Shield Terminals (Shld & Shld); Analog Out Terminals; Rs485 Comm (+, Gnd, & -); Rs232 Comm (Txd & Rxd) - Watts Aerco BENCHMARK 750 User Manual

Benchmark 750 – 1000 Boiler User Manual - INTERNATIONAL
If the Valve Feedback option is used, Shorting Jumper #JP2 on the I/O
Board MUST be inserted.
2.10.7 SHIELD Terminals (SHLD & SHLD)
The SHIELD terminals are used to terminate any shields used on sensor wires connected to the
unit. Shields must only be connected to these terminals.

2.10.8 ANALOG OUT Terminals

The ANALOG OUT terminals (+ & -) output from 0 to 20 mA and may be used to monitor
Setpoint, Outlet Temperature, Valve Position 4-20 mA, Valve Position 0-10v or be set to OFF.
Default setting in the C-More controller is Valve Position 0-10v and settings behave as follows:
1. When 0-10VDC is selected, the voltage output is used by the controller to modulate the
combustion blower via the I/O Box terminals labeled VFD/Blower (Section 2.9.11).
2. If On Board Boiler Sequencing Technology (BST) is enabled, the Analog Output
terminals are used to drive the isolation valve, open and closed. A 0-20 mA signal is
used, with 20 mA to close the valve and 0 to open.
When driving an isolation valve, shorting jumper #JP2 on the I/O
Board MUST be installed.
3. When the 4-20mA is selected for the Analog Output, the 0-10VDC is disabled at the
VFD/Blower terminals, and the selected output is available at the terminals labeled
Analog Output +/-.
2.10.9 RS485 Comm (+, GND, & -)
The RS485 communication terminals are used when the Heating Boiler plant is being controlled
by an Energy Management System (EMS) using Modbus (RS485) communication.
2.10.10 RS232 Comm (TxD & RxD)
As of Firmware version 4.0 and above, these terminals are used only by factory-trained
personnel to monitor OnAER communications via a portable computer.
2.10.11 VFD/Blower (0-10 & AGND)
These terminals (0-10 & AGND) send an analog signal to control the blower speed. When any
of the 4-20mA options is selected for the Analog Outputs (Section 2.9.8), the output from the
VFD/Blower terminals is disabled.

2.10.12 Interlocks

The unit offers two interlock circuits for interfacing with Energy Management Systems and
auxiliary equipment such as pumps or louvers or other accessories. These interlocks are called
the Remote Interlock and Delayed Interlock (REMOTE INTL'K IN and DELAYED INTL'K IN in
Figure 2-12). Both interlocks, described below, are factory wired in the closed position (using
jumpers).
Both the Delayed Interlock and Remote Interlock must be in the
closed position for the unit to fire.
Page 28 of 170
11/03/2016
CHAPTER 2 – INSTALLATION
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AERCO International, Inc. • 100 Oritani Dr. • Blauvelt, NY 10913
Ph.: 800-526-0288
OMM-0119_0A
GF-130-I