LAARS SC 12 - Install and Operating Manual - Manual (Page 18)

Page 18 LAARS Heating Systems
OPERATION
SET POINT CONTROL SETTINGS
SET POINT ( SP ) Default: 70°F
• The Set Point is the temperature value the SC will use to control the system.
• The SC will either add Stage Outputs, subtract Stage Outputs, or maintain the same number of Stage Outputs to hold the system
temperature around the Set Point.
• The Set Point is the average temperature the SC will maintain. The size of the fl uctuation above and below the Set Point
depends on the number of stages, the size of each stage, the system load, and the Sequencing mode.
• When controlling temperature, the Set Point can be adjusted to any value in the temperature range.
• If the Set Point value is fl ashing, this indicates that the selected Set Point has been automatically changed. This may occur
because of the Setback setting (see pg. 24) or the DHW mode (see pg. 25).
• If the Set Point displays OFF then the Outdoor Cutoff or the Shutdown is active (see below and pg. 24).
• If it is a temperature system and the External Set Point is being used, the Set Point will vary with the 4-20mA input (see pg. 23).
Pushing the UP or UP UP DOWN buttons while the Set Point is being displayed will not change the value of the Set Point. DOWN DOWN
OUTDOOR TEMPERATURE (OUt) No Adjustment - Display Only
• Use of the Outdoor Sensor is optional in the Set Point operation mode.
• If an Outdoor sensor is installed, it can be used to provide an Outdoor Cutoff (see below).
• If a sensor is not installed, the display will show OPn, indicating that the OUTDOOR terminals are open. In this case, the SC
will control the system to maintain the Set Point temperature.
OUTDOOR CUTOFF (COF) Default: 60°F
• The Outdoor Cutoff sets at what outdoor temperature the SC will begin heating. This setting will only be available if the SC does
not register a fault from the Outdoor sensor (OPn Open or SHt short).
• For heating, when the Outdoor temperature drops below the Outdoor Cutoff temperature, the SC will begin to Sequence stages
for heat. It will continue to Sequence until the Outdoor temperature rises to 2°F above the Outdoor Cutoff temperature.
• The Outdoor Cutoff temperature can be set from 40 to 100°F. In addition, an ON setting is provided to override the Outdoor
Cutoff for continuous Sequencing, and an OFF setting can be used to temporarily prevent any Sequencing.
• The Outdoor Cutoff has a built in 2°F differential.
• If the Outdoor temperature rises 2°F above the Outdoor Cutoff, the SC will not activate stages and the Set Point will read OFF,
unless there is a DHW call.
PROGRAMMED OFFSET (PO) Default: 0°F
External Set Point
• The Programmed Offset can be used to fi ne tune the External Set Point reading.
• A 4mA input signal should generate a Set Point display of 60°F (see pg. 23).
• If a 4mA input generates a display of 62°F, then by setting the Programmed Offset to -2, the display will show 60°F. Similarly, if
a 4mA input generates a display of 59°F then by setting the Programmed Offset to 1, the display will show 60°F.
• The Programmed Offset should only be used to fi ne tune the Set Point display when inputting a 4mA signal. Do not use it to
adjust the Set Point reading at any other mA input value.
• The Programmed Offset can be set from -15 to 15 degrees.
SETBACK/SHUTDOWN (Stb) Default: 0°F
• For temperature applications, the terminals 7 and 77 8 can be programmed to provide either a lower Set Point temperature in
heating or Shutdown.
• T
are sleeping.
• To program INPUT terminals INPUT INPUT 7 and 7 7 8 to Shutdown, set the Setback/Shutdown value to 0. When the SC is Shutdown, the Set
Point display will show OFF.
• The Setback/Shutdown value can also be set from 1 to 40°F.
• For a nonzero value in heating, the Set Point will be reduced by the amount of the Setback. This will be indicated by the System
Temperature display fl ashing and the Set Point display fl ashing the new value.