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P621U  
SMART TEMP® UNIVERSAL  
5/1/1-DAY PROGRAMMABLE THERMOSTAT  
(FOR BOTH CONVENTIONAL AND HEAT PUMP SYSTEMS)  
INSTALLATION AND OPERATING INSTRUCTIONS  
52161  
IMPORTANT!  
• Please read all of these instructions carefully before beginning  
installation.  
• Label every wire terminal designation on your existing thermostat wiring  
before removing your old thermostat.  
• Ignore the color of the wires since they may not comply with any  
standard. Please connect wires using the terminal letter designations.  
Thank you for your confidence in our product. To obtain the best results from  
your investment, please read and follow the installation procedures carefully, and  
one step at a time. This will save you time and minimize the chance of damaging  
either the thermostat or possibly your heating and cooling system. These  
instructions may contain information beyond that which may be required for your  
particular installation.  
CAUTIONS AND WARNINGS . . . . . . . . . . 2  
SYSTEM COMPATIBILITY . . . . . . . . . . . . 3  
FEATURES . . . . . . . . . . . . . . . . . . . . . . . 4  
TOOLS YOU MAY NEED . . . . . . . . . . . . . . 4  
MOUNTING LOCATION . . . . . . . . . . . . . . 5  
REMOVE OLD THERMOSTAT . . . . . . . . . . 5  
INSTALL THERMOSTAT BASE . . . . . . . . . 6  
WIRING INFORMATION . . . . . . . . . . . . . . 6  
WIRING DIAGRAMS . . . . . . . . . . . . . . . . 8  
HARDWARE SETUP OPTIONS . . . . . . . . 17  
COMPLETE THE INSTALL . . . . . . . . . . . 19  
FRONT PANEL ITEMS . . . . . . . . . . . . . . 19  
OPERATING INSTRUCTIONS . . . . . . . . . 21  
TEMPERATURE PROGRAMS . . . . . . . . . 23  
ADVANCED FEATURES . . . . . . . . . . . . . 24  
BATTERY REPLACEMENT . . . . . . . . . . . 31  
TECHNICAL ASSISTANCE . . . . . . . . . . . 31  
LIMITED WARRANTY . . . . . . . . . . . . . . 32  
MERCURY NOTICE . . . . . . . . . . . . . . . . 32  
WARNING: Use Energizer® or DURACELL® Alkaline Batteries Only.  
Energizer® is a registered trademark of Eveready Battery Company, Inc.  
DURACELL® is a registered trademark of The Procter & Gamble Company  
© 2013 LUX PRODUCTS CORPORATION. ALL RIGHTS RESERVED  
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CAUTIONS AND WARNINGS:  
• This thermostat requires batteries to operate and failure or sub-standard  
performance of the batteries may impair or prevent the correct operation of  
the thermostat. Use Duracell® or Energizer® alkaline batteries ONLY for all  
LUXPRO thermostats requiring batteries. BE SURE TO CHANGE THE BATTERIES  
AT LEAST ONCE A YEAR, or whenever you see the LO BATT indication on the  
screen. Failure to follow these battery instructions could result in property  
damage and/or personal injury.  
• The electrical rating for this thermostat is 1.5 Amps per terminal, with a  
maximum total load of 3.0A for all terminals combined.  
• The thermostat contains parts that may wear out through use and are  
susceptible to failure if over-loaded or used in a manner other than as  
indicated in the documentation.  
• Check unoccupied residences regularly to ensure that all systems are  
operating properly.  
• Check any heating/air-conditioning system including this product before  
operation and at regular intervals.  
• Electrical interference, static electricity, failure or substandard performance of  
batteries, wiring defects in the installation and/or characteristics of the  
connected HVAC devices may prevent the system from regulating heating and  
cooling as anticipated.  
• The thermostat is a sensitive device and dropping the product can cause  
damage to critical components. If the product is dropped or shaken violently  
during transport or installation then it should be replaced immediately.  
• Persons with physical or mental limitations may not be able to promptly  
respond to a malfunction of the heating/air-conditioning system.  
• All residents should be made aware of the potential in any system for  
malfunctions that could cause continuous heating or cooling and should be  
familiar with the operation and location of the heating/cooling appliance on/off  
switch.  
• Read the instruction manual completely before installing the thermostat. You  
should consult a qualified HVAC technician or an electrician if you do not fully  
understand the installation instructions.  
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P621U  
LCD Display Screen  
Fan Mode  
Switch  
Set Slide  
Switch  
FAN  
AUTO  
ON  
T
U
SET  
:
DAY  
5 36  
P
FAN  
RUN  
DAY/TIME  
HEAT  
˚
F
TEMP PROG  
AIR FILTER  
F
FILTER  
72 %LEFT40  
S
ET 74  
TEMPERATURE  
HEAT  
SETBACK  
HOLD  
OFF  
EMER  
COOL  
NEXT  
System Mode  
Switch  
UP / DOWN Buttons  
SYSTEM COMPATIBILITY:  
The electrical rating for this thermostat is 1.5 Amps per terminal, with a  
maximum total combined load of 3.0A for all terminals combined.  
COMPATIBLE WITH:  
• Most 24-volt heating and cooling systems  
• 1 or 2 stage Heat / 1 stage Cool: Gas, Oil or Electric systems  
• 1 or 2 stage Heat / 1 stage Cool: Heat Pump systems  
• 3-wire hydronic (hot water) zone valves  
• Gas Millivolt heaters  
NOT COMPATIBLE WITH:  
• 120/240 VAC line-voltage systems (without a transformer), ask your LUXPRO  
dealer for thermostats to control these systems.  
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FEATURES:  
• 1 or 2-Heat / 1-Cool, 5/1/1-day programming  
• Universal Compatibility for all system types  
• Weekdays, Saturday, and Sunday can be programmed separately  
• Exclusive LUX® Speed SlideTM for easy programming  
• User-selectable periods per day (2 or 4)  
• User-selectable programmable or non-programmable operation  
• LuxLight® EL (Electro-Luminescent) lighted display  
• Programmable air filter life timer  
• Graphical filter monitor  
• Keypad lockout for unauthorized users  
• Manual temperature hold  
• Adjustable vacation hold (1 to 30 days)  
• Temporary temperature override  
• Adjustable temperature differential / cycle-rate  
• Adjustable 2nd heat stage Offset setting  
• User temperature calibration  
• Adjustable heat/cool set temperature limit stops  
• Smart recovery  
• Dual-powered (battery and/or 24-volt system powered)  
• Battery-free memory storage  
• F/C temperature display  
• 12/24-hour clock display  
• 5/2-minute selectable time delay for equipment protection  
TOOLS YOU MAY NEED:  
• Screwdrivers  
• Wire Stripper  
• Wire Cutter  
• Drill with assorted drill bits (new installations only)  
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MOUNTING LOCATION:  
On replacement installations, mount the new thermostat in place of the old one  
unless the conditions listed below suggest otherwise. On new installations,  
please follow these general guidelines:  
1. Mount the thermostat on an inside wall, about 5 ft. (1.5m) above the floor.  
2. Do not locate the thermostat where air circulation is poor such as in a corner,  
alcove, or behind a door that is normally left open.  
3. Do not locate the thermostat where unusual heating or cooling conditions may  
be present, such as: direct sunlight, above a lamp, television, or radiator, or on  
a wall next to an exterior door or window.  
4. Do not locate in a damp environment, as this can lead to corrosion that may  
shorten thermostat life.  
5. If painting or construction work is still ongoing, cover the thermostat  
completely or wait until this work is complete before installation.  
WARNING:  
All wiring must conform to the local codes and ordinances that are in your  
particular location.  
REMOVE OLD THERMOSTAT:  
1. Turn OFF the electricity to all heating and cooling  
components. Do not turn the electricity back on until  
all work is completed.  
2. Remove the front portion of your old thermostat to  
expose the wiring connections.  
F
OF  
3. Write down the letters printed near each wire terminal  
that is used, and also the color of each wire that is  
connected to it. Self-adhesive wire labels are also  
enclosed.  
4. Carefully remove the wires one at a time, and bend them in a manner so that  
they do not fall back inside the wall. Do not allow bare wire ends to touch  
each other.  
5. Loosen the mounting screws for the old thermostat and carefully remove it  
from the wall.  
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INSTALL THERMOSTAT BASE:  
THERMOSTAT TOP VIEW  
1. Strip wire insulation leaving only 3/8 in. (9.5mm) bare wire ends, and clean off  
any corrosion present.  
2. Fill the wall opening with non-combustible insulation to prevent drafts from  
affecting the thermostat’s normal operation.  
3. Separate new thermostat housing using your thumb and index finger. Provide  
pressure in opposite directions to the release tabs on the top of the housing,  
in the directions shown in the diagram shown above.  
4. Route the wires through the opening in the new thermostat base plate, and  
hold the base against the wall. Try to line up the screw holes from the prior  
thermostat, and install the mounting screws.  
5. If the previous holes cannot be used, hold the thermostat base against the  
wall so that it appears straight and level (position the base for best  
appearance) and mark for the new screw holes. Attach the base to the wall  
using the screws provided (use the supplied plastic anchors if needed when  
mounting to a soft material such as drywall).  
WIRING INFORMATION:  
CONNECTING THE WIRES:  
When attaching the wires to the thermostat, please ensure that the bare wire  
ends are held ALL the way into the terminal block while the screw is being  
tightened.  
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WIRING DIAGRAM NOTES:  
(Important, please read all notes before connecting wires)  
• If the information provided in the following wiring diagrams does not clearly  
represent or match your system, please refer to the “TECHNICAL ASSISTANCE”  
section of this manual, and contact us before removing any of your existing  
thermostat wiring.  
• All of the dashed wires shown in the wiring diagrams are either optional, or  
their usage depends upon your specific system type or brand. For example:  
Diagram #1 shows the fan wire as optional. If your system does not have a  
fan, than this terminal will not be used.  
• Terminal letters shown in black represent typical wiring applications.  
Depending upon the brand of your specific system or thermostat, your terminal  
letters may not match exactly. Terminal letters shown in gray represent other  
possible wiring designations that you might see on your existing thermostat  
terminals.  
• The optional “C” terminal is used for powering the thermostat by the 24-volt  
system, using the System Common wire. This can be used alone, or in  
addition to installing batteries as a backup. NOTE: connecting the System  
Common wire to the thermostat is not necessary for heating and cooling to  
function properly.  
• If your old thermostat has both a “Y” and “C” wire both present, then “C” is  
most likely a System Common wire.  
• For Heat Pump systems, you will use either the “O” terminal or the “B”  
terminal on this thermostat, but not both. If your old thermostat has both an  
“O” and a “B” wire present, then “B” is likely a System Common wire and may  
be connected to the “C” terminal. Connecting a System Common wire to this  
thermostat’s “B” terminal may damage the thermostat, and also your heating  
and cooling system.  
• Some Heat Pump systems have a wire for AUX electric heat (usually W2), and  
also a separate wire for Emergency electric heat (usually E). This thermostat  
uses the W2 terminal for both AUX and Emergency Heat. Tape off your “E”  
wire, and confirm that all components function without it.  
• If replacing an old thermostat that has a mechanical clock, there may be two  
wires labeled as “C” for the clock power. Tape off these wires and do not  
connect them to the “C” terminal of this thermostat.  
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WIRING DIAGRAMS:  
DIAGRAM  
SYSTEM TYPE / DESCRIPTION  
PAGE #  
#1  
#2  
#3  
#4  
#5  
#6  
#7  
#8  
CONVENTIONAL:  
CONVENTIONAL:  
CONVENTIONAL:  
CONVENTIONAL:  
CONVENTIONAL:  
CONVENTIONAL:  
HEAT PUMP:  
HEATING ............................................................9  
1-STAGE OR 2-STAGE  
2, 3, 4, 5 WIRES  
HEATING ..........................................................10  
3-WIRE ZONE VALVE  
3, 4 WIRES  
COOLING ..........................................................11  
1-STAGE  
3, 4 WIRES  
HEATING AND COOLING .....................................12  
1-STAGE HEAT  
4, 5 WIRES  
HEATING AND COOLING .....................................13  
2-STAGE HEAT  
5, 6 WIRES  
HEATING AND COOLING .....................................14  
TWO-TRANSFORMERS  
5, 6 WIRES  
HEATING AND COOLING .....................................15  
SINGLE-STAGE ONLY  
4, 5 WIRES  
HEAT PUMP:  
HEATING AND COOLING .....................................16  
WITH AUX / EMERGENCY HEAT  
5, 6 WIRES  
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HARDWARE SETUP OPTIONS:  
On the thermostat’s circuit board, there is a row of DIP switches, labeled #1  
through #8. The position of these switches will change how the thermostat  
operates, and also how information is conveyed to you on the LCD display  
screen. If you make any changes to these options, the changes are not  
recognized unless you either: change the position of the HEAT/OFF/COOL mode  
switch, or press the “HW RST” (Hardware Reset) button on the circuit board. The  
use of this button is further described in the “ADVANCED FEATURES” section of  
this manual.  
These option switches are very small and should be moved carefully using  
objects such as: eyeglass screwdriver, fine-point pen, toothpick, or similar. The  
listing below describes the available choices for each option switch:  
ON  
1
2
3
4
5
6
7
8
SWITCH #1 (SYSTEM): [OFF/DOWN = FURN, default] This setting is used for the  
majority of all heating systems that are not heat pumps. Examples for this  
setting would be: natural gas furnace, hot water baseboard heat, and oil heat.  
[ON/UP = HP] Use this setting if you have a heat pump unit (which looks just like  
an outside air conditioning unit, but is used for both cooing and heating).  
SWITCH #2 (TYPE): [OFF/DOWN = PROG, default] The thermostat controls the  
room temperature by following temperature program periods that you set up  
based upon your daily routine. [ON/UP = MAN] The thermostat operates manually  
just like a mechanical or non-programmable model. This method of operation is  
very basic and only shows the room temperature and set temperature; there are  
no temperature programs, days of the week, or clock times.  
SWITCH #3 (PERIODS): [OFF/DOWN = 4, default] The thermostat uses four  
temperature program periods in both heating and cooling (MORN, DAY, EVE, and  
NITE). Each period has a separate start time and a set temperature. [ON/UP = 2]  
The thermostat operates in the same manner as above, however there are only  
two temperature program periods for heating and cooling (DAY and NITE). This  
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may be more convenient if you are typically home during the day, and only need  
the set temperature to be different while you are sleeping.  
SWITCH #4 (SCALE): [OFF/DOWN = F, default] All temperature values are  
displayed using the Fahrenheit scale. [ON/UP = C] This setting displays all  
temperature values using the Celsius scale.  
SWITCH #5 (TIME): [OFF/DOWN = 12 HR, default] This setting displays the clock  
times and temperature program period start time values on the screen using US  
standard AM and PM values. [ON/UP = 24 HR] This setting displays the clock and  
temperature program period start time values on the screen using the 24 HR  
military-time format (17:30 hours, 22:00 hours, without using AM/PM).  
SWITCH #6 (DELAY): [OFF/DOWN = 5 MIN, default] This sets the minimum length  
of time that Heat or Cool must remain either On or Off, before it will  
automatically switch to the alternate On or Off state. This internal delay prevents  
rapid cycling of your system and provides equipment protection particularly for  
cooling units. The 5-minute setting is fine for most applications. [ON/UP = 2  
MIN] If you feel that your system may need to cycle more frequently than the  
thermostat is allowing, then you may use the 2-minute setting.  
SWITCH #7 (RECOVERY): [OFF/DOWN = DISABLE, default] The Early Recovery  
feature affects how the thermostat transitions from an energy saving setback  
(DAY and NITE) program period, to a comfort (MORN and EVE) program period  
temperature, when it is following the daily temperature programs. When this is  
disabled, the thermostat makes a set temperature change at the beginning of an  
upcoming period's start time. [ON/UP = ENABLE] The Early Recovery feature will  
calculate the capability of your system and turn on the heating or cooling early  
so that the temperature in your home reaches the desired set point as close as  
possible to the start of the period. During the time that the thermostat is  
performing a recovery, the word “RECOV.” will be shown in the display screen.  
SWITCH #8 (BATTERY MONITOR): [OFF/DOWN = ON, default] This setting,  
regularly monitors the battery level, and shows “LOW BAT” on the screen if the  
batteries need to be replaced. Use this setting at all times when batteries are  
present in the thermostat. [ON/UP = OFF] This setting only applies if you are  
NOT physically using batteries in the thermostat, and are powering the  
thermostat entirely from the system (“C” wire terminal).  
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GAS / ELEC SLIDE SWITCH (FAN OPERATION):  
This switch is a physical component by itself on the  
circuit board, and is much larger than the DIP  
switches listed above. [DOWN = GAS, default] This  
setting lets the heating system control the blower  
fan automatically by itself. Systems that would  
typically use the “GAS” setting would be: natural  
gas, propane, or oil furnaces. This setting has no  
effect upon Cool mode operation. [UP = ELEC/HP]  
This setting runs the system’s blower fan when  
BATTERY  
ELEC  
GAS  
heat is called for, and is required for heating systems that do not control their  
own fan while the thermostat is in HEAT mode. Heat pump systems, and units  
with an electric heating element typically require this setting.  
COMPLETE THE INSTALL:  
Once the hardware options are set, install two new Energizer® or DURACELL®  
"AA" size alkaline batteries. Ensure that the batteries are installed in the proper  
direction as per the markings shown in the battery tray. If the batteries were  
already installed before changing the hardware setup options, change the  
position of the HEAT/OFF/COOL System Mode switch to accept the new hardware  
option switch settings.  
FRONT PANEL ITEMS:  
These items below are all located behind the door on the front of the thermostat.  
To open the door, pull outwards using the small indentation in the center of the  
top edge of the thermostat housing.  
HEAT / OFF / COOL, SYSTEM MODE SWITCH: Set this switch to HEAT to control  
your heating system, and COOL to control your cooling system. The OFF position  
will disable both the heating and cooling units.  
AUTO / ON, FAN MODE SWITCH: When this switch is in AUTO, the blower fan (if  
present in your system) will automatically cycle on and off by itself while heating  
or cooling is running. When in the ON position, the blower fan will run constantly  
with or without a demand for heating or cooling, even when the System Mode  
switch is in the OFF position.  
NOTE: The Fan Mode switch only works if your system provides a wire for the  
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thermostat’s “G” wire terminal, to control a blower fan. The Fan Mode switch  
has no effect in systems that do not have a blower fan (such as a hot water  
radiator system).  
MULTI-FUNCTION, SET SLIDE SWITCH: This switch provides an easy way to  
quickly access the most commonly used thermostat settings. This switch has 4  
individual positions, and unless a specific setting is being adjusted, this switch  
should always remain in the RUN position for the thermostat to control the room  
temperature. The other Set Slide switch positions are described in greater detail  
in the ADVANCED FEATURES section. NOTE: this switch is only operable when the  
thermostat is in “Programmable” mode. When the thermostat is used in  
“Manual” control mode, all 4 of the switch positions will act like the RUN  
position, except the “AIR FILTER” position.  
SETBACK BUTTON: This button activates and deactivates the SETBACK feature,  
which overrides the set temperature for an adjustable duration. This feature is  
described in greater detail in the ADVANCED FEATURES section.  
UP / DOWN BUTTONS: The UP and DOWN buttons are used to adjust any item  
that can be changed by the user. Examples are the set temperatures, clock  
times, and days of the week. In many cases, an item may be flashing if it can  
currently be adjusted.  
HOLD BUTTON: This button activates and deactivates the manual Temperature  
Hold feature.  
EMER BUTTON: When in Normal Run mode, the usage of this button varies  
depending upon your specific system configuration. For heat pump systems,  
pressing this button enables your emergency heat function, which is described in  
greater detail in the OPERATING INSTRUCTIONS section. For conventional  
systems, there is no such thing as emergency heat, so this button will have no  
effect.  
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NEXT BUTTON: This button is mostly used while setting items such as software  
options, and temperature program periods. When there are several items on the  
screen that can be changed, usually one of them is flashing indicating that it can  
be adjusted. Pressing the NEXT button will cycle through which item is flashing.  
OPERATING INSTRUCTIONS:  
SET DAY AND TIME: Place the Set Slide Switch into the DAY/TIME position. With  
the day flashing, press UP or DOWN to set the day of the week. Press NEXT and  
the clock time will start flashing. Use UP or DOWN to set the time, making sure  
the AM/PM indication is correct. Holding the UP or DOWN buttons will make the  
clock digits scroll rapidly. Return the Set Slide switch to the RUN position when  
finished.  
HEATING AND COOLING: Basic operation of your heating or cooling system can  
be obtained with the Set Slide Switch in the RUN position and choosing either  
HEAT or COOL on the System Mode switch. The temperature can be adjusted  
using the UP and DOWN buttons. When the thermostat is first powered up, it will  
follow a default temperature routine that is preset from the factory (shown  
below).  
PERIOD  
HEAT MODE  
COOL MODE  
MORN 6:00 AM 70 °F (21 °C) 6:00 AM 78 °F (26 °C)  
DAY  
EVE  
8:00 AM 62 °F (17 °C) 8:00 AM 82 °F (28 °C)  
6:00 PM 70 °F (21 °C) 6:00 PM 78 °F (26 °C)  
NITE 10:00 PM 62 °F (17 °C) 10:00 PM 75 °F (24 °C)  
EMERGENCY HEAT: (Heat Pump Configuration Only). While in normal Heat mode  
with the Set Slide switch in the RUN position, one single press of the EMER  
button will activate Emergency Heat mode. A single press again will end  
Emergency Heat mode, and return back to normal Heat mode. While in  
Emergency Heat mode, the word “EMER” will also be shown in the middle portion  
of the display screen. If a power loss occurs while in Emergency Heat mode, the  
thermostat will continue to remain in Emergency Heat mode even after the power  
comes back on.  
Emergency Heat mode will prevent the first stage of your heat pump system from  
turning on, and use only the “W2” heat terminal (Auxiliary Heat) as the primary  
heating source. This will not only prevent the heat pump from wasting energy if  
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outdoor temperatures are too low to support efficient operation, but it could also  
prevent damage to the heat pump if outside temperatures are below the  
manufacturer’s recommendations. As every heat pump has different operating  
characteristics, you should refer to your heat pump literature to determine when  
to disable the heat pump and run in Emergency Heat mode.  
LCD DISPLAY BACKLIGHT: The display screen is lighted to assist viewing at  
nighttime, or in locations with low light levels. A press of any button on the front  
panel will light the display for approximately 10 seconds. Any button presses  
that occur while the light is on will reset the 10-second timer, causing the screen  
to remain illuminated for an additional 10 seconds.  
TEMPERATURE OVERRIDE: While in Program RUN mode, the set temperature can  
be temporarily changed by pressing UP or DOWN. The set temperature will return  
to the programmed value stored in memory when the start time of the next  
upcoming program period is reached (Morn, Day, Eve, Nite). While a Temporary  
Override is in effect, the word “OVERRIDE” will be shown in the display screen.  
An Override may be cancelled moving the mode switch to OFF, then back to HEAT  
or COOL.  
MINIMUM RUN TIME: The thermostat has a default internal time delay of 5  
minutes between load-on and load-off activations to prevent heating or cooling  
system damage, which can occur from very frequent cycling. If heating or  
cooling does not turn on right away with a manual change in set temperature,  
please wait at least 5 minutes and the system should resume normal operation.  
TEMPERATURE HOLD: A Temperature Hold is used for maintaining a fixed set  
temperature. Once a Hold is initiated, the thermostat will maintain the set  
temperature indefinitely. A Hold may be used for days, weeks, or even months at  
a time, as long as the thermostat has adequate power. To enter Hold mode:  
press the HOLD button one time and the word “HOLD” will appear in the display.  
To cancel a Hold, press the HOLD button one more time. If a complete power  
failure occurs during a Temperature Hold, the thermostat will continue to remain  
in Hold mode even after the power comes back on. NOTE: If you plan to leave  
the thermostat in Hold mode for an extended duration (unattended), it is  
advisable to install new Energizer® or DURACELL® "AA" size alkaline batteries  
prior to leaving to ensure reliable operation of your heating and cooling system.  
STATIC NOTICE: This thermostat is protected against normal static electric  
discharges, however to minimize the risk of damaging the unit in extremely dry  
weather, please touch a grounded metal object before touching your thermostat.  
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TEMPERATURE PROGRAMS:  
By default, this thermostat has 4 separate program periods for both Heat and  
Cool mode, they are: MORN, DAY, EVE, and NITE. Each period ends at the start  
time of the following period. The heat programs are set in HEAT mode, and the  
cool programs are set in COOL mode.  
NOTE: If the thermostat is configured to use only 2 periods per day instead of 4  
(HARDWARE SETUP OPTIONS), the thermostat will only use the DAY and NITE  
periods. The MORN and EVE periods will not be visible on the screen.  
SET TEMPERATURE PROGRAMS: Move the Set Slide switch to the TEMP PROG  
position. Programming will start with all 5 weekdays, Monday through Friday (all  
grouped together). Use the UP/DOWN buttons to adjust the start time for the  
MORN period, then press the NEXT button to advance. Use the UP/DOWN buttons  
to adjust the set temperature for the MORN period, then press the NEXT button to  
advance. Now adjust the start time and set temperature for the DAY period,  
pressing the NEXT button after each to advance. Continue with these same steps  
to adjust the start times and set temperatures for the EVE and NITE program  
periods.  
When the NITE period is finished for the weekdays, the thermostat will advance  
forward to the Saturday program, with the MORN period start time flashing.  
Perform the same steps that you used for setting the weekday periods, pressing  
the NEXT button to advance through each flashing value.  
When the Saturday NITE period is finished, the thermostat will advance forward  
to the Sunday program, with the MORN period start time flashing. Perform the  
same steps that you used for setting the Saturday periods, pressing the NEXT  
button to advance through each flashing value. Return the Set Slide switch to  
the RUN position when you are finished.  
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ADVANCED FEATURES:  
TEMPERATURE SWING AND OFFSET SETTING: A thermostat works by turning  
your heating or cooling system on and off whenever the room temperature varies  
from the desired set-point temperature. The amount of this variation is called  
the swing. Generally your system should cycle on about 3 to 6 times per hour. A  
smaller swing number makes the system cycle more frequently, so the room  
temperature is more precise and constant. A larger swing number will make the  
system remain on for a longer duration each time and decreases the number of  
cycles per hour. There is only one Swing setting, and this determines the cut-in  
and cut-out points for both the first and second stages (if present), in both Heat  
mode and Cool mode.  
NOTE: The Swing and Offset settings need to be performed in a timely manner, as  
the thermostat will timeout and automatically exit these adjustment screens after  
approximately 10 seconds without a button press.  
TO CHANGE THE SWING SETTING: Ensure that the System Mode switch is in the  
OFF position and the Set Slide switch is in the RUN position. Press and hold the  
HOLD button for at least 5 seconds. The words “SET” and “SWING” will appear  
on the screen, along with a single flashing digit. Use the UP/DOWN buttons to  
change the number value between 1 and 9 (0.25F to 2.25F, in 0.25F degree  
increments). Number 1 is the default setting. Press the NEXT button to accept  
the swing setting and proceed to the OFFSET setting.  
TO CHANGE THE OFFSET: After the Swing value has been accepted, the words  
“SET” and “OFFSET” will be shown on the screen, along with a flashing digit.  
This setting is shown as a number of degrees, and is similar in nature to the  
Swing however this only effects the operation of the second (auxiliary) heating  
stage, if present. The setting range for Offset is from 0 to 9 degrees. When set  
to 0 degrees, the second heating stage is completely disabled while in regular  
Heat mode (Emergency Heat mode will still function for heat pump  
configurations). An Offset value from 1 to 9 degrees will determine the number  
of degrees from the set point that will be required for the second heating stage  
to turn on. This setting can be used to conserve energy in situations where the  
second heating stage is more costly to operate when compared to the first stage.  
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Cut-In / Cut-Out  
(1st Stage)  
70˚F Set  
Temperature  
Swing  
Setting=  
#2 (+/- 0.5˚F)  
Offset **  
Setting=  
4˚F degrees  
(2nd Stage) **  
Cut-In / Cut-Out  
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DEGREES (F)  
** = Only applies if a second  
heat stage is present  
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TEMPERATURE CALIBRATION: The internal temperature sensor in this thermostat  
is accurately calibrated at the factory, and in most cases alterations to this  
setting should not be needed. The Temperature Calibration feature allows you to  
manually offset the measured temperature by as much as plus or minus 5°F  
(3°C) degrees from its original value. This feature can be useful to match or  
synchronize this thermostat to another one or more, if multiple thermostats are  
used in the same home.  
NOTE: The Temperature Calibration setting need to be performed in a timely  
manner, as the thermostat will timeout and automatically exit the adjustment  
screen after approximately 10 seconds without a button press.  
TO CHANGE THE TEMPERATURE CALIBRATION: Ensure that the System Mode  
switch is in the OFF position and the Set Slide switch is in the RUN position.  
Press and hold both the UP and DOWN buttons together for at least 5 seconds.  
The words “SET” and “CALwill appear on the screen, along with a single  
flashing temperature digit. Use the UP/DOWN buttons to change the number of  
degrees of adjustment. 0° degrees is the default value, and means no correction  
is being applied. Press the NEXT button to accept the setting.  
SETBACK FEATURE: The setback feature is similar to both a Temperature  
Override and a Temperature Hold, in that both are used to maintain a fixed set  
temperature instead of following a programmed daily routine. A Setback can be  
considered the same as a Temperature Override, which can last for a longer  
duration that you can adjust from 1-12 hours, or 1-30 days. By default, when a  
Setback is activated in Heat mode, the set temperature used will be 5F (3C)  
degrees lower than the current set temp. For Cool mode, the set temperature  
used will be 5F (3C) degrees higher than the current set temp.  
TO START A SETBACK: Ensure that the System Mode switch is in either the Heat  
or Cool position, and that the Set Slider is in the RUN position. Press and hold  
the SETBACK button for at least 2 seconds. The screen will change and show the  
words “HOURS LEFT” and “OVERRIDE”, along with two digits. Use the UP/DOWN  
buttons to set the duration for how long you would like to maintain a fixed set  
temperature (from 1 to 12 hours). If you would like to set the duration for longer  
than 12 hours, keep pressing the UP button. The display will change from  
“HOURS LEFT” to “DAYS LEFT”, with an available duration of 1 to 30 days. Once  
your desired Setback duration is shown on the screen, you can either wait for the  
screen to advance forward on its own, or press the NEXT button (behind the door)  
one time to jump ahead rapidly. Now use the UP/DOWN buttons to select your  
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desired set temperature that will be used for the Setback duration. Just like the  
previous step, you can either wait for the screen to advance on its own, or press  
the NEXT button to advance and return to the Normal Run screen.  
TO CANCEL A SETBACK: While in the Normal Run screen, press and hold the  
SETBACK button for at least 2 seconds. The word “OVERRIDE” will disappear  
from the screen and the Setback will be cancelled. Moving the System Mode  
switch or Set Slide switch, will also cancel a Setback.  
TEMPERATURE LIMIT STOPS: There are two independent set temperature limit  
stops: a maximum heat set temperature, and a minimum cool set temperature.  
These stops do not prevent a user from performing normal actions like  
Temperature Override or Hold. The Heat Limit Stop prevents the set temperature  
from being adjusted higher than the heat limit setting. The Cool Limit Stop  
prevents the set temperature from being adjusted lower than the cool limit  
setting. Each of these temperature stops is user adjustable in one-degree  
increments, and these settings are protected by a selectable 2-digit code to  
prevent unauthorized tampering. By default, this 2-digit code is “00”, and the  
temperature stops can be used as-is with this code.  
NOTE: The Temperature Limit Stop settings need to be performed in a timely  
manner, as the thermostat will timeout and automatically exit the setting screens  
after approximately 10 seconds without a button press.  
TO SET THE HEAT LIMIT STOP: Place the System Mode switch in the OFF position,  
and the Set Slide switch in the RUN position. Press and hold the UP button while  
sliding the System Mode switch from OFF to HEAT. The words “TEMP STOP” and  
“LOCK CODE” will appear on the screen, along with two digits. Use the UP/DOWN  
buttons to select the proper code to access the heat limit setting. Press the  
NEXT button to accept the setting. If the code you tried was not correct, the  
thermostat will exit and return to the Normal Run screen with no changes made.  
If the entered code is correct, the screen will add the word “SET” and display the  
current heat set temperature limit. Use the UP/DOWN buttons to adjust the  
maximum heat set temperature value. Press the NEXT button to accept the  
setting and return to the Normal Run screen in heat mode.  
TO SET THE COOL LIMIT STOP: Place the System Mode switch in the OFF position,  
and the Set Slide switch in the RUN position. Press and hold the DOWN button  
while sliding the System Mode switch from OFF to COOL. The words “TEMP  
STOP” and “LOCK CODE” will appear on the screen, along with two digits. Use  
the UP/DOWN buttons to select the proper code to access the cool limit setting.  
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Press the NEXT button to accept the setting. If the code you tried was not  
correct, the thermostat will exit and return to the Normal Run screen with no  
changes made. If the entered code is correct, the screen will add the word “SET”  
and display the current cool set temperature limit. Use the UP/DOWN buttons to  
adjust the minimum cool set temperature value. Press the NEXT button to accept  
the setting and return to the Normal Run screen in cool mode.  
TO CHANGE THE TEMPERATURE STOP LOCK CODE: Place the System Mode switch  
in the OFF position, and the Set Slide switch in the RUN position. Press and hold  
the NEXT button for at least 5 seconds. The words “TEMP STOP” and “LOCK  
CODE” will appear on the screen, along with two digits. Use the UP/DOWN  
buttons to enter the current code (“00” by default) and press the NEXT button  
one time. The word “SET” will now be displayed. Use the UP/DOWN buttons to  
choose a new 2-digit code between “00” and “99”. Press the NEXT button to  
accept the setting. The screen will flash briefly to confirm the code change, and  
return to the Normal Run screen in Off mode.  
KEYPAD LOCKOUT: You can lock the front panel buttons to prevent unauthorized  
tampering of your thermostat settings.  
NOTE: These keypad lock instructions need to be performed in a timely manner.  
The 4-button sequence which locks the thermostat must be entered within a 10-  
second timeframe, or the keypad lockout sequence will have to be entered again  
from the beginning.  
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GRAPHICAL AIR FILTER MONITOR: In most systems that use a blower fan and air  
ducts, there is an air filter that is either replaceable or requires cleaning. The  
filter is usually located in the air handler, where the blower fan is. This  
thermostat feature assists you with keeping track of proper maintenance and/or  
periodic replacement intervals for your system’s filter.  
The Graphical Filter Monitor displays a visual bar graph in the center of the  
screen, which shows the amount of air filter life remaining (in % percent), since  
the last time the air filter timer has been reset. Each dot in the filter bar graph  
equals 10 percent (example: 4 dots shown means 40 percent filter life  
remaining). This feature is for information purposes only, and does not affect the  
operation of your heating or cooling equipment, or the thermostat. When the  
filter usage duration has completly expired, the vertical filter bar graph will be  
empty, and the word “FILTER” will flash on the screen.  
TO SET THE AIR FILTER DURATION: Move the Set Slide switch to the “AIR FILTER”  
position. The words “SET DAYS” will be shown on the screen, along with the  
word “FILTER” and 2-3 characters at the top right corner of the display. Press  
either of the UP/DOWN buttons to select the desired filter duration (in days) from  
the following choices: OFF, 30, 60, 90, 120, 180, or 365. If the filter duration  
value is set to “OFF”, then the Air Filter Monitor will be completely disabled.  
Return the Set Slide switch to the RUN position when you are finished.  
TO RESET THE FILTER USAGE COUNTER: Move the Set Slide switch to the “AIR  
FILTER” position. The three small digits at the bottom of the screen tell you the  
quantity of filter days remaining. Pressing the NEXT button will toggle the  
display between showing the days remaining as a number, or a graphical  
precentage remaining using the vertical bar graph. Press both the UP and DOWN  
buttons together at the same time, and the usage counter will return to the  
beginning of the value that it originally started counting from. Refer to the  
previous paragraph, should you wish to change the starting value for the filter  
monitor. Return the Set Slide switch to the RUN position when you are finished.  
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HARDWARE RESET: The Hardware Reset button (labeled “HW  
RST”) is a small round push button that is located towards the  
right side if the circuit board, just below the battery holder.  
Pressing this button will cause the LCD display screen to  
become fully populated, the heating and cooling load relays to  
cycle off, read the position of the Hardware Setup Option  
switches, and will perform an internal system check of the thermostat  
HW RST  
components. If your thermostat appears to be acting in an erratic manner,  
pressing the Hardware Reset button may remedy this behavior. The temperature  
programs are not erased when a hardware reset is performed, however the clock  
will have to be changed to match the current day and time.  
SOFTWARE RESET: The Software Reset button (labeled “SW  
RST”) is a small round push button that is located towards the  
left side if the circuit board, just below the battery holder. A  
Software Reset is used to erase all heating and cooling  
SW RST  
temperature programs, and any user-adjustable software  
values such as: Swing, Offset, and Calibration, to their original  
factory default values. To perform a Software Reset, press and hold the Software  
Reset button for at least 5 seconds. The LCD display screen will become fully  
populated, than return to normal. The thermostat will still retain the current day  
and ttime even after a Software Reset has been performed.  
COMPRESSOR PROTECTION BYPASS: This optional feature permits the installer  
or service technician to temporarily disable the built in compressor protection  
delays. This is most useful for diagnosing and testing the heating and cooling  
systems after installation is complete, and should not be used during normal  
operation. To activate this feature, press and hold both the NEXT and HOLD  
buttons, while also perform a single press of the Hardware Reset button (the LCD  
display screen will become fully populated). Continue to hold the NEXT and  
HOLD buttons until the LCD display screen returns to normal. All compressor  
protection delays (in all modes of operation) will be disabled for 5 minutes. After  
the 5-minute duration has expired, the thermostat will return to normal operation  
automatically.  
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BATTERY REPLACEMENT:  
This thermostat is powered by two “AA” Alkaline batteries. The batteries should  
be replaced AT LEAST once per year to ensure reliable operation (or sooner, if the  
“LOW BATT” icon appears at the top of the display screen). The batteries are  
located on the back of the thermostat, at the top of the circuit board. The front  
portion of the thermostat can be removed from the back half by pulling straight  
outwards on the top and bottom of the thermostat housing, at the large  
indentations that are present in the center of the top and bottom edges.  
When installing new batteries, we recommend using only brand new Energizer®  
or DURACELL®, “AA” size alkaline batteries. Please observe the polarity  
markings shown in the battery compartment to ensure proper installation. When  
finished, line up the front of the thermostat to the base, and firmly press together  
to securely latch the front and back halves together properly.  
TECHNICAL ASSISTANCE:  
If you have any problems installing or using this thermostat, please carefully and  
thoroughly review the instruction manual. If you require assistance, please  
contact our Technical Assistance department at 856-234-8803 during regular  
business hours between 8:00AM and 4:30PM Eastern Standard Time, Monday  
through Friday. You can also receive technical assistance online anytime day or  
guides, answers to the most common technical questions, and also permits you  
to email your questions to our technical support staff at your convenience.  
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LIMITED WARRANTY:  
If this unit fails because of defects in materials or workmanship within three  
years of the date of original purchase, LUX will, at its option, repair or replace it.  
This warranty does not cover damage by accident, misuse, or failure to follow  
installation instructions. Implied warranties are limited in duration to three years  
from the date of original purchase. Some states do not allow limitations on how  
long an implied warranty lasts, so the above limitation may not apply to you.  
Please return malfunctioning or defective units to the location from which the  
purchase was made, along with proof of purchase. Please refer to “TECHNICAL  
ASSISTANCE” before returning thermostat. Purchaser assumes all risks and  
liability for incidental and consequential damage resulting from installation and  
use of this unit. Some states do not allow the exclusion of incidental or  
consequential damages, so the above exclusion may not apply to you. This  
warranty gives you specific legal rights and you may also have other rights,  
which vary from state to state. Applicable in the U.S.A. and Canada only.  
MERCURY WARNING AND RECYCLING NOTICE:  
Mercury is considered to be a hazardous material. If this product is replacing a  
thermostat that contains mercury in a sealed tube, contact your local waste  
management authority for instructions regarding recycling and proper disposal.  
It may be unlawful in your state to place it in the trash.  
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T
U
:
DAY  
5 36  
P
FAN  
HEAT  
F
˚
F
FILTER  
72 %LEFT40  
S
ET 74  
SETBACK  
HOLD  
Mt. Laurel, New Jersey 08054, USA  
856-234-8803  
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