INSTALLATION
2-6
2.9.1 Constant Setpoint Mode
GND
NEU
L1
120 VAC, 1 PHASE
The Constant Setpoint Mode is used when it is
desired to have a fixed setpoint that does not
deviate. No wiring connections, other than AC
electrical power connections, are required for
this mode. However, if desired, fault monitoring
or enable/disable interlock wiring can be utilized
(see paragraphs 2.10.9.1 and 2.10.10).
TERMINAL
STRIPS
LOWER RIGHT CORNER
OF FRONT PANEL
Figure 2-8
AC Terminal Block Configurations
2.9 MODES OF OPERATION AND
FIELD CONTROL WIRING
The Benchmark 2.0LN Boiler is available in
several different modes of operation. While
each unit is factory configured and wired for its
intended mode, some additional field wiring may
be required to complete the installation. This
wiring is typically connected to the Input/Output
(I/O) Box located on the lower portion of the unit
front panel (Figure 2-9) behind the removable
front door.
To access the I/O Box terminal strips shown in
Figure 2-9, loosen the four cover screws and
remove the cover. All field wiring is installed
from the rear of the panel by routing the wires
through one of the four bushings provided.
Figure 2-9.
Input/Output (I/O) Box Location
2.9.2 Indoor/Outdoor Reset Mode
Refer to the wiring diagram provided on the
cover of the I/O Box (Figure 2-10) when making
all wiring connections.
This mode of operation increases supply water
temperature as outdoor temperatures decrease.
An outside air temperature sensor (AERCO Part
No. 122790) is required. The sensor MUST BE
wired to the I/O Box wiring terminals (see Figure
2-10). Refer to paragraph 2.10.1 for additional
information on outside air temperature sensor
installation.
Brief descriptions of each mode of operation,
and their wiring requirements, are provided in
the following paragraphs. Additional information
concerning field wiring is provided in paragraphs
2.10.1 through 2.10.10. Refer to Chapter 5 for
detailed information on the available modes of
operation.
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