Lux Products SMART TEMP P621Ua User manual

CAUTIONS AND WARNINGS . . . . . . . . . . 2
SYSTEM COMPATIBILITY . . . . . . . . . . . . 3
FEATURES . . . . . . . . . . . . . . . . . . . . . . . 4
TOOLS YOU MAY NEED. . . . . . . . . . . . . . 4
MOUNTING LOCATION . . . . . . . . . . . . . . 5
REMOVE OLD THERMOSTAT . . . . . . . . . . 5
INSTALL THERMOSTAT BASE . . . . . . . . . 6
WIRING INFORMATION . . . . . . . . . . . . . . 6
WIRING DIAGRAMS . . . . . . . . . . . . . . . . 8
COMPLETE THE INSTALL . . . . . . . . . . . 17
FRONT PANEL ITEMS . . . . . . . . . . . . . . 17
SYSTEM CONFIGURATION AND
SETUP OPTIONS. . . . . . . . . . . . . . . . . . 19
OPERATING INSTRUCTIONS . . . . . . . . . 21
TEMPERATURE PROGRAMS . . . . . . . . . 23
ADVANCED FEATURES . . . . . . . . . . . . . 24
BATTERY REPLACEMENT . . . . . . . . . . . 28
TECHNICAL ASSISTANCE . . . . . . . . . . . 29
LIMITED WARRANTY . . . . . . . . . . . . . . 29
MERCURY NOTICE . . . . . . . . . . . . . . . . 30
WARNING: Use Energizer®or DURACELL® Alkaline Batteries Only.
Energizer®is a registered trademark of Eveready Battery Company, Inc.
DURACELL®is a registered trademark of The Procter & Gamble Company
© 2013 LUX PRODUCTS CORPORATION. ALL RIGHTS RESERVED
P621Ua
SMART TEMP®UNIVERSAL 5/1/1-DAY
PROGRAMMABLE OR NON-PROGRAMMABLE THERMOSTAT
(FOR BOTH CONVENTIONAL AND HEAT PUMP SYSTEMS)
INSTALLATION AND OPERATING INSTRUCTIONS
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.
52137

2
• This thermostat requires batteries to operate and failure or sub-standard
performance of the batteries may impair or prevent the correct operation of
the thermostat. Use Duracell®or Energizer®alkaline batteries ONLY for all
LUXPRO thermostats requiring batteries. BE SURE TO CHANGE THE BATTERIES
AT LEAST ONCE A YEAR, or whenever you see the LO BATT indication on the
screen. Failure to follow these battery instructions could result in property
damage and/or personal injury.
• The electrical rating for this thermostat is 1.5 Amps per terminal, with a
maximum total load of 3.0A for all terminals combined.
• The thermostat contains parts that may wear out through use and are
susceptible to failure if over-loaded or used in a manner other than as
indicated in the documentation.
• Check unoccupied residences regularly to ensure that all systems are
operating properly.
• Check any heating/air-conditioning system including this product before
operation and at regular intervals.
• Electrical interference, static electricity, failure or substandard performance of
batteries, wiring defects in the installation and/or characteristics of the
connected HVAC devices may prevent the system from regulating heating and
cooling as anticipated.
• The thermostat is a sensitive device and dropping the product can cause
damage to critical components. If the product is dropped or shaken violently
during transport or installation then it should be replaced immediately.
• Persons with physical or mental limitations may not be able to promptly
respond to a malfunction of the heating/air-conditioning system.
• All residents should be made aware of the potential in any system for
malfunctions that could cause continuous heating or cooling and should be
familiar with the operation and location of the heating/cooling appliance on/off
switch.
• Read the instruction manual completely before installing the thermostat. You
should consult a qualified HVAC technician or an electrician if you do not fully
understand the installation instructions.
CAUTIONS AND WARNINGS:

SETBACK HOLD
SET
RUN
DAY/TIME
TEMP PROG
AIR FILTER
TEMPERATURE
HEAT
OFF
COOL
FAN
AUTO
ON
EMER
NEXT
HEAT
TU
D
AY
S ET
L EFT
FAN
F ILTER
%
P
LCD Display Screen
P621Ua
UP / DOWN Buttons
Set Slide
Switch
Fan Mode
Switch
System Mode
Switch
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.
SYSTEM COMPATIBILITY:
3

• 1 or 2-Heat / 1-Cool, 5/1/1-day programming
• Universal Compatibility for all system types
• Weekdays, Saturday, and Sunday can be programmed separately
• Exclusive LUX®Speed SlideTM for easy programming
• User-selectable periods per day (2 or 4)
• User-selectable programmable or non-programmable operation
• LuxLight®EL (Electro-Luminescent) lighted display
• Programmable air filter life timer
• Graphical filter monitor
• Keypad lockout for unauthorized users
• Manual temperature hold
• Adjustable vacation hold (1 to 30 days)
• Temporary temperature override
• Adjustable temperature differential / cycle-rate
• Adjustable 2nd heat stage Offset setting
• User temperature calibration
• Adjustable heat/cool set temperature limit stops
• Smart recovery
• Dual-powered (battery and/or 24-volt system powered)
• Battery-free memory storage
• F/C temperature display
• 12/24-hour clock display
• 5/2-minute selectable time delay for equipment protection
• Screwdrivers
• Wire Stripper
• Wire Cutter
• Drill with assorted drill bits (new installations only)
TOOLS YOU MAY NEED:
FEATURES:
4

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.
1. Turn OFF the electricity to all heating and cooling
components. Do not turn the electricity back on until
all work is completed.
2. Remove the front portion of your old thermostat to
expose the wiring connections.
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.
REMOVE OLD THERMOSTAT:
MOUNTING LOCATION:
OFF
5

1. Strip wire insulation leaving only 3/8 in. (9.5mm) bare wire ends, and clean off
any corrosion present.
2. Fill the wall opening with non-combustible insulation to prevent drafts from
affecting the thermostat’s normal operation.
3. Separate new thermostat housing using your thumb and index finger. Provide
pressure in opposite directions to the release tabs on the top of the housing,
in the directions shown in the diagram shown above.
4. Route the wires through the opening in the new thermostat base plate, and
hold the base against the wall. Try to line up the screw holes from the prior
thermostat, and install the mounting screws.
5. If the previous holes cannot be used, hold the thermostat base against the
wall so that it appears straight and level (position the base for best
appearance) and mark for the new screw holes. Attach the base to the wall
using the screws provided (use the supplied plastic anchors if needed when
mounting to a soft material such as drywall).
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 INFORMATION:
6
INSTALL THERMOSTAT BASE:
THERMOSTAT TOP VIEW

WIRING DIAGRAM NOTES:
(Important, please read all notes before connecting wires)
• If the information provided in the following wiring diagrams does not clearly
represent or match your system, please refer to the “TECHNICAL ASSISTANCE”
section of this manual, and contact us before removing any of your existing
thermostat wiring.
• All of the dashed wires shown in the wiring diagrams are either optional, or
their usage depends upon your specific system type or brand. For example:
Diagram #1 shows the fan wire as optional. If your system does not have a
fan, than this terminal will not be used.
• Terminal letters shown in black represent typical wiring applications.
Depending upon the brand of your specific system or thermostat, your terminal
letters may not match exactly. Terminal letters shown in gray represent other
possible wiring designations that you might see on your existing thermostat
terminals.
• The optional “C” terminal is used for powering the thermostat by the 24-volt
system, using the System Common wire. This can be used alone, or in
addition to installing batteries as a backup. NOTE: connecting the System
Common wire to the thermostat is not necessary for heating and cooling to
function properly.
• If your old thermostat has both a “Y” and “C” wire both present, then “C” is
most likely a System Common wire.
• For Heat Pump systems, you will use either the “O” terminal or the “B”
terminal on this thermostat, but not both. If your old thermostat has both an
“O” and a “B” wire present, then “B” is likely a System Common wire and may
be connected to the “C” terminal. Connecting a System Common wire to this
thermostat’s “B” terminal may damage the thermostat, and also your heating
and cooling system.
• Some Heat Pump systems have a wire for AUX electric heat (usually W2), and
also a separate wire for Emergency electric heat (usually E). This thermostat
uses the W2 terminal for both AUX and Emergency Heat. Tape off your “E”
wire, and confirm that all components function without it.
• If replacing an old thermostat that has a mechanical clock, there may be two
wires labeled as “C” for the clock power. Tape off these wires and do not
connect them to the “C” terminal of this thermostat.
7

8
#1 CONVENTIONAL: HEATING ............................................................9
1-STAGE OR 2-STAGE
2, 3, 4, 5 WIRES
#2 CONVENTIONAL: HEATING ..........................................................10
3-WIRE ZONE VALVE
3, 4 WIRES
#3 CONVENTIONAL: COOLING ..........................................................11
1-STAGE
3, 4 WIRES
#4 CONVENTIONAL: HEATING AND COOLING .....................................12
1-STAGE HEAT
4, 5 WIRES
#5 CONVENTIONAL: HEATING AND COOLING .....................................13
2-STAGE HEAT
5, 6 WIRES
#6 CONVENTIONAL: HEATING AND COOLING .....................................14
TWO-TRANSFORMERS
5, 6 WIRES
#7 HEAT PUMP: HEATING AND COOLING .....................................15
SINGLE-STAGE ONLY
4, 5 WIRES
#8 HEAT PUMP: HEATING AND COOLING .....................................16
WITH AUX / EMERGENCY HEAT
5, 6 WIRES
DIAGRAM SYSTEM TYPE / DESCRIPTION PAGE #
WIRING DIAGRAMS:

NOTE: THE BLACK TERMINAL LETTERS ARE TYPICAL, GRAY TERMINAL LETTERS ARE BRAND SPECIFIC
W1
4
W
XF
G
B*
W2
RH
V
R
W1 A W2O B CG Y RC RH
1-STAGE OR 2-STAGE, HEATING ONLY
(INCLUDING MILLIVOLT) (2-WIRE HEAT USE “RH” & “W1”)
Factory RH-RC Jumper Wire Installed
#12, 3, 4, 5 WIRES
C
HEATER
STAGE
1
STAGE
2
FAN SYSTEM 24V
TRANSFORMER
SYSTEM COMMON
FAN WIRE
MAY NOT BE
PRESENT IN
ALL SYSTEMS
O
P
T
I
O N
A
L
9

NOTE: THE BLACK TERMINAL LETTERS ARE TYPICAL, GRAY TERMINAL LETTERS ARE BRAND SPECIFIC
X
B*
C
RH
V
R
W1
4
W A
W1 A W2O B CG Y RC RH
HOT WATER HEATING ONLY
(WITH A 3-WIRE ZONE VALVE)
Factory RH-RC Jumper Wire Installed
#23, 4 WIRES
SYSTEM 24V
TRANSFORMER
SYSTEM COMMON
OPEN = Heat On CLOSE = Heat Off
3-WIRE ZONE VALVE
OPEN CLOSE
O
P
T
I
O N
A
L
10

NOTE: THE BLACK TERMINAL LETTERS ARE TYPICAL, GRAY TERMINAL LETTERS ARE BRAND SPECIFIC
XF
G
Y1
6
Y
B*
RC
V
R
W1 A W2O B CG Y RC RH
1-STAGE, COOLING ONLY
Factory RH-RC Jumper Wire Installed
#3
C
FAN SYSTEM 24V
TRANSFORMER
SYSTEM COMMON
3, 4 WIRES
O
P
T
I
O N
A
L
AIR
CONDITIONER
11

NOTE: THE BLACK TERMINAL LETTERS ARE TYPICAL, GRAY TERMINAL LETTERS ARE BRAND SPECIFIC
RH
RC
V
R
Y1
6
Y
F
G
XW1
4
W
B*
W1 A W2 CGO BYRC RH
CONVENTIONAL (NON HEAT PUMP)
1-STAGE HEATING AND 1-STAGE COOLING
Factory RH-RC Jumper Wire Installed
#4
C
FAN SYSTEM 24V
TRANSFORMER
SYSTEM COMMON
HEATER
AIR
CONDITIONER
4, 5 WIRES
O
P
T
I
O N
A
L
12

NOTE: THE BLACK TERMINAL LETTERS ARE TYPICAL, GRAY TERMINAL LETTERS ARE BRAND SPECIFIC
W2
RH
RC
V
R
Y1
6
Y
F
G
XW1
4
W
B*
W1 A W2 CGO BYRC RH
CONVENTIONAL (NON HEAT PUMP)
2-STAGE HEATING AND 1-STAGE COOLING
Factory RH-RC Jumper Wire Installed
#5
C
FAN SYSTEM 24V
TRANSFORMER
SYSTEM COMMON
AIR
CONDITIONER
5, 6 WIRES
O
P
T
I
O N
A
L
HEATER
STAGE
1
STAGE
2
13

NOTE: THE BLACK TERMINAL LETTERS ARE TYPICAL, GRAY TERMINAL LETTERS ARE BRAND SPECIFIC
X
B*
C
R V
RH
R V
RC
Y1
6
Y
F
G
W1
4
W
W1 A W2O B CG Y RC RH
CONVENTIONAL (NON HEAT PUMP) 1-STAGE HEATING AND
1-STAGE COOLING WITH TWO SEPARATE 24V TRANSFORMERS
Factory RH-RC Jumper Wire REMOVED
#6
FAN HEAT 24V
TRANSFORMER
COOL 24V
TRANSFORMER
SYSTEM COMMON
HEATER
AIR
CONDITIONER
5, 6 WIRES
O
P
T
I
O N
A
L
14

NOTE: THE BLACK TERMINAL LETTERS ARE TYPICAL, GRAY TERMINAL LETTERS ARE BRAND SPECIFIC
O
XF
G
Y1
6
Y
B*
RC
V
R
W1 A W2O B CG Y RC RH
SINGLE-STAGE HEAT PUMP SYSTEM
WITH NO AUX OR EMERGENCY HEAT
#7
C
FAN SYSTEM 24V
TRANSFORMER
SYSTEM COMMON
4, 5 WIRES
O
P
T
I
O N
A
L
HEAT PUMP
REVERSING
VALVE
** Use “O” or “B”
Terminals, Never Both CUSTOMER INSTALLED Y-W1 Jumper Wire
Factory RH-RC Jumper Wire Installed
15

NOTE: THE BLACK TERMINAL LETTERS ARE TYPICAL, GRAY TERMINAL LETTERS ARE BRAND SPECIFIC
CUSTOMER INSTALLED Y-W1 Jumper Wire
X
B*
C
W3
W
W2
O
F
G
Y1
6
Y
RC
V
R
W1 A W2O B CG Y RC RH
2-HEAT / 1-COOL, HEAT PUMP SYSTEM
WITH AUX AND EMERGENCY HEAT
Factory RH-RC Jumper Wire Installed
#8
FAN SYSTEM 24V
TRANSFORMER
SYSTEM COMMON
5, 6 WIRES
HEAT PUMP
REVERSING
VALVE
** Use “O” or “B”
Terminals, Never Both
AUX / EMERG.
HEAT
O
P
T
I
O N
A
L
16

INSTALL BATTERIES INTO THERMOSTAT: Install two brand new Energizer®or
DURACELL®“AA” size alkaline (only) batteries, into the thermostat’s battery
compartment. Ensure the batteries are installed in the proper direction.
GAS / ELEC CIRCUIT BOARD OPTION (“G” TERMINAL FAN OPERATION): This
setting is a plastic shorting cap called a jumper. This jumper must remain
installed, and set to either GAS or ELECTRIC for your system to work properly.
This setting changes how your system’s blower fan (if applicable) is controlled
while the thermostat is in HEAT or EMERG HEAT mode, when the Fan switch in
the AUTO position. This setting does not affect the fan operation while in COOL
mode.
When set to “GAS”, the blower fan is controlled
solely by the heating system itself. Systems that
would typically use the “GAS” setting would be:
natural gas, propane, or oil furnaces, and boilers.
NOTE: If your blower fan does not operate properly
after installation, move the Gas / Electric option to
the “Electric” setting.
When set to “ELEC”, the blower fan is controlled
directly by the thermostat. This setting is required
for heating systems that do not control their own
fan, such as HEAT PUMPS, and units that only have
an electric-resistive heating element as the heat
source.
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
17
COMPLETE THE INSTALL:
ELEC
GAS
JP1
BATTERY
FRONT PANEL ITEMS:

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.
SETBACK BUTTON: This button activates and deactivates the SETBACK feature,
which overrides the set temperature for an adjustable duration. This feature is
described in greater detail in the ADVANCED FEATURES section.
UP / DOWN BUTTONS: The UP and DOWN buttons are used to adjust any item
that can be changed by the user. Examples are the set temperatures, clock
times, and days of the week. In many cases, an item may be flashing if it can
currently be adjusted.
HOLD BUTTON: This button activates and deactivates the manual Temperature
Hold feature.
EMER BUTTON: When in Normal Run mode, the usage of this button varies
depending upon your specific system configuration. For heat pump systems,
pressing this button enables your emergency heat function, which is described in
greater detail in the OPERATING INSTRUCTIONS section. For conventional
systems, there is no such thing as emergency heat, so this button will have no
effect.
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.
18

Setup options for how the thermostat will function, along with choosing your
particular system type, are performed using a menu on the display screen.
TO ACCESS THE SETUP MENU: Move the System Mode switch into the OFF
position, and then hold down the EMER button for approximately 5 seconds until
the screen changes. The menu will always start with item #1, and is advanced to
each following item by a single press of the NEXT button. The options for each
item are changed using the UP or DOWN buttons.
ITEM #01 (CLK = CLOCK FORMAT): [12Hr, default] This displays the clock times
using standard AM and PM values. [24Hr] This displays the clock times using the
military-time format (example 22:00 hours, without using AM or PM).
ITEM #02 (TMP = TEMPERATURE SCALE): [F, default] Shows all temperature
values in Fahrenheit. [C] Shows all temperature values Celsius.
ITEM #03 (THERMOSTAT TYPE): [PROG, default] Use this setting for following a
daily program routine. [MAN] This setting omits the program routine and
operates as a manual style non-programmable thermostat. This is very basic and
only shows the room temperature and set temperature on the screen, with no
clock.
ITEM #04 (PERD = PERIOD QUANTITY): [4P, default] Thermostat uses four
periods per day (called MORN, DAY, EVE, and NITE). [2P] The thermostat uses two
periods per day (called DAY and NITE).
ITEM #05 (RCV = EARLY RECOVERY): [OFF, default] Program Set Temperature
values start to occur at exactly the period start times. [ON] Early Recovery
affects how the transition occurs when changing from the NITE to the MORN
period, and when changing from the DAY to the EVE period. The thermostat
calculates how long it takes for your home to recover from a setback on a daily
basis, and turns on ahead of time in order to reach the target set point of the
next upcoming program period by the period’s start time. While in a recovery,
the word “RECOV.” will be shown on the display screen.
ITEM #06 (SYSTEM MODE): [FURN, default] This is for the majority of heating
systems that are not Heat Pumps, such as a gas furnace or hot water boiler. [HP]
Use this setting if you have a Heat Pump system, which uses the outdoor unit as
the primary heat source and may also contain an electric heating element as a
backup heat source. When set to “HP”, ensure that you have also set the
Gas/Electric circuit board option to “ELEC”, as described in the “COMPLETE THE
INSTALL” section.
19
SYSTEM CONFIGURATION AND SETUP OPTIONS:

ITEM #07 (DLAY = DELAY TIME): [5, default] Thermostat waits 5 minutes before
turning the system back on after it was last run. This internal delay prevents
rapid cycling and provides equipment protection. The 5 minute setting is fine for
most applications. [2] Same operation as above but reduced to 2 minutes
between state changes.
ITEM #08, #09, #10 (CYCL = SYSTEM CYCLE DURATION): These three settings
will control how frequently your heating/cooling system will be allowed to cycle
ON during room temperature control. The possible setting values for these three
items are: 60, 30, 20, 15, 12, 10, 8, and 6. Whether all three of these items are
shown, and their available values, will change depending upon what type of
heating system you have selected previously in ITEM #06.
#08 = HEAT MODE, CYCLE DURATION
#09 = COOL MODE, CYCLE DURATION
#10 = EMERGENCY HEAT, CYCLE DURATION
When the heating/cooling system turns on, it will remain running for as long as
necessary to reach and maintain your target set temperature. EXAMPLE: with an
ITEM #08 HEAT CYCLE setting of 12, the heating system will turn on
approximately 5 times per hour (turning ON once every 12 minutes). With an
ITEM #09 COOL CYCLE setting of 20, the cooling system will turn on
approximately 3 times per hour (turning ON once every 20 minutes).
ITEM #11 (STAGE-2 OFFSET): [4, default] This setting is adjusted as a number
from 0 to 9. This setting varies how low the room temperature must drop before
the second (auxiliary) heating stage becomes activated, if present. When set to 0
(ZERO), the second heating stage is completely disabled while in regular Heat
mode (however Emergency Heat mode will still function for heat pump
configurations). A lower number will make the second stage turn on sooner, and
will generally provide increased comfort. A larger number will allow a greater
decrease in room temperature to occur before turning on the second heating
stage, and will generally provide greater energy efficiency. If you find that the
second heating stage is cycling too frequently, use a larger number for this
setting.
20