AERCO BMK 1.5 LN Dual Fuel Feb 2013 - Manual (Page 59)

PR2: 05/01/11 Page 59 of 162
Benchmark 1.5LN Dual-Fuel Low NOx Boiler
Operation and Maintenance Manual
OMM-0041_0C
GF-121
AERCO International, Inc. • 100 Oritani Dr. • Blauvelt, NY 10913 • Ph: 800-526-0288
CHAPTER 5: MODE OF OPERATION
5.1 INTRODUCTION
The boiler is capable of being operated in any one of six different modes. The following
paragraphs in this Chapter provide descriptions of each of these operating modes. Each
boiler is shipped from the factory tested and configured for the ordered mode of operation.
All temperature related parameters are at their factory default values which work well in
most applications. However, it may be necessary to change certain parameters to
customize the unit to the system environment. A complete listing and descriptions of the
temperature related parameters are included in Appendix A. Factory defaults are listed in
Appendix E. After reading this chapter, parameters can be customized to suit the needs of
the specific application.
5.2 INDOOR/OUTDOOR RESET MODE
This mode of operation is based on outside air temperatures. As the outside air
temperature decreases, the supply header temperature will increase and vice versa. For
this mode, it is necessary to install an outside air sensor as well as select a building
reference temperature and a reset ratio.
Reset Ratio 5.2.1
Reset ratio is an adjustable number from 0.1 to 9.9. Once adjusted, the supply header
temperature will increase by that number for each degree that the outside air temperature
decreases. For instance, if a reset ratio of 1.6 is used, for each degree that outside air
temperature decreases the supply header temperature will increase by 1.6 degrees.
Building Reference Temperature 5.2.2
This is a temperature from 40°F to 230°F. Once selected, it is the temperature that the
system references to begin increasing its temperature. For instance, if a reset ratio of 1.6 is
used, and we select a building reference temperature of 70°F, then at an outside
temperature of 69°F, the supply header temperature will increase by 1.6° to 71.6°F.
Outdoor Air Temperature Sensor Installation 5.2.3
The outdoor air temperature sensor must be mounted on the North side of the building in an
area where the average outside air temperature is expected. The sensor must be shielded
from the sun's direct rays, as well as direct impingement by the elements. If a cover or
shield is used, it must allow free air circulation. The sensor may be mounted up to two
hundred feet from the unit. Sensor connections are made at the Input/Output (I/O) Box on
the front of the boiler. Connections are made at the terminals labeled OUTDOOR SENSOR
IN and SENSOR COMMON inside the I/O Box. Use shielded 18 to 22 AWG wire for
connections. A wiring diagram is provided on the cover of the I/O Box. Refer to Chapter 2,
paragraph 2.9.1 for additional wiring information.
Indoor/ Outdoor Startup 5.2.4
Startup in the Indoor/Outdoor Reset Mode is accomplished as follows:
1. Refer to the Indoor/Outdoor reset ratio charts in Appendix D.
2. Choose the chart corresponding to the desired Building Reference Temperature.
3. Go down the left column of the chart to the coldest design outdoor air temperature
expected in your area.