Benchmark 2500 - 3000 Boilers
CHAPTER 2 – INSTALLATION
OMM-0094_0E
AERCO International, Inc.
•
100 Oritani Dr.
•
Blauvelt, NY 10913
Page
29
of
204
GF-137
Ph.: 800-526-0288
03/20/2014
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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 /-.
2.10.9 RS-485 Comm (+, GND, & -)
The RS-485 communication terminals are used when the boiler plant is being controlled by an
Energy Management System (EMS) or an AERCO Control System (ACS) using Modbus (RS-
485) communication.
2.10.10 RS-232 Comm (TxD & RxD)
The RS-232 communication terminals permit a laptop computer or other suitable terminal to be
connected to the boiler. The RS-232 communication feature permits viewing or changing of
Control Panel menu options and also provides access to data logs showing fault and sensor log
displays.
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 2.10.8), 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).
NOTE
Both the Delayed Interlock and Remote Interlock must be in the
closed position for the unit to fire.
2.10.12.1
Remote Interlock In (OUT & IN)
The remote interlock circuit is provided to remotely start (enable) and stop (disable) the unit
if desired. The circuit is 24 VAC and comes factory pre-wired closed (jumped).
2.10.12.2
Delayed Interlock In (OUT & IN)
The Delayed Interlock terminals can be used in one of two ways:
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In conjunction with the optional external sequencing valve (see section 2.14 and
Chapter 10 – BST), a component of AERCO’s on-board Boiler Sequencing
Technology (BST) solution. By default a cable of the boiler’s wiring harness is
connected to these terminals. If BST is implemented, the other end of that cable is
connected to the sequencing valve.
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If BST is
NOT
implemented, the second use is typically in conjunction with the
AUXILIARY RELAY CONTACTS described in section 2.10.14. This interlock circuit
is located in the purge section of the start string. It can be connected to the proving
device (end switch, flow switch etc.) of an auxiliary piece of equipment started by
the unit’s auxiliary relay. If the delayed interlock is connected to a proving device
that requires time to close (make), a time delay (AUX START ON DLY) that holds
the start sequence of the unit long enough for a proving switch to make (close) can
be programmed.
