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

Page 12 LAARS Heating Systems
OUTDOOR RESET WITH NORMAL SEQUENCING
Dip Switch 6 and 7 - OFF and 8 - ON
Press SELECT
Button
DISPLAY Press and hold either the UP or DOWN button to adjust
Once♦
Calculated
This is the water temperature the SC will stage outputs to hold. It is based on outdoor temperature,
Reset Ratio, and the Offset value. If OFF is shown, there is no call for heat. If
PrF is shown, the SC
is waiting for a Prove signal before activating stages.
Twice♦
Outdoor Temp
This is the outdoor sensor temperature value.
3 Times
Outdoor Cutoff
When the outdoor temperature falls below the Outdoor Cutoff value, the SC will give heat. When the
outdoor temperature is above the Outdoor Cutoff, the Calculated value will be OFF and no stages will
be activated except on a DHW call. The Outdoor Cutoff can be set ON or OFF and from 40 to 100°F.
Default is 60°F.
4 Times
Reset Ratio
The Reset Ratio controls the amount of heat which enters the heating system based on the outdoor
temperature. A higher numbered Reset Ratio will result in a higher Calculated water temperature.
See the chart on pg. 19 for the reset curves. The Reset Ratio is adjustable from 1 to 12. Default is 7.
5 Times
Offset
The Offset moves the reset curves vertically up or down. For example, changing the offset from 0 to
-10 will decrease the water temperature 10°F regardless of outdoor temperature or the reset curve
selected. The Offset is adjustable from -40°F to 40°F. Default is 0°F.
6 Times
Reaction Time
The Reaction Time controls the minimum run time for a stage (1/2 the Reaction Time). Also, it con-
trols how long should a stage run before it activates/subtracts another stage. It is adjustable from half
a minute (0.5) to 8.0 minutes. Default is 2 minutes.
7 Times
System Delay
The System Delay controls how long the System relay will remain energized after the last Output has
been turned off or the outdoor temperature rises above the Starter. The System Delay is adjustable
from 0 to 30 minutes.
8 Times
Purge Time
The Purge Time should be set to the length of the unit’s purge cycle. The Purge Time will apply
when any ON/OFF unit is activated. On multiple stage units, the Purge Time will only apply to the Lo
stages. The Purge Time is adjustable from 0.0 to 10.0 minutes. Default is 0.
9 Times
Boiler runtime
This is the minimum amount of time any boiler will run after the Purge cycle has been completed. This
timer does not apply when only one stage is running, the Last Stage Hold
LSH applies in that case.
The Boiler Runtime is adjustable between 0 to 60 minutes. Default is 0.
10 Times
Last Stage Hold
To prevent short cycling of the last stage in low load conditions, the system temperature can exceed
the Calculated water Temperature by the amount selected by the Last Stage Hold before the last
stage is turned off. The Last Stage Hold is adjustable between 0°F to 20°F. Default is 10°F.
11 Times
Setback
The Setback adjusts the number of degrees the Set Point water temperature will be reduced when
Input terminals 7 and 8 are closed. If the Setback is set to 0, then the system will Shutdown on a
closure. The Setback is adjustable from 0°F to 40°F. Default is 0°F.
12 Times♦♦
DHW Priority Time
Only available when the System Output is set to System Pump (dip switch 1 is ON and dip switch 6 is
OFF ) This setting adjusts the amount of time the System relay output will remain off during a DHW
call. If the DHW call is not satisfi ed before the DHW priority time has elapsed, the System relay will
energize to provide heat. The DHW Priority is adjustable from 0 to 4 hours in half hour increments.
Default is 0.
12 to 13 Times♦
Default
The SC returns to the default display of system water temperature.
♦ Actual temperature values are not adjustable
♦♦ May not be available, depending on status of the outdoor sensor and dip switches.