Benchmark 2500 - 3000 Boilers
CHAPTER 2 – INSTALLATION
Page
28
of
204
AERCO International, Inc.
•
100 Oritani Dr.
•
Blauvelt, NY 10913
OMM-0094_0E
03/20/2014
Ph.: 800-526-0288
GF-137
provided in APPENDIX C. This sensor is an active part of the combustion control system and
must be operational for accurate air/fuel mixing control.
2.10.3 O
2
SENSOR
(O2+ & O2-)
The O
2
SENSOR (+) and O
2
SENSOR (–) terminals are used to connect an external oxygen
sensor to the I/O Box PCB. The O
2
concentration is displayed in the operating menu of the C-
More Control system after a 60 second 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 set-
point 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 Output (+ & -)
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 2.10.11).
•
If On Board Boiler Sequencing Technology (BST) is enabled, the Analog Output
terminals are used to drive the isolation valve, open and closed.
