OPERATION MANUAL
E2008 Lennox Industries Inc.
Dallas, Texas, USA
RETAIN THESE INSTRUCTIONS
FOR FUTURE REFERENCE
Description
The Lennox ComfortSenset 3000 Series model L3021H
non-programmable electronic thermostat is easy-to-use,
has a large, easy-to-read display, and provides excellent
temperature control. The thermostat also includes a programmable filter change reminder, and a system check indicator which will notify the user of the need for equipment
service.
Thermostat model L3021H is suitable for heat pump,
single−stage heat/single cool applications that are
matched with a gas or electric furnace.
General
These instructions are intended as a general guide and do
not supersede local codes in any way. Consult authorities
having jurisdiction before installation.
Check equipment for shipping damage. If you find any
damage, immediately contact the last carrier.
Introduction
This document describes the operation of the Lennox model
L3021H thermostat. Refer to the installation manual for
instructions regarding installation and wiring of the thermostat.
ComfortSenset 3000 Series
Model No. L3021H
Non-Programmable Thermostat
CONTROLS
506078−01
02/08
Supersedes 504,931M
Table of Contents
Thermostat 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
General 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Introduction 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Initial Thermostat Power-up 1. . . . . . . . . . . . . . . . . . . . .
Heating Control 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Cooling Control 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Adjusting Temperature Setpoint 3. . . . . . . . . . . . . . . . .
Fan Control 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Filter Reminder 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Balance Point 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Service Indicator 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Thermostat RESET 6. . . . . . . . . . . . . . . . . . . . . . . . . . . .
Default Thermostat Settings 6. . . . . . . . . . . . . . . . . . . .
Technical Specifications 6. . . . . . . . . . . . . . . . . . . . . . . .
Thermostat Output Table 8. . . . . . . . . . . . . . . . . . . . . . .
Initial Thermostat Power-up
When power is initially applied to the thermostat, the display will appear as shown in figure 1.
ROOM
SETPOINT
Figure 1. Display − Initial Power−Up
All display segments are momentarily activated. This occurs as a normal part of thermostat initialization. Within a
few seconds, the display will appear as shown in figure 2
(figure shows temperature in Fahrenheit units).
88
88
FAN
ON
AUTO
SYSTEM
COOL
OFF
EMG.
HEAT
Litho U.S.A.
FILTER
SERVICE
02/08 506078−01
*2P0208* *P506078-01*
ROOM
70
FAN
AUTO
SYSTEM
Enabling and Disabling Heat Mode
Use the HEAT button to select normal heat mode, emergency heat mode, or to disable heat modes as desired. If
the thermostat is in off mode, normal heat mode is enabled
when the HEAT button is pressed. This is indicated by
HEAT in the SYSTEM box as shown in figure 4.
HEAT
Figure 2. Display − Home Screen
Figure 2 illustrates the HOME screen. Note that an indoor
room temperature of 70°F is initially displayed. After about
1 minute of warm−up time, the actual room temperature will
be displayed. HEAT mode is the system default (as indicated in the SYSTEM box at lower right).
A pale blue display backlight turns on each time a key is
pressed; then off 8 seconds after the last key is pressed.
Heating Control
The HEAT button is located behind the small door on the
right−hand side of the thermostat. See figure 3.
ROOM
SETPOINT
Figure 4. Normal Heat Mode Enabled
If the thermostat is in normal heat mode when the HEAT
button is pressed, then emergency heat mode is enabled.
This is indicated by EMG. HEAT in the SYSTEM box as
shown in figure 5.
ROOM
SETPOINT
69
64
69
64
FAN
AUTO
SYSTEM
HEAT
FAN
AUTO
SYSTEM
Figure 3. Additional Thermostat Buttons
Normal Heat Mode
In normal heat mode, both the heat pump and the backup
heat source are used to provide heat. If the thermostat detects that the heat pump is not able to provide enough heat
(as may be the case in very cold weather), then the backup
heat source is activated.
Emergency Heat Mode
In emergency heat mode, only the backup heat source
provides heat the heat pump is disabled. The backup
heat source is activated only when there is a heat demand.
EMG.
HEAT
Figure 5. Emergency Heat Mode Enabled
If the thermostat is in emergency heat mode when the
HEAT button is pressed, then heat modes are disabled.
This is indicated by OFF in the SYSTEM box as shown in
figure 6.
ROOM
SETPOINT
Figure 6. Heat Mode Disabled
69
64
FAN
AUTO
SYSTEM
OFF
506078−01 02/08
Page 2
Heating Demand
The thermostat must be in either normal or emergency
heat mode in order to properly control the heating equipment. When in either heat mode, if the actual temperature is
lower than the temperature setpoint, a heating demand is detected by the thermostat. The thermostat will then activate
the heating equipment to satisfy the demand. Heating operation is indicated by a flame icon in the SYSTEM box as
shown in figure 7.
ROOM
72
FAN
AUTO
The thermostat will then activate the cooling equipment to
satisfy the demand. Cooling operation is indicated by a
snowflake icon in the SYSTEM box as shown in figure 8.
When the actual temperature drops below the temperature
setpoint, the snowflake icon will disappear. This indicates
that the cooling demand has been satisfied and that the
cooling equipment has been turned off.
ROOM
79
FAN
AUTO
SYSTEM
COOL
88
Figure 7. Heating Demand
When the actual temperature rises above the temperature
setpoint, the flame icon will disappear. This indicates that
the heating demand has been satisfied and that the heating equipment has been turned off.
NOTE − The heat pump is activated for at least 4 minutes if
no buttons are pressed during the demand interval. The
backup heat source is activated for at least 3 minutes if no
buttons are pressed during the demand interval.
Heat pump operation is locked out for 5 minutes after a demand has been satisfied. If another heat pump demand
occurs during this 5−minute interval, the flame icon will
flash; however, the heat pump will not run until the 5−minute delay has elapsed.
SYSTEM
HEAT
Cooling Control
The COOL button is located behind the small door on the
right-hand side of the thermostat. See figure 3.
Figure 8. Cooling Demand
NOTE − The cooling equipment is activated for at least 4
minutes if no buttons are pressed during the demand interval. Cooling equipment operation is locked out for 5 minutes after a demand has been satisfied. If another cooling
demand occurs during this 5−minute interval, the snowflake icon will flash; however, the cooling equipment will
not run until the 5−minute delay has elapsed.
Adjusting Temperature Setpoint
The temperature setpoint represents the desired temperature of the space around the thermostat. The default temperature setpoint is 70°F. To adjust the setpoint, press the
UP or DOWN arrow keys to the right of the display screen.
The existing setpoint will be displayed just below the actual
room temperature as shown in figure 9. Use the UP or
DOWN arrow keys to adjust the setpoint up or down. The
setpoint will increase by 1°F each time the UP key is
pressed. The setpoint will decrease by 1°F each time the
DOWN key is pressed.
Enabling and Disabling Cool Mode
Use the COOL button to enable or disable cool mode as
necessary. If the thermostat is in off mode, cool mode is
enabled when the COOL button is pressed. This is indicated by COOL in the SYSTEM box.
If the thermostat is in cool mode, cool mode is disabled
when the COOL button is pressed. This is indicated by
OFF in the SYSTEM box.
Cooling Demand
The thermostat must be in cool mode in order to properly
control the cooling equipment. When in cool mode, if the
room temperature is higher than the temperature setpoint,
a cooling demand is detected by the thermostat.
ROOM
SETPOINT
Figure 9. Setpoint Display and Adjustment
After the desired setpoint is reached, the HOME screen
will reappear after about 8 seconds.
Page 3
69
64
FAN
AUTO
SYSTEM
HEAT
L3021H THERMOSTAT
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