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Your thermostat is a precision instrument. Please handle it with care.  
INSTALLATION AND OPERATING INSTRUCTIONS  
Turn off electricity to the appliance before installing or servicing thermostat or any  
part of the system. Do not turn electricity back on until work is completed.  
• Do not short (jumper) across electric terminals at control on furnace or air  
conditioner to test the system. This will damage the thermostat and void your  
warranty.  
TX250 SERIES  
• All wiring must conform to local codes and ordinances.  
SMART TEMP ELECTRONIC THERMOSTAT  
• This thermostat is designed for use with 24 volt and millivolt systems. The  
thermostat should be limited to a maximum of 1.0 amps; higher amperage may  
cause damage to the thermostat. If you are in doubt, call your utility company.  
Easy as  
EAT  
L  
1–2–3  
Installs Easily  
Set Day & Time  
Choose Heat or Cool  
INSTALLATION  
before beginning installation.  
TOOLS REQUIRED  
#1 Phillips screwdriver (small)  
Drill with 3/16-in. (4.8mm) bit  
C A U T I O N  
Complete, Easy To Read Programming And Installation Instructions Inside  
To avoid electrical shock and  
Please read all instructions carefully  
LUX PRODUCTS CORPORATION • Mt. Laurel, New Jersey 08054, USA  
43374  
to prevent damage to the  
F
OF  
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.  
furnace, air conditioner, and  
thermostat, disconnect the power  
supply before beginning work. This  
can be done at the fuse box, at the  
circuit breaker, or at the appliance.  
I M P O R T A N T !  
THERMOSTAT LOCATION  
Thank you for your confidence in our product. To obtain the best results  
On replacement installations, mount the new thermostat in place of the old one  
unless the conditions listed below suggest otherwise. On new installations, follow  
the guidelines listed below.  
READ  
from your investment, please read these instructions and acquaint yourself with  
your purchase before installing your new thermostat. Then follow the  
installation procedures, one step at a time. This will save you time and  
minimize the chance of damaging the thermostat and the systems it controls.  
INSTALLATION  
INSTRUCTIONS  
FIRST  
1. Locate the thermostat on an inside wall, about 5 ft. (1.5m) above the floor, and in  
a room that is used often.  
These instructions may contain information beyond that required for your particular installation.  
Please save for future reference.  
2. Do not install it where there are unusual heating conditions, such as: in direct  
sunlight; near a lamp, radio, television, radiator, register, or fireplace; near hot  
water pipes in a wall; near a stove on the other side of a wall.  
3. Do not locate in unusual cooling conditions, such as: on a wall separating an  
unheated room; or in a draft from a stairwell, door, or window.  
4. Do not locate in a damp area. This can lead to corrosion that will shorten  
thermostat life.  
5. Do not locate where air circulation is poor, such as: in a corner or an alcove; or  
behind an open door.  
6. Do not install the unit until all construction work and painting has been completed.  
FEATURES  
The TX250 can be  
used with most 24  
volt gas, oil or  
Liquid Crystal  
Display  
Thermostat  
Body  
Fan Switch  
electric heating  
and air  
conditioning  
systems, single-  
stage heat pumps  
or gas millivolt  
heating systems.  
It cannot be used  
with 120 volt heating  
systems or multistage  
heat pumps. Ask your  
dealer for other LUX  
thermostats to  
7. This thermostat does not require leveling.  
C A U T I O N  
REMOVING THE OLD THERMOSTAT  
Switch electricity to the furnace and air conditioner  
OFF; then proceed with the following steps.  
Read instructions carefully  
before removing any  
wiring from existing  
thermostat. Wires must be  
labeled before they are  
removed. When removing  
wires from their terminals,  
ignore the color of the  
wires since these may not  
Reset  
1. Remove cover from old thermostat.  
Most are snap-on types and simply  
pull off. Some have locking screws  
on the side. These must be loosened.  
Button  
control those  
Mode  
2. Note the letters printed near the terminals. Attach  
systems.  
Switch  
Separator  
Tabs  
labels (enclosed) to each wire for identification.  
The TX250 is  
Speed  
Slide  
comply with the standard.  
Remove and label wires one at a time. Make sure the  
programmable.  
There are four  
wires do not fall back inside the wall.  
3. Loosen all screws on the old thermostat and remove it from the wall.  
programming periods  
per day. Each period can be programmed separately.  
MOUNTING THE TX250 ON THE WALL  
2. Fill wall opening with  
non-combustible  
insulation to prevent  
drafts from affecting  
the thermostat.  
Easy to use Speed Slide.  
R
You can use the built-in time/temperature programs, or alter them to suit your  
schedule. The TX250 provides separate programming for weekdays and weekends  
— for both heating and cooling. You can override the programmed temperatures for  
as little as one programming period or for an entire vacation.  
1. Strip insulation 3/8 in.  
(9.5mm) from wire ends  
and clean off any corrosion.  
In cool weather, when the system switch is set to HEAT, the TX250 may maintain  
cooler “set back” room temperatures to save energy. It will then change to warmer  
“comfort” settings — automatically, at specified times during the day.  
In warm weather, when the system switch is set to COOL, the TX250 may maintain  
warmer “set back” room temperatures to save energy. It will then change to cooler  
“comfort” settings — automatically, at specified times during the day.  
3. Cup and hold thermostat body and left tab in place with left hand. Separarte tabs  
with right hand.  
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Be careful not to drop the body or disturb electronic parts.  
A liquid crystal display shows time, day of the week, and room and set  
temperatures.  
Temperature swing adjustment lets you fine-tune your system for maximum  
comfort and economy.  
A 2 or 5-minute minimum off time in COOL prevents your air conditioning system  
from being damaged.  
Two Energizer or DURACELL “AA” alkaline batteries (not included) are used to  
retain your time and temperature programs.  
®
®
© COPYRIGHT 2004 LUX PRODUCTS CORPORATION. ALL RIGHTS RESERVED  
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Base  
Terminals  
N O T E  
TYPICAL HOOKUP FOR 2-WIRE  
24V HEATING SYSTEM AND  
MILLIVOLT SYSTEM  
TYPICAL HOOKUP FOR 3-WIRE  
HEAT SYSTEM IF THIRD  
WIRE IS FAN WIRE  
TYPICAL COOLING AND  
HEATING SYSTEM  
(4-WIRE)  
If you are mounting the base to  
a soft material like plasterboard  
or if you are using the old  
mounting holes, the screws  
may not hold. Drill a 3/16-in.  
(4.8mm) hole at each screw  
location, and insert the plastic  
anchors provided. Then mount  
the base as described below.  
FAN  
FAN  
COOL  
COMP  
GAS  
GAS  
GAS  
VALVE  
VALVE  
VALVE  
24 VAC  
TRANSFORMER  
OR  
24 VAC  
HEAT  
Latch Button  
24 VAC  
TRANSFORMER  
TRANSFORMER  
ATTACHING WIRES  
THERMOPILE  
4. Hold the base against the wall, with the wires coming through  
wherever it is convenient for wiring. Route the wires to the  
terminal block. Position the base for best appearance (to hide  
any marks from an old thermostat). Attach the base to the wall  
with the two screws provided.  
110  
110  
110  
TYPICAL COOLING AND  
HEATING SYSTEM  
(5-WIRE)  
TYPICAL SINGLE-STAGE  
HEAT PUMP WIRING  
FAN  
FAN  
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COOL  
COMP  
Do not allow wires to touch each other or parts on thermostat. Wires must be trapped between  
black spacer and brass terminal. Also, be sure to securely tighten all 7 electrical terminal screws.  
COMP  
GAS  
VALVE  
WIRING DIAGRAMS  
24 VAC  
HEAT  
24 VAC  
COOL  
ALTERNATE  
TRANSFORMER TRANSFORMER  
HEATING SYSTEMS  
COOLING SYSTEMS  
24 VAC  
HEAT  
CHANGE  
OVER  
B
TAPE OFF  
*
110  
110  
TRANSFORMER  
C
ALTERNATE  
TAPE OFF**  
TAPE OFF  
REMOVE JUMPER BETWEEN "RC" AND "RH"  
110  
TC  
TC  
TAPE OFF  
Y
ADD JUMPER BETWEEN "Y" AND "W"  
G F  
G F  
FAN RELAY  
FAN RELAY  
N O T E  
C
*
COOLING COMPRESSOR  
COOLING COMPRESSOR  
If you have an electric system and the blower does not operate after installation, find the  
electric/gas heat jumper on the back of the body. Move the jumper to the ELEC position.  
4 H W  
HEATING CONTROL  
COOL TRANSFER  
HEATING CONTROL  
COOL TRANSFER  
V R RC  
5 V R RC RH  
INSTALLING BATTERIES/ MAINTENANCE  
The TX250 requires batteries to operate your furnace and retain its  
programming in memory. Replace the batteries when the REPLACE indicator  
appears in the display or at least once a year.  
*
HEATING TRANSFER  
HEATING TRANSFER  
DAMPER OR CHANGEOVER  
VALVE (Powered in Cool)  
DAMPER OR CHANGEOVER  
VALVE (Powered in Heat)  
DAMPER OR CHANGEOVER  
VALVE (Powered in Cool)  
DAMPER OR CHANGEOVER  
VALVE (Powered in Heat)  
REPLACE BATTERIES WHEN  
INDICATOR APPEARS  
OSE  
If replacing a Honeywell TM-11, tape off wire "R";  
connect wire "B" to terminal "RH".  
If both "Y" and "C" wire are present, tape off "C" wire.  
IN  
*
*
LO BAT  
OR AT LEAST  
If replacing a Honeywell thermostat with a clock wire "C",  
tape off wire "C".  
**  
ONCE A YEAR.  
HR  
1. Remove fresh batteries from their carton.  
2. Cup and hold thermostat body and left tab  
HEATING / COOLING SYSTEMS  
HEATING / COOLING SYSTEMS  
Battery  
in place with left hand. Separarte tabs  
Compartment  
4- or 5-WIRE WITH ONE TRANSFORMER  
5- or 6-WIRE WITH TWO TRANSFORMERS  
with right hand.  
3. Remove the used batteries.  
N O T E  
TC  
TC  
TAPE OFF  
C
TAPE OFF  
Y
4. Install two new Energizer® or DURACELL® "AA"  
When replacing batteries, you  
size alkaline batteries in the battery compartment.  
F G  
F G  
have approximately 1 minute  
before programs are lost.  
Observe the polarity marking shown in the  
compartment. Place body back on wall.  
FAN RELAY  
FAN RELAY  
Y
C
*
*
COOLING COMPRESSOR  
COOLING COMPRESSOR  
W
W
WARNING: Use Energizer® or DURACELL®  
HEATING CONTROL  
COOL TRANSFER  
HEATING CONTROL  
COOL TRANSFER  
5. Align the top of the body onto  
the base and press together.  
Alkaline Batteries Only.  
V R RC  
4 A RH  
V R RC  
Installation is now complete. Be sure to turn the power back on to your heating  
and /or air conditioning system. If this is the first time you are installing batteries, the  
thermostat will display “SUN 12:00 AM”. Within 90 seconds the thermostat will begin  
to display the room temperature alternately with the time. To correct the display, see  
“Setting the TIME and DAY,” after you set the programs.  
HEATING TRANSFER  
HEATING TRANSFER  
O
B
O
B
OPTIONAL  
OPTIONAL  
OPTIONAL  
OPTIONAL  
DAMPER OR CHANGEOVER  
VALVE (Powered in Cool)  
DAMPER OR CHANGEOVER  
VALVE (Powered in Heat)  
DAMPER OR CHANGEOVER  
VALVE (Powered in Cool)  
DAMPER OR CHANGEOVER  
VALVE (Powered in Heat)  
If both "Y" and "C" wire are present, tape off "C" wire.  
If both "Y" and "C" wire are present, tape off "C" wire.  
*
*
P R O G R A M M I N G  
C H A R T  
DAY  
PERIOD  
HEAT  
COOL  
These diagrams below are provided for new installations or unreferenced wires.  
TIME  
TEMP.  
TIME  
TEMP.  
MON.  
THRU  
FRI.  
MORN  
DAY  
EVE  
NIGHT  
MORN  
DAY  
SAT.  
and  
EVE  
SUN.  
NIGHT  
© COPYRIGHT 2004 LUX PRODUCTS CORPORATION. ALL RIGHTS RESERVED  
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TEMPERATURE HOLD  
• Press HOLD. Adjust temperature as  
desired with UP/DOWN.  
Temperature setting will not change even  
after next program period begins.  
To clear, press HOLD again.  
MO  
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This thermostat is “armchair programmable”  
You can make any program or setting  
changes with the thermostat body off or on  
the wall thermostat base.  
OPERATION  
66  
DAY  
HOLD  
The TX250 alternately displays the  
current time and the room  
PM  
HOLD  
temperature. It also displays the day of  
the week and the currently active  
program period that is controlling the temperature: MORN, DAY, EVE, or NITE.  
The set point temperature will appear in the right side of the display. In the winter, set the  
system switch to HEAT to control your heating system. In the summer, set the switch to  
COOL to control your air conditioner. In spring and fall or when windows are open, you can  
set the system switch OFF.  
ADVANCED FEATURES  
TEMPERATURE SWING  
A thermostat works by turning your heating or cooling system on and off whenever the  
room temperature varies a certain number of degrees from the set-point temperature. This  
variation is the “swing.”  
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Setting the FAN switch to AUTO  
automatically runs your system’s fan  
during heating and cooling. Setting  
the FAN switch to ON runs your  
The FAN switch works only if your system  
provides a wire for the TX250’s “G” terminal.  
Your system should cycle on about 3 to 6 times per hour. A smaller swing number  
increases the number of cycles, so room temperature is more constant. Setting “1” is  
approximately 1/4°F. Each increase of 1 value increases the swing by approximately 1/4°F.  
A larger swing number decreases the number of cycles, and may save energy in some  
cases.  
system’s fan continuously even without heating or cooling.  
®
THE BUILT-IN ENERGY STAR PROGRAMS  
Push in the RESET key. This  
PERIOD  
HEAT  
COOL  
sets the default heating and  
cooling programs. To review the  
default programs, move the Speed  
Slide to SET WEEKDAY or  
SET WEEKEND.  
HOLD  
NEXT  
Press together  
SWING SETTINGS  
WEEKDAYS  
preprograms  
MORN  
DAY  
EVE  
6:00 AM 70° 6:00 AM 78°  
8:00 AM 62° 8:00 AM 85°  
6:00 PM 70° 6:00 PM 78°  
SET TEMP SWING  
Speed Slide must  
be in the run  
position  
To change  
swing  
DOWN  
UP  
NEXT  
Press to set.  
You can use the default  
NIGHT 10:00 PM 62° 10:00 PM 82°  
programs as shown, or change  
them as you wish. Each day is  
divided into four periods. Each  
period has its own starting time  
and temperature.  
MORN  
DAY  
6:00 AM 70° 6:00 AM 78°  
8:00 AM 62° 8:00 AM 85°  
6:00 PM 70° 6:00 PM 78°  
WEEKEND  
W
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G
preprograms  
EVE  
Making these changes will require you to reset the thermostat. Copy any of your customized  
programs onto the blank chart. This will be your reference to re-enter the programs afterwards.  
NIGHT 10:00 PM 62° 10:00 PM 82°  
PROGRAMMING THE TX250  
CHANGING FROM °F TO °C AND A 12HR CLOCK TO A 24HR CLOCK  
You can change any preset times and/or temperatures to suit your schedules for the  
weekday and weekend programs. Each period (Morning, Day,  
Evening, and Night) is programmed for HEAT and for COOL.  
MO TU WE TH FR  
MORN  
WARNING: Making these changes will  
require you to reset the thermostat. Copy  
any of your customized programs onto  
the chart below. This will be your  
reference to reenter the programs  
afterwards.  
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AM  
HEAT  
OFF  
OPEN CLOSE  
Select HEAT to program the  
TX250 for controlling your heater.  
OR  
Select COOL to program the  
TX250 for controlling your air conditioner.  
COOL  
JP3 2MIN 5MIN  
Located to the left of the circuit board  
are three black jumpers C/F and 24/12H.  
To change to Celsius - remove jumper  
JP2  
C
F
Slide the Speed Slide to SET WEEKDAY PROGRAM. To program the weekends SET  
WEEKEND. With Slide on SET WEEKDAY PROGRAM, you will see the display above.  
JP1 24HR 12HR  
- JP2.  
JP3  
To change to a 24HR clock - remove  
JP2  
JP1  
jumper- JP1.  
To change the start  
time for MORN.  
To change the start  
time for EVE.  
To program temperature.  
DOWN  
DOWN  
UP  
UP  
Press the reset key on the front of the  
thermostat for changes to take effect.  
• Reprogram as necessary.  
NEXT  
UP  
NEXT  
UP  
To program temperature.  
To change the temp.  
setting for MORN.  
To move to DAY.  
To change start time  
for DAY.  
To change the temp.  
DOWN  
DOWN  
setting for EVE.  
To move to NIGHT.  
To change the start  
time for NIGHT.  
To program temperature.  
To change the temp.  
setting for NIGHT.  
5 MIN/2 MIN MINIMUM ON/OFF TIME  
NEXT  
UP  
NEXT  
UP  
Your thermostat has an internal timer built in to protect your compressor. The timer forces  
a minimum on/off time of 5 minutes. You may change this minimum on/off time to 2 minutes.  
To accomplish this, remove the jumper labeled JP3. You must press the small reset  
button on the face of the thermostat for the changes to take effect.  
DOWN  
DOWN  
NEXT  
UP  
NEXT  
UP  
To program temperature.  
DOWN  
DOWN  
To change the temp.  
setting for DAY.  
To move to EVE.  
TECHNICAL SERVICE  
If you have any problems installing or using this thermostat, please reread the instructions carefully.  
Technical Service is available through our Technical Service Number. If you require assistance, please  
call our offices between 8:00 a.m. and 4:30 p.m. Eastern Standard Time, Monday through Friday.  
NEXT  
Move Speed Slide to RUN position to  
start the programs.  
SETTING THE TIME AND DAY  
WARRANTY  
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Limited Warranty: If this unit fails because of defects in materials or workmanship within one year of  
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 one year from 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 participating retailer from which purchase was made, along with proof of  
purchase. Please refer to Technical Service Section before returning thermostat.  
The TX250 is protected against normal static electric discharges.  
However, in extremely dry weather you should touch another metal  
object before the TX250 to avoid potential loss of programs.  
PM  
Move the Speed Slide to SET DAY/TIME position. You should see the display pictured  
above with a day of the week flashing. When you are finished setting the day and time,  
rotate the dial to RUN to return to normal operation or to another position to continue  
programming.  
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. only.  
UP  
To change  
current day.  
To set current time. The (e.g.  
“12:00”) will be flashing.  
To change the  
current time.  
UP  
NEXT  
DOWN  
These features let you change the current  
Set Temperature without changing the programs  
stored in your thermostat’s memory.  
TEMPERATURE OVERRIDE AND  
TEMPERATURE HOLD  
TEMPORARY  
Press UP/DOWN to change the current temperature  
setting. The OVERRIDE indicator appears on display.  
The OVERRIDE feature will be automatically canceled  
at the start of the next program period.  
TEMPERATURE OVERRIDE  
MO  
H
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UP  
To cancel OVERRIDE prior to next program period press  
UP/DOWN until original set temperature  
DAY  
PM  
DOWN  
OVERRIDE  
appears. OVERRIDE indicator will disappear from display.  
© COPYRIGHT 2004 LUX PRODUCTS CORPORATION. ALL RIGHTS RESERVED  
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