Benchmark 750 – 1000 Boiler User Manual - INTERNATIONAL
CHAPTER 5 – MODE OF OPERATION
OMM-0119_0A
AERCO International, Inc.
•
100 Oritani Dr.
•
Blauvelt, NY 10913
Page
65
of
170
GF-130-I
Ph.: 800-526-0288
11/03
/2016
CHAPTER 5.
MODE OF OPERATION
5.1 INTRODUCTION
The Heating Boiler is capable of being operated in any one of six different modes. The following
sections in this Chapter provide descriptions of each of these operating modes. Each Heating
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 Chapter 3. 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.
5.2.1 Reset Ratio
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.
5.2.2 Building Reference Temperature
This is a temperature from 40°F to 230°F (4.4°C to 110°C). 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 (21.1°C), then at an outside
temperature of 69°F (20.6°C), the supply header temperature will increase by 1.6° to 71.6°F
(0.9°C to 22°C).
5.2.3 Outdoor Air Temperature Sensor Installation
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 shielded from rain and snow. If a cover or shield is used, it must
allow free air circulation. The sensor may be mounted
up to 200 feet (61m)
from the unit.
Sensor connections are made at the Input/Output (I/O) Box on the front of the Heating Boiler.
Connections are made at the terminals labeled
OUTDOOR AIR IN
and
AIR SENSOR COM
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, section 2.8.1 for additional wiring
information.
