Saswell T21HTW-0 User manual

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T21HTW-0
OPERATING
INSTRUCTION

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This manual apply for T21HTW-0, used with 2 Heat / 1 Cool & emergency Heat
Non Programmable, Compatible with heat pump system
SPECIFICATION
Power Supply ………………………20VAC-30VAC 50-60Hz or Battery powered.
Terminal Load…………………………1.0 A per terminal, 3.0A maximum total load
Set point Temperature Range………….45 ºF to 90 ºF (7 ºC to 32 ºC )
Accuracy……………………. +/- 1 ºF or +/- 0.5 ºC .
Dimensions……………………………. 6.0” W X 4.7” H X 1.1” D
Color……………………………………White
FEATURES
Large LCD display with backlight, continuous backlight option.
Simultaneous heat and cool set point storage.
Display of room temperature, set temperature and current time simultaneously.
Fan switch with ON andAUTO functions.
Permanent user setting retention during power loss. No batteries are required.*
Operates from 24VAC, or from 2 size “AA” alkaline batteries.
Air Filter change Indicator.

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Low Battery Indicator.
Temperature calibration.
Batteries required to maintain clock function.
Compressor short cycling protection available
B and O terminals available.
IMPORTANT SAFETY INFORMATION
Always turn off power at the main power source by unscrewing fuse or switching circuit breaker to the off
position before installing, removing, cleaning, or servicing this thermostat.
Read all of the information in this manual before installing this thermostat.
Use a professional contractor to install this thermostat.
This is a 24VAC low-voltage thermostat.
DO NOT INSTALL ON VOLTAGES HIGHER THAN 30 VAC.
All wiring must conform to local and national building and electrical codes and ordinances.
Do not short (jumper) across terminals on the gas valve or at the system control to test
installation. This will damage the thermostat and void the warranty.
Do not switch the system to cool if the temperature is below 50ºF (10ºC).
This may damage the air conditioning system.

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Replace batteries when the battery icon indicates the low battery message.
Change the Air Filter when the Filter Change Icon begins blinking.
Use this thermostat only as described in this manual.
REMOVE THE OLD THERMOSTAT
WARNING ! Electrical Shock Hazard
1. Turn off power at the main service panel by removing the fuse or switching the appropriate
circuit breaker to the OFF position before removing the existing thermostat.
2. Turn off power to the heating and cooling system by removing the fuse or switching the
appropriate circuit breaker off.
3. Remove the cover of the old thermostat. This should expose the wires.
4. Label the existing wires from the existing thermostat before removing.
5. After labeling the wires, remove the wires from the wire terminals.
6. Remove the existing thermostat from the wall.
7. Refer to the following section for instructions on how to install this thermostat.

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INSTALL THE THERMOSTAT
Push the button to open
thermostat front cover
Installing the screws in the base cover
into the junction box and finish wiring
Close the lid then fitting the 2AABattery push up the slide cover
Figure 1

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WARNING ! Electrical Shock Hazard
Turn off power at the main service panel by removing the fuse or switching the appropriate circuit breaker to the OFF
position before removing the existing thermostat.
1. Turn off power to the heating and cooling system by removing the fuse or switching the appropriate circuit breaker
off.
2. Place the system switch (EMER/HEAT/OFF/COOL) in the OFF position.
3. Place the FAN (ON /AUTO) switch in the AUTO position.
4. Gently pull the cover straight off the base. (See figure 1.)
5. Put the thermostat base against the wall where you plan to mount it. (Be sure the wires will feed through the wire
opening in the base of the thermostat.)
6. Mark the placement of the mounting holes.
7. Move the base out of the way. Drill mounting holes. Use a hammer to tap in the supplied anchors into the mounting
holes.
8. Fasten the base loosely to the wall as shown in Figure 1, using two mounting screws. Place a level against the
bottom of the base and adjust until level, then tighten the screws. (Leveling is for appearance only, and will not affect
thermostat operation.)
9. Insert stripped, labeled wires into matching wire terminals. See “Wiring Diagrams”, Figure 2.
CAUTION: Be sure exposed portions of wires do not touch other wires.

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10. Tighten screws on terminal block. Gently tug on each wire to be sure of proper connection.
Double check that each wire is connected to the proper terminal.
CAUTION: Installing batteries backwards can damage the thermostat.
11. Install two fresh “AA” alkaline batteries in the battery compartment. Be sure to match positive (+) ends of batteries
with positive (+) battery terminals in the battery compartment (The thermostat will not operate from 2 size “AA” alkaline
batteries or 24VAC power. When batteries are installed the clock will be maintained during power outages.).
12. Replace the cover on the thermostat by snapping it in place.
13. Turn on power to the system at the main service panel.
14. Test thermostat operation as described in the following section.
Fan operation switch
Read the following information before setting the fan option switch (See figure 3). If you are unsure of your application,
contact a qualified service person.
This thermostat is configured from the factory to energize the fan on a call for heat. If your system is an electric heat or
heat pump that REQUIRES the thermostat to turn on the fan on a call for heat, place the fan option switch in the ELEC
position. If your system does not require the thermostat to energize the fan on a call forheat such asfossil fuel (gas,oil,
etc.), forced air system as well as hydraulic heating systems, place the fan option switch in the GAS position.

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BATTERY OPERATION
With two “AA” batteries installed, your thermostat will maintain time and continuously display the temperature during a
loss of AC power. The LCD Backlight will not function whenAC power is lost.
If the battery icon on the display is flashing, it indicates that the batteries need to be replaced. When the thermostat is
powered only by battery, the battery icon will flash for approximately 2 months before the batteries are expected to
expire.
WIRING DIAGRAM
C
For 24VAC primary
power connect common
side of transformer
to C terminal
,
" " .
Cool relay
Changeover
valve
Emergency
Heat Relay
Auxiliary
Heat Relay
Fan Relay
Power Supply
24V live wire
Equipment
Monitor
Figure 2

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* NOTE:Jumper wire required to use a single Aux Heat for both AUX Heating and Emergency
Heating. NOTE** When presented with 24VAC on the “L” terminal, the Alarm Icon will flash on
the display.
CHECK THERMOSTAT OPERATION
If at any time during testing your system does not operate properly, contact a qualified service person.
Heating system
Turn on power to the system. Fan Operation Move the system switch to the OFF position. If your system does not
have a “G” (Fan) terminal connection, skip to the Heating System.
1.Move the fan switch to the ON position. The blower should begin to operate.
2.Move the fan switch to the AUTO position. The blower should stop immediately.
3.Move the SYSTEM switch to the HEAT position. If the auxiliary heating system has a standing pilot, be sure to
light it.
When the (FA)st heating cycle rate is selected in the configuration menu, (see configuration
menu item 2), the thermostat will call for heat at 0.5ºF (0.5ºC) below set-point, and turn off at set point. When the
(SL)ow heating cycle rate is selected, the thermostat will call for heat at 1.5ºF (1.5ºC) below set-point, and turn off at

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set-point. When the thermostat calls for heat, the display will show Heat On. If the Heat On display is flashing, the
compressor lockout feature is operating in the heat pump mode. (Note: See Configuration menu item 7).
The Aux heating will activate when the room temperature is 2°F (1.0°C) below setpoint temperature.When Aux
heating turns on, AUX 1+2 will be displayed. Note: Aux heating can also be configured to turn on at10ºF below Setpoint
–see the configuration menu 8.
Cooling System
CAUTION: To prevent compressor and/or property damage, if the outdoor temperature is below 50ºF (10ºC), DO
NOT operate the cooling system.
1. Move the SYSTEM switch to the COOL position.
2. When the (FA)st cooling cycle rate is selected in the configuration menu, (see configuration menu item 2), the
thermostat will call for cooling at 0.5ºF (0.5ºC) above set-point, and turn off at set point. When the (SL)ow cool cycle
rate is selected, the thermostat will call for cooling at 1.5ºF (1.5ºC) above set-point, and turn off at set-point. When the
thermostat callsfor cooling, the display will show COOL On. If the COOL On display is flashing, the compressor lockout
feature is operating. (Note: See Configuration menu item 7). If all functions operate properly, the thermostat is
installed correctly.

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Emergency Heating System
EMER by passes the HEAT PUMP to use the heat source connected to terminal E on the thermostat. EMER is
typically used when compressor operation is not desired, or you prefer to use the back-up heating system only.
1. Move the SYSTEM switch to the EMER position. EMER will blink on the display.
2. When the (FA)st heating cycle is selected in the configuration menu, (See configuration menu item 2), the
thermostat will call for Emergency heat at 0.5°F below the set-point, and turn off at set-point. When the (SL)ow heating
cycle is selected, the thermostat will call for Emergency heat at 1.5°F below the set-point, and turn off at set-point.
As the thermostat calls for Emergency heat, the display will show Heat OnAND +2, EMER will display flashing, and
HEAT PUMP will be blank.All these indicate Emergency heating is operating. If all functions operate properly, the
thermostat is properly installed.

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THERMOSTAT LCD DISPLAY
Setting
Temperature
Low Battery indicate
Compressor protection
Timer delay
Fan
On Auto/
Room
Temperature
Mode
Heat Off Cool//
Cooling
Heating
Time setting
Emergency heat
Aux heating
Figure 3

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THERMOSTAT BUTTONS AND SWITCHES
Figure 4
THERMOSTAT OPERATION
1. Setting the thermostat
This thermostat is very easy to operate. Set the SYSTEM switch to either EMER,HEAT or COOL, then press the ▲
or ▼ buttons until the temperature you want to maintain is shown on the right side of the display. If you want to turn the
system off, just move the SYSTEM switch to the OFF position and the FAN switch to the AUTO position.
1 Raises or lowers the temperature setting
2
Selects options in the configuration menu.
3 OFF mode
Hold the down button enter into clock
setting mode
..
.
. :
.
OFF mode:
Fan control
switch (On )/Auto System control switch (EMER /OFF/ )
/ HEAT COOL
User setting reset

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2. Clock setting
Move the SYSTEM switch to the OFF position, then press and hold the ▼buttons for 5 seconds to enter the clock
setting mode. The display will show the HOUR setting first . Use the ▲button to select each user setting. Press the
▼button to shift to the next menu item ( MINUTES,WEEK DAY). Use the ▲button to select each user setting also.
Move the SYSTEM switch to the HEAT or COOL position to exit the setting menu. If no buttons are pressed within
15 seconds , the thermostat will exit the configuration menu.
3. Filter review
Move the SYSTEM switch to the HEAT or COOL position, then press and hold the ▲and ▼buttons for 5
seconds to review filter running days.
To exit the review menu press the ▲or ▼buttons one time. Or If no buttons are pressed within 15 seconds, the
thermostat will exit the configuration menu. In review mode, press and hold the ▲and ▼15 sec. to clean the
filter warning. It will show “dEF”blink.
Troubleshooting
If a voltage spike or static discharge blanks out the display or causes erratic thermostat operation, you can reset the
thermostat by pressing the reset button (See Figure 3). If the thermostat has power, and has been reset and still does
not function correctly, contact your heating/cooling service contractor .

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1. Select cooling cycle rate
The FAsetting is used to produce shorter cooling cycles. The SL setting produces a longer cooling cycle. Both
settings produce very accurate temperature control and can be set to your personal preference. FA cycles the system
at a 0.5ºF (0.5ºC) differential, and SL cycles the system at 1.5ºF (1.5ºC).
2. Select heating cycle rate
The FAsetting is used to produce shorter heating cycles. The SL setting produces a longer heating cycle. Both
settings produce very accurate temperature control and can be set to your personal preference. FA cycles the system
at a 0.5ºF (0.5ºC) differential, and SL cycles the system at 1.5ºF (1.5ºC).
3. Select display backlight
The display backlight improves display contrast inlow lighting conditions. Select 1 for NO backlight display. Select 2
for the backlight to come on for approximately 30 seconds when any button of the thermostat is touched. Select 3 for
the backlight to remain on continuously.
4. Select filter replacement run time
The thermostat will display the FilterAlarm after a set time of operation. This is a reminder to change or clean your
air filter. This time can be set from 0 to 12 months in 1 month increments. Selection of 00 WILL CANCEL THIS
FEATURE.When FilterAlarm is displayed, you can clear it by pressing the ▲ and ▼ buttons. This resets the timer and
starts counting the days until the next filter change.

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5. Select ºF or ºC readout
Changes the display readout to Centigrade or Fahrenheit as required.
6. Select temperature recalibration
This feature allows you to adjust the displayed room temperature up to 4ºhigher or lower. Your thermostat can be
accurately calibrated to match yourprevious thermostat. The current or adjusted room temperature will be displayed on
the display.
7. Select compressor lockout delay 0,1,2,3,4,5
To protect the compressor from short cycling, you can select compressor off-time cycle between 0 to 5 minutes.
When the thermostat compressor time delay occurs, the Cool On or Heat On display will flash during compressor
lockout.
8. Select AU Offset
Allows the user to select the turn on temperature of the Auxiliary Heating system. 2 = 2ºF below set-point,10 = 10ºF
below set-point.

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CONFIGURATION AND OPERATION
The configuration menu allows you to set certain thermostat operating characteristics to your system or personal
requirements. Move the SYSTEM switch to the OFF position, then press and hold the ▲and ▼buttons for 5
seconds to enter the configuration menu. The display will show the first item in the configuration menu. Press the ▼
button to shift to the next menu item. Use the ▲button to select each user setting. To exit the configuration menu and
return to normal operation, move the SYSTEM switch to the HEAT or COOL position. If no buttons are pressed within 2
minutes, the thermostat will exit the configuration menu. The configuration menu chart summaries the configuration
options.An explanation of each option follows.
Step
Press Buttons
Displayed
(Factory
Defaults)
Press ▲
or▼ to
select
Description
1
▲& ▼5
seconds
CC (FA)
FA or SL
Select (FA)st or (SL)ow cooling cycles Default =
FA
2
▼
HC (FA)
FA or SL
Select F(ast) or (S)low Heating cycles. Default
= FA

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3
▼
bL (2)
1 –3
Select display backlight (1) = OFF, (2) = 30
seconds on any button push, (3) = ON. Default
= 2.
Option (3) can be activated only if the common
is used.
4
▼
FL (00)
00, 1 thru12
Select filter time in months. Default = 00.
A selection of “00” deactivates the filter feature.
5
▼
FC (F)
F or C
°F or °C display. Default = F
6
▼
CL (0)
+4 TO -4
Select temperature calibration point up to 4°
higher or 4°lower. Default = 0
7
▼
CP (5)
0 or 5
Compressor Lockout delay. 0 = none, 1=1 Min’;
2=2 Min’; 3=3 Min’, 4=4 Min’, 5=5 Minutes
Default = 5
8
▼
AU (2)
2 or 10
Aux Heat offset , Default=2
2=2º below “Y” on ;10=10º below “Y” on

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CUSTOMER ASSISTANCE
After reading this guide, if you have any question about the operation of your thermostat,please contact
your installer or Energy Utility company or service provider.

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