LAARS SC 12 - Install and Operating Manual - Manual (Page 23)

Page 23 Laars Sequencing Controls
FIRST ON/FIRST OFF ROTATION
• For this type of rotation, dip switch 5 must be in the ON position. ON ON
• On power up, or any time the SC loses power, the Lead Stage will be the fi rst possible stage (as described above).
• The Lead Stage will always be the fi rst stage brought on when there is a call for output.
• As more output is needed, additional stages are added.
• When less output is needed, the Lead Stage will be the fi rst stage turned off. The green light indicating lead stage will then
swit f
in the Sequence 1, 2, and fi nally 3. The lead stage would now be 4 when more output was needed.
OUTPUT CONTROLS
MANUAL OVERRIDES
• Each Stage Output, and the System Output, has an OFF/AUTO/ON switch. OFF/AUTO/ON OFF/AUTO/ON
• The SC only controls units which are switched to AUTO.
• In multistage applications, if any stage of the multistage unit is not switched to AUTO, then the whole unit will not be considered
for automatic Sequencing.
• If a Stage Output is switched ON, then its output relay will always be energized. The Stage Output will run constantly on its ON ON
own internal limits. The System Output or any Pump Output on an SC-6P will also run constantly. This switch position can be
used for testing individual outputs.
• If a Stage Output is switched OFF, then its output relay will not energize. Any Stage Output without an output relay must be OFF OFF
switched to OFF (see chart on pg.17). Also, if a Stage Output needs maintenance or is not working properly, it can be switched OFF OFF
to the OFF position. OFF OFF
OUTPUT LIGHTS
• The row of red lights marked OUTPUT ON indicate which outputs are energized.
• If the red light next to a Stage Output is on, then its output relay should be energized and the output contacts should be
continuous.
• If the red light next to a Stage Output is off, the output relay should not be energized and the output contacts should be open.
EXTERNAL SET POINT
• The SC must have a temperature sensor located in the common header as described on pg. 5.
• A typical use for this option would be to allow an Energy Management System (EMS) to automatically change the Set Point of
the SC to provide an outdoor air reset function for hot water heat.
• Dip switch 6 and 8 must be OFF and dip switch 7 must be OFF OFF ON. This setting will ON ON
allow the SC to read and monitor the system temperature using the temperature
sensor and also to monitor the 4-20mA External Set Point input to change the Set
Point.
• The signal from the EMS must be a 2-wire 4-20mA input (for wiring see pg. 6).
• If the EMS provides a 4mA signal to the SC, the SC Set Point will be 60°F.
• If the EMS provides a 20mA signal to the SC, the SC Set Point will be 220°F.
• The Set Point range is linear between these two point as shown on the side chart.
• When using this option, the Set Point can only be changed by changing the 4-20mA
input. The Set Point display will be shown but it can not be changed by rotating the
knob.
• To disable the SC from the external source, send out a 0mA signal. The Set Point
display will show OFF, and all active Stage Outputs will immediately be turned OFF OFF
off. The System Output (and the individual Pump Outputs on the SC-6P) will remain activated for the period of time set by the
System Delay.
NOTE: The Set Point will read OFF whenever the 4-20mA signal falls below 3.9mA or rises above 20.1mA.
4-20mA Input SC Set Point
4 60°F
6 80°F
8 100°F
10 120°F
12 140°F
14 160°F
16 180°F
18 200°F
20 220°F