MODE OF OPERATION
5-1
Chapter 5 - MODE OF OPERATION
The following is a detailed description of the 6
different modes of operation for the Benchmark
Boiler. Each unit is shipped from the factory
tested and configured in the mode of operation it
was ordered. 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 description
of the temperature related parameters is located
in Appendix A. Factory defaults are located in
Appendix E. After reading this section,
parameters can be customized to suit the needs
of the application.
5.1 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.
5.1.1 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.
5.1.2. BUILDING REFERENCE
TEMPERATURE
This is a number from zero to 300 and once
chosen, 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 choose a building reference temperature of
70 degrees, then at 69 degrees outside
temperature, the supply header temperature will
increase by 1.6 degrees to 71.6 degrees.
5.1.3 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 and is connected to the unit at
the control wiring terminal strip located at the
bottom left hand corner of the control panel.
Connections are to be made to terminals 13 and
14 using a shielded wire of 18 to 22 AWG. For
further wiring outside air sensor wiring details
see section 2.6.2.
5.1.4 INDOOR/ OUTDOOR STARTUP
1. Refer to the indoor/outdoor reset ratio charts
in Appendix D.
2. Choose the building reference temperature.
3. Go down the left column of the chart to the
coldest design outdoor air temperature.
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 three.
5. Now go up that column to the reset ratio row
to find the reset ratio.
6. Access the secondary menu of the
temperature controller and scroll through it
until the display shows REFT. This is the
building reference temperature.
7. Use the
⇑
and
⇓
arrow keys to set the
desired building reference temperature.
8. Press ENTER to accept any changes.
9. Now scroll through the secondary menu until
it displays RR. This is the reset ratio.
10. Use the
⇑
and
⇓
arrow keys to set the
desired reset ratio.
11. Press ENTER to accept the change.
The unit is now ready to run. Return to the
primary menu and start the unit (see section
3.3.4 for instructions on menu changing).
Summary of Contents for Benchmark G-00-711
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