Benchmark 750-3000 Installation & Startup Manual
SECTION 6
– BOILER SEQUENCING TECHNOLOGY
OMM-115_D
•
GF-200
•
5/9/2019
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6.3.4 OPTION 4 - OUTDOOR RESET WITH MODBUS HEADER SENSOR
AND MODBUS OUTDOOR SENSOR
OPTION 4 - Outdoor Reset With Modbus Header Sensor And Modbus
Outdoor Sensor Instructions
NOTE:
Both Header Sensor AND Outdoor Sensor must be wired. See the
C-More Controller User
Manual
, OMM-0032 (GF-112) and
ProtoNode User Manual
, OMM-0080 (GF-129) for more
information.
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 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
(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 boiler in the plant’s supply water header.
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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.
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 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
(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.
(Continued)
Temp Sensor P/N
24410
Modbus Transmitter I/O Box
