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OPERATING INSTRUCTIONS  
Complete, Easy To Read  
INSTALLATION AND OPERATING INSTRUCTIONS  
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In the winter, set the system switch to HEAT to control your system while  
heating.  
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In the summer, set the switch to COOL to control your system while cooling.  
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Press the TEMPERATURE UP or DOWN key in order to show the  
current SET TEMPERATURE.  
Press TEMPERATURE UP or DOWN keys again until your desired  
temperature is displayed. The display will show the current room temperature  
again after two seconds.  
PSDH121 SERIES  
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DIGITAL ELECTRONIC HEAT PUMP THERMOSTAT  
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Press the light bulb button to illuminate the display. Adjusting the temperature  
Easy as  
HEAT  
OFF  
COOL  
will keep the display lit until no button has been pressed for over ten seconds.  
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1–2–3  
In spring and fall or when windows are open, you can set the system switch  
Installs Easily  
Choose Heat or Cool  
Set Temperature  
to OFF.  
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LUX PRODUCTS CORPORATION • Mt. Laurel, New Jersey 08054, USA  
43368  
Setting the FAN switch to AUTO automatically runs your system’s fan during  
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.  
heating and cooling.  
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Setting the FAN switch to ON runs your system’s fan continuously even  
without heating or cooling.  
I M P O R T A N T !  
Please read all instructions carefully before  
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Setting the Mode switch to EMER (emergency heat) runs your Emergency  
heating system rather than the heat pump.  
beginning installation and save for future reference.  
Before removing any wiring from your existing thermostat, its wires  
must be labeled with their terminal designations.  
N O T E  
The FAN switch works only if your system provides a wire for a thermostat’s “G” terminal.  
Ignore the color of the wires since they may not comply with any standard.  
Thank you for your confidence in our product. To obtain the best results from  
your investment, please read this manual 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. These instructions may  
contain information beyond that required for your particular installation. Please  
save for future reference.  
INSTALLATION  
Please read all instructions carefully before beginning installation.  
C A U T I O N  
*** 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. ***  
OFF  
COMPATIBILITY  
TEMP UP  
MODE  
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Do not short (jumper) across electric terminals at control on furnace or air  
LUX PSDH121 was designed  
for use with single stage heat  
pump systems with auxiliary  
and/or emergency heat. These  
systems are typical known as  
2-stage heat one stage cool heat  
pump systems.  
conditioner to test the system. This will damage the thermostat and void  
your warranty.  
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All wiring must conform to local codes and ordinances.  
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This thermostat is designed for use with 24 volt systems. The thermostat  
should be limited to a maximum of 1.5 amps; higher current may cause  
damage to the thermostat. If you are in doubt, call your HVAC contractor.  
FAN  
MODE  
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Your thermostat is a precision instrument. Please handle it with care.  
BACKLIGHT  
RESET  
TEMP DOWN  
TOOLS REQUIRED  
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#1 Phillips screwdriver (small)  
FEATURES  
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Drill with 3/16-in. (4.8mm) bit  
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Slim design may be vertically or horizontally  
mounted  
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Wire stripper/cutter  
THERMOSTAT LOCATION  
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Large easy to read backlit display  
Fan switch for system or continuous fan  
operation  
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.  
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Emergency Heat Switch  
Simple temperature Up or Down keys will  
display and adjust the Set Temperature.  
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Remember that your PSDH121 may be mounted vertically or horizontally  
when determining the optimal location.  
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Locate the thermostat on an inside wall, about 5 ft. (1.5m) above the floor,  
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and in a room that is used often.  
Temperature displays in F° or C°  
Temperature differential SWING settings of  
0.25 and 0.5  
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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.  
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Selectable 2 or 5-Minute Minimum Run/Off time provides short cycle and  
compressor protection  
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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.  
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Do not locate in a damp area. This can lead to corrosion that will shorten  
thermostat life.  
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Do not locate where air circulation is poor, such as: in a corner or an alcove;  
or behind an open door.  
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Do not install the unit until all construction work and painting has been  
completed.  
© COPYRIGHT 2004 LUX PRODUCTS CORPORATION. ALL RIGHTS RESERVED  
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C A U T I O N  
Do not allow wires to touch each other or parts on thermostat. Terminated wires must  
be trapped between black spacer and brass terminal. Securely tighten all eight electrical  
terminal screws.  
C A U T I O N  
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 they may not comply with any standard.  
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REMOVING THE OLD THERMOSTAT  
1. Switch electricity to the furnace and air conditioner OFF; then  
proceed with the following steps.  
2. Remove cover from old thermostat. Most are snap-on types and  
simply pull off. Some have locking screws on the side. These must  
J4 J3 J2 J1  
JUMPER POSITIONS  
(FOR REFERENCE ONLY  
NOT SHOWN TO SCALE)  
be loosened.  
3. Note the letters printed near the terminals. Attach labels (enclosed) to each wire  
for identification. Label and remove wires one at a time. Make sure the wires do  
not fall back inside the wall.  
4. Loosen all screws on the old thermostat and remove it from the wall.  
MOUNTING THE PSDH121 ON THE WALL  
1. Decide whether the thermostat will be mounted vertically or horizontally.  
INSTALLATION OPTIONS  
There are four options which are set by a group of numbered jumpers on the  
rear of the units circuit board. They are:  
J1: The minimum run time jumper J1 sets the minimum length of time that the  
thermostat must remain with Heat or Cool either on or off before it will  
automatically switch to the alternate On or Off state. This feature prevents short  
cycling, and provides compressor protection for cooling units. Choices are 2 or 5  
minutes.  
C A U T I O N  
Be careful not to drop the unit or disturb electronic parts.  
2. Strip insulation 3/8 in. (9.5mm) from wire ends and  
clean off any corrosion.  
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3. Fill wall opening with non-combustible insulation to  
prevent drafts from affecting the thermostat.  
J2: The temperature format: jumper selects whether your thermostat displays  
temperatures in Celsius or Fahrenheit.  
4. Cup the thermostat with one hand behind the  
thermostats display. Separate the unit from its base  
plate using the tabs protruding from its body with  
the other hand.  
J3: This Jumper determines whether the display will be horizontally or vertically  
oriented.  
J4: This Jumper controls the “swing” or temperature variation in the home. Using  
the smaller number results in more stable temperature, while the wider setting is  
provided as a more energy efficient alternative. Users of force hot water systems  
may find the 0.25 setting more comfortable.  
TAB  
N O T E  
The table at left is printed on the  
BASE  
If you are mounting the base to a  
CLOSE  
5 min  
F
Horizontal  
Swing=0.5  
OPEN  
2 min  
C
Vertical  
Swing=0.25  
circuit board. To change a jumper  
position. The closed or shorted  
position is that which covers both a  
jumpers pins. To prevent its loss, a  
jumper may be placed over one pin  
only for the open positions. After  
settings have been changed, press  
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.  
J1  
J2  
J3  
J4  
Then mount the base as  
described below.  
TERMINALS  
the small-unmarked RESET button on the front of the thermostat for the changes  
to take effect.  
ATTACHING WIRES  
5. Route the wires through the large hole in the base plate by the  
terminal block. Hold the base against the wall, with the wires  
coming through. Position the base for best appearance (to hide  
any marks from an old thermostat). The terminal block should be  
either to the right of or below the routing hole. Attach the base to  
the wall with the two screws provided.  
INSTALL BATTERIES  
For detailed instruction, see BATTERIES/MAINTENANCE to install batteries at  
this time.  
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Turn the power back on to your heating and/or air conditioning system.  
Verify that the system and its fan are operating properly. When set to a high  
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temperature, the heating system should provide warm air after a short time.  
Likewise, a cooling system should provide cool air after a short time. Usually sound  
from the furnace and air conditioning units can be heard while they are running.  
The rush of moving air should be heard within a short time after either has been  
started.  
PLEASE REVIEW THE WIRING DIAGRAMS IN THE NEXT COLUMN  
FOR PROPER TERMINAL CONNECTION  
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The Installation is now complete.  
CALIBRATION  
Your thermostat is carefully calibrated at the factory, and will measure  
temperature to within 1°. However, you can adjust the reading of your  
thermostat:  
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Slide the MODE switch to OFF.  
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Press and hold the Up and Down buttons until the display shows a single digit  
between +5F°(+3C°) and -5F°(-3C°).  
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Then the Up or Down buttons may be used to adjust the reading.  
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The display will return to normal operation after 4 seconds without an  
adjustment.  
© COPYRIGHT 2004 LUX PRODUCTS CORPORATION. ALL RIGHTS RESERVED  
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NEW THERMOSTAT AND  
CORRESPONDING TERMINALS  
TAPE OFF  
(NOT USED)  
BATTERIES/MAINTENANCE  
HEAT PUMP SYSTEM  
WITH COMMON TERMINAL  
1. Remove fresh batteries from their carton.  
2. Remove body of thermostat as described during installation.  
3. Remove the used batteries if present.  
4. Install two new Energizer® or DURACELL® "AA" size alkaline batteries in the  
battery compartment. Observe the polarity marking shown in the compartment.  
WARNING: Use Energizer® or DURACELL® Alkaline Batteries Only.  
5. Place the body back on the wall.  
6. Using a small Phillips screwdriver press the RESET button which is between  
the Up/Down arrow button. Within 90 seconds the thermostat will begin to  
display the room temperature.  
BATTERY COMPARTMENT  
N O T E  
REPLACE BATTERIES WHEN LOBAT APPEARS IN THE DISPLAY  
OR AT LEAST ONCE A YEAR.  
WIRING DIAGRAMS  
These diagrams are provided for new installations or un-referenced wires.  
TYPICAL HEAT PUMP WITH AUX HEAT  
ALSO WIRED AS EMERGENCY HEAT  
TECHNICAL SERVICE  
USE "B" OR "O"  
BUT NOT BOTH  
If you have any problems installing or using this thermostat, please reread the  
instructions carefully. Technical Service is available through our Technical  
Assistance Dept. If you require assistance, please call our offices between 8:00  
a.m. and 4:30 p.m. Eastern Standard Time, Monday through Friday. The number  
E
Y
HEAT PUMP  
COMPRESSOR  
B
B
O
CHANGEOVER  
OR  
WARRANTY  
VALVE  
O
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. 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.  
AUX/EMER  
W2  
R
HEAT  
24VAC  
AC  
XFMR  
LINE  
G
FAN  
C
OPTIONAL  
COMMON  
NOTE: ADD JUMPER SHOWN BETWEEN "W2" AND "E"  
IF "E" IS NOT PRESENT  
© COPYRIGHT 2004 LUX PRODUCTS CORPORATION. ALL RIGHTS RESERVED  
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