr. • Blauvelt, NY 10913
Ph.: 800-526-0288
I/O Box
Page 117 of 170
11/03/2016