AERCO BMK 3.0 LN Nat. Gas APRIL 2009 - Manual (Page 17)

INSTALLATION
2-7
2.9 MODES OF OPERATION AND FIELD
CONTROL WIRING
The Benchmark 3.0 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 2-10) 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 2-11) when making
all wiring connections.
In addition to the terminal strips shown in Figure
2-10, the I/O Box also contains a pre-wired
temperature transmitter which receives inlet air
temperature sensor readings and transmits this
signal to the variable frequency drive (VFD)
contained in the Benchmark 3.0 Boiler. The VFD
utilizes this input signal to adjust the rotation
speed of the blower.
Figure 2-10.
Input/Output (I/O) Box Location
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 2-11. I/O Box Terminal Strip