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Benchmark Platinum-Edge [II]: Operation-Service Manual
SECTION 7
– BOILER SEQUENCING TECHNOLOGY
OMM-
0137_E • GF-211 • 12/13/2019 Technical Support • (800) 526-0288 • Mon-Fri, 8 am - 5 pm EST Page
91
of
153
7.3.2 Option 2 Constant Setpoint: Modbus Wired Header Temp Sensor
OPTION 2
Instructions: Constant Setpoint, Modbus Wired Header Temp Sensor
Step 1: MODBUS HEADER TEMP SENSOR WIRING
– ANY BOILER
1. Connect the
Modbus Transmitter
terminal
Pin B
to the I/O board strip
J3
, terminal
13
(
BST RS485+)
and
Pin A
to terminal
15
(
BST RS485
–
) on any of the Boiler units using
shielded pair 18 - 22 AWG cable.
2. Connect the
Header Temp Sensor
to pins
2
and
3
of the
Modbus Transmitter
units using
shielded pair 18 - 22 AWG cable.
3. Install a jumper wire between pins
1
and
2
of the
Modbus Transmitter
.
NOTES:
•
Polarity must be observed for the RS485 connections.
•
Ground the shield to any
Shield
terminal on the I/O board, such as terminal
3
or
8
.
•
The
Header Temp 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.
•
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.
Continued on next page
MODBUS TRANSMITTER
15 BST RS485
–
HEADER TEMP SENSOR
13 BST RS485+
3 Shield
I/O BOARD STRIP J3