Option 4 - Outdoor Reset With Modbus Header Sensor And Modbus Outdoor Sensor - Watts Aerco BENCHMARK 750 User Manual

Benchmark 750 – 1000 Boiler User Manual - INTERNATIONAL
CHAPTER 9. BOILER SEQUENCING TECHNOLOGY
9.3.4 Option 4 - Outdoor Reset with MODBUS Header Sensor AND MODBUS
Outdoor Sensor
NOTE: Both Header Sensor AND Outdoor Sensor must be wired.
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 - Modbus Outdoor Sensor Wiring
1. If you have not already done so when installing the Modbus Header Sensor, use Shielded pair 18 - 22
AWG cable to connect the Temperature Transmitter terminal Pin B to the RS485+ terminal on the I/O
Box of any of the Heating Boiler 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.
•
When mounting the Outdoor sensor, it must be located on the North side of the building where an
average outside air temperature is expected. The sensor must be shielded from direct sunlight as
well as rain and snow. The outdoor sensor may be wired up to 200 feet (61m) from the Heating
Boiler.
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11/03/2016
Modbus Transmitter
AERCO International, Inc. • 100 Oritani Dr. • Blauvelt, NY 10913
Ph.: 800-526-0288
I/O Box
OMM-0119_0A
GF-130-I