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Benchmark 2500DF-3000DF Installation, Operation & Maintenance Manual
2.10.3 O
Sensor (O2+ & O2-)
2
The O
SENSOR + and - terminals are used to connect an external oxygen sensor to the I/O box PCB.
2
The O
concentration is displayed in the operating menu of the C-More Control system after a 60 second
2
warm-up period.
2.10.4 Spark Signal (FLW+ & FLW-)
The two SPARK SIGNAL terminals permit an external current sensor to be connected for ignition spark
monitoring purposes. If no spark is present during the ignition sequence, the controller will shut down and
display a fault message.
2.10.5 Analog In (+ & -)
The two ANALOG IN terminals are used when an external signal is used to change the setpoint (Remote
Setpoint Mode) of the boiler.
Either a 4 to 20 mA /1 to 5 VDC or a 0 to 20 mA/ 0 to 5 VDC signal may be used to vary the setpoint or
air/fuel valve position. The factory default setting is for 4 to 20 mA / 1 to 5 VDC, however this may be
changed to 0 to 20 mA / 0 to 5 VDC using the Configuration Menu described in Chapter 3.
If voltage rather than current is selected as the drive signal, a DIP switch must be set on the PMC Board
located inside the C-More Control Box. Contact the AERCO factory for information on setting DIP
switches.
All supplied signals must be floating (ungrounded) signals. Connections between the source and the
boiler's I/O PCB (Figure 2-12) must be made using twisted shielded pair of 18–22 AWG wire such as
Belden 9841. Polarity must be maintained and the shield must be connected only at the source end and
must be left floating (not connected) at the Boiler's I/O PCB.
Whether using voltage or current for the drive signal, they are linearly mapped to a 40°F to 240°F setpoint
or a 0% to 100% air/fuel valve position. No scaling for these signals is provided
2.10.6 B.M.S. (PWM) In (BMS+ & BMS-)
These terminals are only used to connect to legacy AERCO Boiler Management Systems (BMS), which
utilize a 12 millisecond, ON/OFF duty cycle and is Pulse Width Modulated (PWM) to control valve
position. A 0% valve position = a 5% ON pulse and a 100% valve position = a 95% ON pulse. Note that
these connections cannot be used with the AERCO Control System (ACS).
2.10.7 Shield (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 Outputs (+ & -)
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:
•
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 2.12.11).
•
If On Board Boiler Sequencing Technology (BST) is enabled, the Analog Output terminals are
used to drive the isolation valve, open and closed.
•
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 +/-.
Page 28 of 234
05/21/2014
CHAPTER 2 – INSTALLATION
AERCO International, Inc. • 100 Oritani Dr. • Blauvelt, NY 10913
Phone: 800-526-0288
OMM-0099_0A
GF-145
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