AERCO BMK 1.5 LN July 2011 - Manual (Page 21)

CHAPTER 2: INSTALLATION
PR2: 05/09/12 Page 21 of 152
Benchmark 1.5LN Low NOx Boiler
Operation and Maintenance Manual
OMM-0041_0D
GF-120
AERCO International, Inc. • 100 Oritani Dr. • Blauvelt, NY 10913 • Ph: 800-526-0288
2.9 MODES OF OPERATION AND FIELD CONTROL WIRING
The Benchmark 1.5 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 2-10, 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.
Refer to the wiring diagram provided on the cover of the I/O Box (Figure 2-10) when making all
wiring connections.
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
2.9.1 through 2.9.9. Refer to Chapter 5 for detailed information on the available modes of
operation.
Figure 2-9: Input/Output (I/O) Box Location
Constant Setpoint Mode 2.9.1
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 2.9.9.1 and 2.9.10).
Indoor/Outdoor Reset Mode 2.9.2
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.