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P521U  
SMART TEMP® UNIVERSAL  
5/2-DAY PROGRAMMABLE THERMOSTAT  
(FOR BOTH CONVENTIONAL AND HEAT PUMP SYSTEMS)  
INSTALLATION AND OPERATING INSTRUCTIONS  
52126  
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.  
SYSTEM COMPATIBILITY. . . . . . . . 2  
FEATURES . . . . . . . . . . . . . . . . . 3  
TOOLS YOU MAY NEED . . . . . . . . . 3  
MOUNTING LOCATION . . . . . . . . . 4  
REMOVE OLD THERMOSTAT . . . . . 4  
INSTALL THERMOSTAT BASE. . . . . 5  
WIRING INFORMATION . . . . . . . . . 5  
CAUTIONS AND WARNINGS. . . . . . 6  
WIRING DIAGRAMS . . . . . . . . . . . 8  
HARDWARE SETUP OPTIONS. . . . 17  
COMPLETE THE INSTALL. . . . . . . 19  
FRONT PANEL ITEMS . . . . . . . . . 20  
OPERATING INSTRUCTIONS. . . . . 21  
TEMPERATURE PROGRAMS. . . . . 24  
ADVANCED FEATURES . . . . . . . . 25  
BATTERY REPLACEMENT. . . . . . . 32  
TECHNICAL ASSISTANCE. . . . . . . 33  
LIMITED WARRANTY . . . . . . . . . 33  
MERCURY NOTICE . . . . . . . . . . . 33  
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 Gillette Company, Inc.  
© 2012 LUX PRODUCTS CORPORATION. ALL RIGHTS RESERVED  
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P521U  
LCD Display Screen  
Fan Mode  
Switch  
Set Slide  
Switch  
FAN  
AUTO  
ON  
T
U
SET  
:
DAY  
5 36  
P
RUN  
DAY/TIME  
FAN  
HEAT  
˚
F
TEMP PROG  
AIR FILTER  
˚
72  
ROOM  
S
ET 74  
TEMPERATURE  
HEAT  
HOLD  
OFF  
EMER  
COOL  
NEXT  
System Mode  
Switch  
UP, DOWN and HOLD 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:  
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•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
1 or 2-Heat / 1-Cool, 5/2-day programming  
Universal Compatibility for all system types  
Weekdays and Weekends 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  
Keypad lockout for unauthorized users  
Manual temperature hold  
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:  
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•
•
•
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  
F
OF  
thermostat to expose the wiring connections.  
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. 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.  
4. 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.  
WIRING BASE PLATE NOTICE:  
This thermostat model is part of a family of similar models that have the  
same general visual appearance. Even though this base plate may look the  
same as base plates from other models, the wiring connections may have  
different terminal letters for different purposes. Please do not interchange  
the back plates and/or thermostat front halves of other similar looking  
models. Doing so may cause undesired heating and/or cooling operation  
to occur.  
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CAUTIONS AND WARNINGS:  
•
The 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 Lux thermostats requiring batteries. BE SURE TO CHANGE  
THE BATTERIES AT LEAST ONCE A YEAR. 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 which 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.  
Additional information is available at our website luxproducts.com. You  
should consult a qualified HVAC technician or an electrician if you do  
not fully understand the installation instructions.  
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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 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....................................8  
1-STAGE OR 2-STAGE  
2, 3, 4, 5 WIRES  
HEATING....................................9  
3-WIRE ZONE VALVE  
3, 4 WIRES  
COOLING..................................10  
1-STAGE  
3, 4 WIRES  
HEATING AND COOLING ................11  
1-STAGE HEAT  
4, 5 WIRES  
HEATING AND COOLING ................12  
2-STAGE HEAT  
5, 6 WIRES  
HEATING AND COOLING ................13  
TWO-TRANSFORMERS  
5, 6 WIRES  
HEATING AND COOLING ................14  
SINGLE-STAGE ONLY  
4, 5 WIRES  
HEAT PUMP:  
HEATING AND COOLING ................15  
WITH AUX / EMERGENCY HEAT  
5, 6 WIRES  
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2, 3, 4, 5 WIRES  
#1  
1-STAGE OR 2-STAGE, HEATING ONLY  
(INCLUDING MILLIVOLT) (2-WIRE HEAT USE “RH” & “W1”)  
Factory RH-RC Jumper Wire Installed  
O
B
G
Y
RC  
RH  
W1  
A
W2  
C
FAN WIRE  
MAY NOT BE  
PRESENT IN  
ALL SYSTEMS  
G
F
R
W
W2  
C
X
RH  
V
W1  
4
B*  
O
P
T
I
O
N
A
L
SYSTEM COMMON  
STAGE  
1
STAGE  
SYSTEM 24V  
TRANSFORMER  
FAN  
2
HEATER  
NOTE: THE BLACK TERMINAL LETTERS ARE TYPICAL, GRAY TERMINAL LETTERS ARE BRAND SPECIFIC  
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3, 4 WIRES  
#2  
HOT WATER HEATING ONLY  
(WITH A 3-WIRE ZONE VALVE)  
Factory RH-RC Jumper Wire Installed  
O
B
G
Y
RC  
RH  
W1  
A
W2  
C
R
W
A
C
X
RH  
V
W1  
4
B*  
O
P
T
I
O
N
A
L
SYSTEM COMMON  
OPEN  
CLOSE  
SYSTEM 24V  
TRANSFORMER  
3-WIRE ZONE VALVE  
OPEN = Heat On  
CLOSE = Heat Off  
NOTE: THE BLACK TERMINAL LETTERS ARE TYPICAL, GRAY TERMINAL LETTERS ARE BRAND SPECIFIC  
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3, 4 WIRES  
#3  
1-STAGE, COOLING ONLY  
Factory RH-RC Jumper Wire Installed  
O
B
G
Y
RC  
RH  
W1  
A
W2  
C
G
F
Y
Y1  
6
R
C
X
RC  
V
B*  
O
P
T
I
O
N
A
L
SYSTEM COMMON  
SYSTEM 24V  
TRANSFORMER  
AIR  
CONDITIONER  
FAN  
NOTE: THE BLACK TERMINAL LETTERS ARE TYPICAL, GRAY TERMINAL LETTERS ARE BRAND SPECIFIC  
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4, 5 WIRES  
#4  
CONVENTIONAL (NON HEAT PUMP)  
1-STAGE HEATING AND 1-STAGE COOLING  
Factory RH-RC Jumper Wire Installed  
O
B
G
Y
RC  
RH  
W1  
A
W2  
C
G
F
Y
Y1  
6
R
W
C
X
RH  
RC  
V
W1  
4
B*  
O
P
T
I
O
N
A
L
SYSTEM COMMON  
AIR  
CONDITIONER  
SYSTEM 24V  
TRANSFORMER  
FAN  
HEATER  
NOTE: THE BLACK TERMINAL LETTERS ARE TYPICAL, GRAY TERMINAL LETTERS ARE BRAND SPECIFIC  
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5, 6 WIRES  
#5  
CONVENTIONAL (NON HEAT PUMP)  
2-STAGE HEATING AND 1-STAGE COOLING  
Factory RH-RC Jumper Wire Installed  
O
B
G
Y
RC  
RH  
W1  
A
W2  
C
G
F
Y
Y1  
6
R
W
W2  
C
X
RH  
RC  
V
W1  
4
B*  
O
P
T
I
O
N
A
L
SYSTEM COMMON  
STAGE  
1
STAGE  
2
AIR  
CONDITIONER  
SYSTEM 24V  
TRANSFORMER  
FAN  
HEATER  
NOTE: THE BLACK TERMINAL LETTERS ARE TYPICAL, GRAY TERMINAL LETTERS ARE BRAND SPECIFIC  
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5, 6 WIRES  
#6  
1-STAGE HEATING AND 1-STAGE COOLING  
WITH TWO SEPARATE 24V TRANSFORMERS  
Factory RH-RC Jumper Wire REMOVED  
O
B
G
Y
RC  
RH  
W1  
A
W2  
C
G
F
Y
RC  
RH  
W
C
X
Y1  
6
R
V
R
V
W1  
4
B*  
O
P
T
I
O
N
A
L
SYSTEM COMMON  
AIR  
CONDITIONER  
COOL 24V  
TRANSFORMER  
HEAT 24V  
TRANSFORMER  
FAN  
HEATER  
NOTE: THE BLACK TERMINAL LETTERS ARE TYPICAL, GRAY TERMINAL LETTERS ARE BRAND SPECIFIC  
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SINGLE-STAGE HEAT PUMP SYSTEM  
WITH NO AUX OR EMERGENCY HEAT  
4, 5 WIRES  
#7  
** Use “O” or “B”  
Terminals, Never Both  
CUSTOMER INSTALLED Y-W1 Jumper Wire  
Factory RH-RC Jumper Wire Installed  
O
B
G
Y
RC  
RH  
W1  
A
W2  
C
O
G
F
Y
Y1  
6
R
C
X
RC  
V
B*  
O
P
T
I
O
N
A
L
SYSTEM COMMON  
REVERSING  
VALVE  
SYSTEM 24V  
TRANSFORMER  
FAN  
HEAT PUMP  
NOTE: THE BLACK TERMINAL LETTERS ARE TYPICAL, GRAY TERMINAL LETTERS ARE BRAND SPECIFIC  
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5, 6 WIRES  
2-HEAT / 1-COOL, HEAT PUMP SYSTEM  
WITH AUX AND EMERGENCY HEAT  
#8  
** Use “O” or “B”  
Terminals, Never Both  
CUSTOMER INSTALLED Y-W1 Jumper Wire  
Factory RH-RC Jumper Wire Installed  
O
B
G
Y
RC  
RH  
W1  
A
W2  
C
O
G
F
Y
R
W2  
C
X
Y1  
6
RC  
V
W3  
W
B*  
O
P
T
I
O
N
A
L
SYSTEM COMMON  
REVERSING  
VALVE  
SYSTEM 24V  
TRANSFORMER  
AUX / EMERG.  
HEAT  
FAN  
HEAT PUMP  
NOTE: THE BLACK TERMINAL LETTERS ARE TYPICAL, GRAY TERMINAL LETTERS ARE BRAND SPECIFIC  
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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  
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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 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.  
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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).  
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.  
BATTERY  
[DOWN = GAS, default] This setting lets  
the heating system control the blower fan  
automatically by itself. Systems that  
would typically use the “GAS” setting  
ELEC  
would be: natural gas, propane, or oil  
furnaces. This setting has no effect upon  
Cool mode operation. [UP = ELEC/HP]  
GAS  
This setting runs the system’s blower fan  
when 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.  
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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 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.  
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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.  
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.  
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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 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.  
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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 weekend program, with the MORN period start  
time flashing. You will be setting the program periods for both Saturday  
and Sunday (grouped together). Perform the same steps that you used  
for setting the weekday 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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71  
70  
69  
68  
67  
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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 “CAL” will 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.  
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. 
this 2-digit code is “00”, and the temperature stops can be uh  
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KEYPAD LOCKOUT: You can lock the front panel buttons to prevent  
unauthorized tampering of your thermostat settings.  
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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 Air Filter Monitor counts the duration of filter usage that has  
occurred, since the last time the Filter Monitor has been reset. 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 completely expired, 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 word “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 top of the screen  
tell you the quantity of filter days remaining. Press both the UP and  
DOWN buttons together, 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 of  
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  
HW RST  
switches, and will perform an internal system  
check of the thermostat 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 of  
the circuit board, just below the battery holder.  
A Software Reset is used to erase all heating  
and cooling temperature programs, and any  
SW RST  
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,  
then return to normal. The thermostat will still retain the current day and  
time even after a Software Reset has been performed.  
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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.  
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.  
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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 night at  
http://www.luxproproducts.com. Our website offers you troubleshooting  
guides, answers to the most common technical questions, and also  
permits you to email your questions to our technical support staff at your  
convenience.  
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
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DAY  
5 36  
P
FAN  
HEAT  
˚F  
˚
72  
ROOM  
S
ET 74  
HOLD  
Mt. Laurel, New Jersey 08054, USA  
http://www.luxproproducts.com  
856-234-8803  
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