OPERATION SEQUENCE:
When the room temperature is 1.5 degrees below setpoint the thermostat will close the R to W contacts on the
actuator board and signal the SC-Z20 panel that there is a heating call.
When the room temperature is 1.5 degrees above the setpoint the thermostat will close the R to Y contacts on
the actuator board and signal the SC-Z20 panel that there is a cooling call.
DAMPER NOTES:
To balance the HVAC system, unlock the thermostat by setting slide switch 1 to the OFF position. Press and
hold the SETUP key until the word DAMPER appears on the LCD. Press the UP or DOWN key until the word
OPEN appears on the LCD and then press the ENTER key. The damper will drive open. After balancing, the
thermostat must be set for normal damper operation. Using the above steps, press the UP or DOWN key until
only the word DAMPER appears on the LCD and then press the ENTER key.
The actuator board is located on the side of the damper actuator and is wired at the factory.
Each zone damper requires 2VA.
The space thermostat will control up to 12 damper actuators wired in parallel.
If the discharge air temperature at the damper is warmer than 72 degrees, the damper will open on a call for
heating..
If the discharge air temperature at the damper is below 72 degrees, the zone damper will open on a call for
cooling.
SC-Z20 PANEL NOTES:
Use standard 18 gauge thermostat wire.
Run four wire cable from the panel terminals (R, C, Y, W) to each individual zone damper actuator board.
Panel requires a separate 24VAC transformer with proper VA rating.
Locate discharge air sensor 3 feet down stream in trunk line.
Time Delay Speed Up Button shortens all the time delays on the control panel (use for testing only).
Minimum Call Selector Switches determine the number of zones that must be calling in order for the system to
bring on the heating or cooling equipment.
Time clock contacts are closed during occupied cycle.
SC-Z20-T MODULATING OR TWO-POSITION
ZONE THERMOSTAT
PO
PC
W
R
C
DS
DS
Y
1
2
3
4
5
6
7
8
C
R
R
Y
W
1
2
3
4
5
ACTUATOR
BOARD
DAMPER OR
DIFFUSER
ACTUATOR
90 SECOND TIMING
90° STROKE
44 lb.-
in.
2
VA
DAMPER OPEN
(24VAC)
DAMPER CLOSED
(24VAC)
CALL FOR HEAT
(24VAC)
24VAC POWER
(HOT)
24VAC POWER
(COM.)
DUCT SENSOR
DUCT SENSOR
CALL FOR COOL
(24VAC)
(10K OHMS @77°)
OPEN
CLOSED
COM.
DS
DS
HEAT
COOL
WIRE TO
OPTIONAL
SLAVE
DAMPER
(UP TO 12 MAY BE WIRED
IN PARALLEL)
SC-Z20-T
AUTO CHANGEOVER
SPACE THERMOSTAT
R TO W CONTACTS CLOSE
ON A CALL FOR HEAT.
R TO Y CONTACTS CLOSE
ON A CALL FOR COOL
C R
Y
W
WIRE TO SC-Z20
ZONE PANEL TERMINALS
FACTORY JUMPER
RED LED
INDICATES
A CALL FOR
HEATING
GREEN LED
INDICATES
A CALL FOR
COOLING
DUCT SENSOR
COM
OPEN
CLOSE