AERCO KC1000 Low NOx Boiler July 2011 - Manual (Page 43)

MODE OF OPERATION
5-1
SECTION 5 - MODE OF OPERATION
5.1 INTRODUCTION
The following paragraphs provide detailed
descriptions of the six different modes of
operation for the KC1000 Boiler. Each unit is
shipped from the factory tested and configured
for the ordered mode of operation. All
temperature related parameters are at factory
defaults and work well in most applications.
However, it may be necessary to change certain
parameters to customize the unit to the system.
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 section,
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 it is 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 240°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.
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 from 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 200 feet from
the unit. Sensor connections are made inside
the Input/Output (I/O) Box on the left side of the
KC1000 Boiler. Connections are made at the
terminals labeled OUTDOOR SENSOR IN and
SENSOR COMMON inside the I/O Box using
shielded 18 to 22 AWG wire. A wiring diagram
is provided on the cover of the I/O Box. Refer to
Section 2, paragraph 2.6.2 for additional wiring
information.
5.2.4 INDOOR/OUTDOOR STARTUP
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 temperature and supply header
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).
7. Press the CHANGE key. The display will
begin to flash.
8. Use the ▲ and ▼ arrow keys to select the
desired building reference temperature.
9. Press ENTER to save any changes.
10. Next, scroll through the Configuration Menu
until the display shows Reset Ratio.