KEYPAD LOCKOUT: You can lock the front panel buttons to prevent unauthorized tampering of your
thermostat settings. The following examples use the default lock code of “0000”. If you have altered
the lock code to use your own code, use that in place of “0000” in the following instructions.
THERMOSTAT FRONT PANEL:
INSTALLATION AND OPERATING INSTRUCTIONS
EMER / HEAT / OFF / COOL, SYSTEM MODE SWITCH: Set this switch to HEAT to control your heating
system, and COOL to control your cooling system. To disable the heat pump unit and operate only on
your Auxiliary/Emergency heating source, use the EMER position. The OFF position will disable both the
heating and cooling units.
NOTE: These keypad lock instructions need to be performed in a timely manner, as the thermostat will
timeout and automatically exit the keypad lock screen and return to the normal run screen after 12
seconds without a button press.
PH521 5/2-Day Programmable
Heat Pump Thermostat
AUTO / ON, FAN SWITCH: When this switch is in AUTO, the blower fan will automatically cycle on and
off by itself when 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 in OFF mode.
TO LOCK THE KEYPAD: Place the Set Slide Switch in the RUN position, and press NEXT for at least 6
seconds. Enter the correct code by using UP or DOWN to change the flashing digit, and use NEXT to
cycle through which digit is flashing. Press NEXT for at least 4 seconds. A padlock should appear on
the screen to confirm that the thermostat is now locked.
Lux Products Corporation
Mt. Laurel, New Jersey 08054
MULTI-FUNCTION, SET SLIDE SWITCH: Unless other settings are being adjusted, this switch should
always remain in the RUN position for the thermostat to control temperature. When this switch is in
the DAY/TIME position, the day and clock can be changed. When this switch is in the WEEKDAY or
WEEKEND positions, the heating and cooling temperature program periods can be adjusted. NOTE: this
switch is only used in “Program” mode. When the thermostat is used in “Manual” control mode, all
four of the switch positions will act like the RUN position.
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.
TO UNLOCK THE KEYPAD: A press of any button will show “0000” on the screen. Enter the correct code
by using UP or DOWN to change the flashing digit, and use NEXT to cycle through which digit is
flashing. Press NEXT for at least 4 seconds. The padlock should disappear, and the thermostat should
now be unlocked. If you try to unlock the thermostat by entering a code that is not correct, the display
will flash “8888” on the screen.TO CHANGE THE LOCK CODE: First ensure that the thermostat is
unlocked, and the Set Slide Switch is in the RUN position. Press NEXT for at least 6 seconds. When
“0000” is displayed, release NEXT then press HOLD for at least 4 seconds until the word “SET” appears.
Enter your new desired code by using UP or DOWN to change the flashing digit, and use NEXT to cycle
through which digit is flashing. Press NEXT for at least 4 seconds until the word “SET” is no longer
shown. Your new code has been accepted. You may either: press NEXT for at least 4 seconds to lock
the thermostat using your new code, or let the screen timeout on its own after 12 seconds and return to
the normal run screen.
Thank you for your confidence in our product. To obtain the best results from your investment, please
read these instructions and acquaint yourself with your purchase. Follow the installation procedures
carefully, and save these instructions for future reference. This will save you time and minimize the
chance of damaging either the thermostat or the systems that it controls. NOTE: These instructions may
contain information beyond that required for your particular installation.
RESET BUTTON: There is a small recessed push button located to the left of the DOWN button, which
can be pressed with a pen/pencil, paper clip, or similar object. A single press of this button causes the
LCD display screen to become fully populated, the heating/cooling load relay to cycle off, and performs
an internal system check of the thermostat components. If your thermostat is acting in an erratic
manner, pressing the Reset button may remedy this behavior. If your thermostat continues to act
erratically, a Full Software Reset may be needed. This and other additional features that can be
accessed using the same Reset button, which are explained in the ADVANCED FEATURES section of this
This thermostat can be used with most 24 volt: single-stage heat pumps, and 2-heat / 1-cool heat pump
systems with auxiliary and/or Emergency heat. Second Stage Dual Fuel Systems Capable.
IF YOU FORGET YOUR LOCK CODE: Place the Set Slide Switch in the RUN position, and perform a single
press of the RESET button (located to the left of the DOWN button). The screen will change to become
fully populated with all segments shown. After the screen returns to a normal display, enter the
following four-button sequence, using a single press for each button: UP, UP, UP, DOWN. You should
leave approximately one second between button presses. If the thermostat was already unlocked when
you started this procedure, the screen will remain in the normal run display, and your lock code has
been returned to the default of “0000”. If the thermostat was in a locked state when you started this
procedure, you will see the Enter Unlock Code screen with “1000” shown due to the buttons you
recently pressed. Press DOWN one time so that the display shows “0000”, and press NEXT for at least
4 seconds. The padlock should disappear, and the thermostat should now be unlocked, and showing
the normal run display. When you use this Reset Lock Code procedure, no changes will be made to
other thermostat settings or options.
This thermostat cannot be used to control: conventional heating and cooling systems, 2/3-wire zone
valves, or 120/240 volt (line voltage) heating or cooling systems. Ask your dealer for other LUXPRO®
thermostats to control those systems.
THERMOSTAT BASIC OPERATION:
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 will start flashing. Use UP or
DOWN to set the time, making sure the AM/PM indication is correct. Holding UP or DOWN will make
the clock digits scroll rapidly. Return the Set Slide Switch to RUN.
TOOLS YOU MAY NEED:
Screwdrivers, wire stripper / cutter, and possibly a drill with assorted bits (new installations only).
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. When
the thermostat is first powered up, it will follow a default temperature routine that is preset from the
factory (shown below).
REMOVAL OF 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.
TEMPERATURE LIMIT STOPS: There are two independent set temperature stops: a maximum heat set
temperature, and a minimum cool set temperature. Each of these temperature stops is user adjustable
in one-degree increments. 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.
2. Remove the front portion of your old 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
MORN 6:00 AM 70 °F (21 °C) 6:00 AM 78 °F (26 °C)
8:00 AM 62 °F (17 °C) 8:00 AM 85 °F (29 °C)
6:00 PM 70 °F (21 °C) 6:00 PM 78 °F (26 °C)
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.
NITE 10:00 PM 62 °F (17 °C) 10:00 PM 82 °F (28 °C)
To set the heat and cool set temperature limit stops, always start with 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, either from OFF to HEAT (to adjust the maximum heat set temperature), or
from OFF to COOL (to adjust the minimum cool set temperature). The words “SET”, and either “LIM
HEAT” or “LIM COOL” will be displayed on the LCD screen while you are setting the heat or cool limits
respectively. While in the adjustment mode for each of the temperature stops, use the UP and DOWN
buttons to adjust the limit value, just as you would for adjusting the set temperature under normal
operation. NOTE: If no buttons are pressed for 4 seconds, the thermostat will accept the limit value
that was on the screen at that time, and return to the normal run screen for the current System Mode
switch position. Once you have adjusted the Set Temperature Limit Stops, you should return to the
adjustment mode again for both heat and cool to confirm your desired limit settings for both
When the thermostat is in Heat mode, the word “HEAT” will be present on the screen. When the
thermostat is calling for your heating system to run, the word “HEAT” will be flashing. If there is a
large thermal demand present which is greater than the first stage of heating can accommodate, then a
second stage of heating (“W2” terminal) will be activated, flashing the word “AUX” and “HEAT” on the
display. When the thermostat is in Cool mode, the word “COOL” will be present on the screen. When
the thermostat is calling for your cooling system to run, the word “COOL” will be flashing.
THERMOSTAT 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.
EMERGENCY HEAT: Moving the System Mode switch to the EMER position will activate Emergency Heat
mode. While in Emergency Heat mode, the words “HEAT” and “AUX” will both be shown in the display
screen. When Emergency Heat is currently running, the word “AUX” will flash on the screen.
Emergency Heat mode will prevent the first stage of your heat pump system from turning on, and use
only the “E” terminal 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.
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: place the Set Slide Switch in the RUN position, and perform
a single press of the RESET button (located to the left of the DOWN button). The screen will change to
become fully populated with all segments shown. After the screen returns to a normal display, enter the
following four-button sequence, using a single press for each button: UP, UP, DOWN, DOWN. You
should leave approximately one second between button presses. The cooling terminal can now be
activated one time without waiting for the delay, and once activated the thermostat will return to normal
run mode with delays present. When you use this Compressor Protection Bypass procedure, no
changes will be made to other thermostat settings or options.
INSTALLATION OF NEW THERMOSTAT:
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
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).
TEMPERATURE OVERRIDE: While in Program 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 by moving the mode switch to OFF, then back to HEAT or COOL.
FULL SOFTWARE RESET: This complete reset returns all heating and cooling temperature programs, and
all user changeable software options, to their factory default values. It is recommended that you write
down your current heating and cooling program values for reference prior to performing a software
reset. To perform a software reset: move the System Mode switch in the OFF position, and the Set Slide
switch to the RUN position. Perform a single press of the RESET button (located to the left of the
DOWN button). The screen will change to become fully populated with all segments shown. After the
screen returns to a normal display, enter the following four-button sequence, using a single press for
each button: UP, DOWN, UP, DOWN. You should leave approximately one second between button
presses. After the software reset steps have been performed, you will not notice anything different on
the screen, and the thermostat will be ready for normal operation (you may wish to adjust the heating
and cooling programs to suit your temperature preferences).
MINIMUM RUN TIME: The thermostat has an 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 change in set temperature, please wait
5 minutes and the system should resume normal operation.
WIRING TERMINAL CONNECTIONS:
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. To enter Hold mode: press HOLD one time and the word Hold will
appear in the display. To cancel a Hold, press HOLD one more time.
1. 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.
2. Securely tighten all of the electrical terminal screws, including any unused ones. Be careful not to
over tighten the screws, they only need to be snug.
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
(light switch) before touching your thermostat.
** Complete heating and/or cooling system wiring can be found in the WIRE IDENTIFICATION AND
WIRING SCHEMATICS section of this instruction sheet. The schematics shown provide component
information for brand new installations or for unreferenced wires.
LCD DISPLAY BACKLIGHT: The display screen has backlighting that will 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 backlight is on, will reset the timer,
causing the screen to remain illuminated for an additional 10 seconds.
This thermostat is powered by two “AA” Alkaline batteries. The batteries should be replaced AT LEAST
once per year (or sooner, if “LOW BAT” battery symbol appears in the lower left portion of the display
screen). The batteries are located on the back of the circuit board, and can be accessed by pulling the
front portion of the thermostat straight outwards and removing it from the wall. 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 latch
SYSTEM CONFIGURATION AND SETUP OPTIONS:
On the circuit board, there are hardware settings called “jumpers”. Each jumper
has 3 metal pins, and a small black cap. The cap is moved to either the top two
pins or the lower two pins. Changes to these options are recognized every time
the EMER/HEAT/OFF/COOL mode switch is moved.
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: Emergency Heat mode uses the
regular Heat mode temperature programs.
JP1 (CTRL): [UP = Manual Operation] The thermostat operates manually, and
only shows the room and set temperatures. In this mode, there are no
temperature programs, days of the week, or clock times. [DOWN = Program
WEEKDAY PROGRAMS: Move the Set Slide switch to WEEKDAY. You will be programming all five
weekdays at the same time. Use UP or DOWN to adjust the start time for the MORN period, then press
NEXT to advance. Use UP or DOWN to adjust the set temperature for the MORN period, then press
NEXT to advance. Now adjust the start time and set temperature for the DAY period, pressing NEXT
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 you are finished setting all four periods, continue
pressing NEXT to review your entries for all 4 periods. Move the Set Slide switch to the RUN position if
you are finished, or to WEEKEND to adjust the periods for Saturday or Sunday periods.
Operation, default] The thermostat follows four temperature programs: MORN,
DAY, EVE, and NITE. Each period has a start time and a set temperature.
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
questions, and also permits you to email your questions to our technical support staff at your
JP2 (SCALE): [UP = Celsius] This setting displays all temperature values in C˚ degrees. [DOWN =
Fahrenheit, default] All temperature values are displayed in F˚ degrees.
JP3 (BATT): [UP = None] This setting only applies if you are NOT using batteries in the thermostat, and
are powering the thermostat entirely from the system (“C” wire terminal). [DOWN = Batt, default] This
setting, regularly monitors the battery level, and shows “LOW BAT” on the screen if the batteries need
replaced. Use this setting at all times when batteries are physically present in the thermostat.
WEEKEND PROGRAMS: Move the Set Slide switch to WEEKEND. You will be programming both
Saturday and Sunday at the same time. You will begin with the start time for the MORN period, and use
the same steps that you did for setting the Weekday periods, pressing NEXT to advance through the
values. Return the Set Slide switch to the RUN position when you are finished.
JP4 (B/O): [UP = “B”] This setting energizes the “B/O” wire terminal at all times in HEAT mode, and is
not energized in COOL mode. This setting is not typical, and is only needed for certain brands of heat
pump units, such as: Rheem, Ruud, Goettl, and Bard. [DOWN = “O”, default] This setting energizes the
“B/O” wire terminal at all times in COOL mode, and is not energized in HEAT mode. This setting is used
for the majority of heat pump units with the exception of only a few brands.
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.
JP5 (HP MODE): [UP = Dual] Use this setting if you are using a “fossil fuel” type furnace as your
Auxiliary 2nd heat stage (connected to the “W2” terminal). When the 2nd heating stage is called for, the
first heating stage (heat pump “Y” terminal) is de-energized. Types of systems that would typically use
the “Dual” fuel setting would be: natural gas furnace, propane furnace, and oil furnace. [DOWN = Elec,
default] This setting is used for the majority of traditional heat pump applications, which use an electric
heating element as the Auxiliary heat stage, and also as the Emergency heat device (connected to the “E”
terminal) if present. This setting always runs the system’s blower fan (“G” terminal) when heating is
called for, and is usually required for electric heating elements.
TEMPERATURE SWING: The amount of temperature variation between load-on and load-off is changed
by adjusting the swing setting. The default value is #1, and the adjustment range is from #1 to #9.
smaller swing number makes the temperature control more precise and constant, and increases the
number of cycles per hour. A larger swing number will produce a greater variation between load-on and
load-off events, and decreases the number of cycles per hour. To adjust the swing: place the Set Slide
switch in the RUN position, and press both NEXT and HOLD at the same time. Use UP or DOWN to
change the setting, then press NEXT when finished.
TEMPERATURE CALIBRATION: This thermostat is calibrated at the factory and in most cases, alterations
to this setting should not be required. The Calibration feature allows you to manually offset the room
temperature measurement by as much as plus or minus 5°F (3°C) degrees from its original value. 0°F
(0°C) is the default setting. To adjust the Calibration: place the Set Slide Switch in the RUN position,
and the System Mode switch in the OFF position. Press both UP and DOWN together for at least 4
seconds. Use UP or DOWN to change the setting, then press NEXT when finished.
JP6 (FAN): [UP = Gas] This setting lets the heating system control the blower fan automatically by itself.
Types of systems that would typically use the “Gas” fan setting would be: natural gas furnace, propane
furnace, and oil furnace. [DOWN = Electric / HP, default] This setting runs the system’s blower fan when
heat is called for, and is required for systems that do not control their own fan while in HEAT mode.
Heat pump systems, and units with an electric heating element typically require this setting.
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.
2 0 1 2 L U X P R O D U C T S C O R P O R A T I O N . A L L R I G H T S R E S E R V E D