Table of Contents
Advertisement
5.1 INTRODUCTION
The Benchmark 2.0 Low NOx 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 unit 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
temperature related parameters are included in
Appendix A. The factory defaults are listed in
Appendix
E.
After
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,
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
temperature
decreases
temperature will increase by 1.6 degrees.
5.2.2 Building Reference Temperature
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.
CHAPTER 5
MODE OF OPERATION
descriptions
of
the
reading
this
chapter,
the
supply
header
that
outside
air
the
supply header
MODE OF OPERATION
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 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 Benchmark Boilr. Connections are made
at the terminals labeled OUTDOOR SENSOR IN
and SENSOR COMMON inside the I/O Box.
Use
shielded
18
to
connections. A wiring diagram is provided on
the cover of the I/O Box. Refer to Chapter 2,
paragraph 2.7.1 for additional wiring information.
5.2.4 Indoor/ Outdoor Startup
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.
NOTE
A design engineer typically provides
design
outdoor
air
header
supply
temperature data
4. Once the design outdoor air temperature is
chosen, go across the chart to the desired
supply header temperature for the design
temperature chosen in step 3.
5. Next, go up that column to the Reset Ratio
row to find the corresponding reset ratio.
6. Access the Configuration Menu and scroll
through it until the display shows Bldg Ref
Temp. (Building Reference Temperature).
22
AWG
wire
for
temperature
and
5-1
Advertisement
Table of Contents
