OPERATION
E2007 Lennox Industries Inc.
Dallas, Texas, USA
RETAIN THESE INSTRUCTIONS
FOR FUTURE REFERENCE
51M34 5/2 Day Programmable Thermostat
The Lennox 51M34 5/2 day programmable electronic
thermostat has a large, easy-to-read display and provides
excellent temperature control. This product includes a
programmable filter change reminder, an equipment
maintenance reminder, and a system check indicator to
notify the user when the equipment requires service.
The 51M34 thermostat is suitable for non−heat pump,
single-stage heat/single-stage cool applications with either
gas or electric furnace.
MANUAL
51M34 5/2 Day
Programmable Thermostat
CONTROLS
505,048M
08/07
Supersedes 05/05
Table of Contents
51M34 5/2 Day Programmable Thermostat 1. . . . . . .
General 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Introduction 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Initial Thermostat Power-up 1. . . . . . . . . . . . . . . . . . . . .
Buttons, Backlight, Timers & Settings 2. . . . . . . . . . . .
DAY/TIME − Set Day and Time 2. . . . . . . . . . . . . . . . . .
HEAT − Heat Mode 3. . . . . . . . . . . . . . . . . . . . . . . . . . . .
COOL − Cool Mode 3. . . . . . . . . . . . . . . . . . . . . . . . . . . .
HOLD − Temperature Hold Mode 4. . . . . . . . . . . . . . . .
PROG − Thermostat Programming 4. . . . . . . . . . . . . . .
FAN − Controlling Fan Operation 5. . . . . . . . . . . . . . . . .
SETTINGS − Filter /Maintenance Reminder 5. . . . . . .
Service Indicator 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Thermostat RESET 6. . . . . . . . . . . . . . . . . . . . . . . . . . . .
Removing/Installing Thermostat 6. . . . . . . . . . . . . . . . .
Default Thermostat Settings 6. . . . . . . . . . . . . . . . . . . .
Technical Specifications 7. . . . . . . . . . . . . . . . . . . . . . . .
Thermostat Output Table 8. . . . . . . . . . . . . . . . . . . . . . .
Litho U.S.A.
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 Lennox 51M34
thermostat . Refer to the installation manual for instructions
regarding installation and wiring of the thermostat.
Initial Thermostat Power-up
When power is initially applied to the thermostat, the display will appear as shown in figure 1.
MO TU WE TH FR SA SU
AM
I8:88
PM
PROG A | B | C | D HOLD
ROOM
SETPOINT
°
°
88
Figure 1. Initial Power−Up Display
All display segments are momentarily activated. This occurs as a normal part of thermostat initialization. Within a
few seconds, the Home Screen appears (see figure 2) with
default settings as shown. After about 1 minute of initialization time, the actual room temperature will be displayed.
88
MAINT
FILTER
SERVICE
FAN
ON
AUTO
SYSTEM
COOL
OFF
EMG.
HEAT
Hi
Lo
08/07 505,048M
*2P0807* *P505048M*
MO TU WE TH FR SA SU
AM
I2:00
PM
PROG A B C D HOLD
ROOM
°
MAINT
FILTER
SERVICE
FAN
ON
AUTO
SYSTEM
COOL
OFF
Heat
Prog
Fan
Settings
Cool
Day/Time
Hold
Enter
(DOOR
OPEN)
70
HEAT
Figure 2. Home Screen
At this point, the thermostat will be fully functional; its default temperature setpoint (not shown) is 70°F. At this
point, if the equipment has been fully powered and if a heat
demand were present, the system would begin operating.
NOTE − Temperature scale default is Fahrenheit units but
may be reset to show Celsius, if desired. See page 7.
Buttons, Backlight, Timers & Settings
Buttons are located behind the small door on the right−
hand side of the thermostat (see figure 3).
IMPORTANT
Do NOT begin pressing buttons until after you read
the following section describing each button.
A pale blue display backlight illuminates for 30 seconds
each time any button is pressed.
When PROG or DAY/TIME is pressed, a field begins flashing, expecting another input. Start making changes within
15 seconds or the HOME screen will return.
Figure 3. Thermostat Buttons
When an Arrow, HOLD, HEAT, or COOL button is pressed,
SETPOINT and the temperature setting appears for 15
seconds. If desired, start making changes within 15 seconds or the HOME screen will return. The backlight will
turn off 15 seconds after the HOME screen reappears.
DAY/TIME − Setting the Day and Time
Press the DAY/TIME button and set the CURRENT hour,
minute, and day of week as follows:
1. AM12" will flash on the screen. Press the UP/DOWN
arrows to change the hour. (AM" or PM" must correspond to time of day.) Press DAY/TIME OR, if adjust-
ing for daylight savings time, pressing ENTER stores
the single change and exits to the HOME screen, bypassing minutes and day of week.
2. Minutes will flash. Use the UP/DOWN arrow button to
display the minutes past the hour. Press DAY/TIME.
3. Day MO" (Monday) will flash. Use UP or DOWN arrow
buttons to display the current day. Day selections are
abbreviated as MO, TU", WE", TH", FR", SA",
and SU". Press DAY/TIME.
4. The HOME screen reappears; confirm day and time
are correct. This completes day and time setting.
505048M 08/07
Page 2
HEAT − Using the Heat Mode
COOL − Using the Cool Mode
Enabling and Disabling Heat Mode
The thermostat must be in the HEAT mode to control the
heating equipment. Press the Heat button to enable or disable HEAT mode. If the thermostat is in COOL or OFF
mode, pressing the Heat button enables the HEAT mode
(indicated by HEAT in the SYSTEM box − see figure 4).
Heat
Prog
Fan
Settings
Cool
Day/Time
Hold
Enter
MO
AM
PM
ROOM
66
5:30
HOLD
SETPOINT
°
70
°
FAN
AUTO
SYSTEM
HEAT
Figure 4. Turn Heat ON/OFF
If the thermostat is in heat mode, heat mode is disabled
when the HEAT button is pressed. This is indicated by OFF
in the SYSTEM box as shown in figure 5.
°
SYSTEM
COOL
OFF
HEAT
ROOM
75
°
SETPOINT
75
Figure 5. Heat/Cool Mode Disabled
Heating Demand
Set the thermostat to heat mode to control the heating
equipment. Then, if the room temperature is lower than the
temperature setpoint, as shown in figure 6, the thermostat
detects a heating demand and will activate the heating
equipment to satisfy the demand.
°
SYSTEM
COOL
OFF
HEAT
ROOM
72
°
SETPOINT
75
Figure 6. Heating Demand
Heating operation is indicated by a flame icon in the SYSTEM box. 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 − Heating equipment is activated for at least 3 minutes if no buttons are pressed during the demand interval.
Enabling and Disabling Cool Mode
Use the COOL button to enable or disable cool mode as
desired. If the thermostat is in HEAT or OFF mode, cool
mode is enabled when the COOL button is pressed. This is
indicated by COOL in the SYSTEM box (see figure 7).
Heat
Prog
Fan
Settings
Cool
Day/Time
Hold
Enter
MO
AM
PM
I0:30
ROOM
75
°
HOLD
SETPOINT
70
°
FAN
AUTO
SYSTEM
COOL
Figure 7. Turn Cool ON/OFF
If the thermostat is in cool mode, pressing the Cool button
disables COOL mode (indicated by OFF in the SYSTEM
box − see figure 5).
Cooling Demand
Set the thermostat to cool mode to control the cooling
equipment. Then, if the room temperature is higher than
the temperature setpoint, as shown in figure 8, the thermostat detects a cooling demand and will activate the cooling
equipment to satisfy the demand.
°
SYSTEM
COOL
OFF
HEAT
ROOM
75
SETPOINT
°
70
Figure 8. Cooling Demand
Cooling operation is indicated by flashing snowflake"
icons in the SYSTEM box. When the actual temperature
drops below the temperature setpoint, the snowflake icons
will disappear. This indicates that the cooling demand has
been satisfied and that the cooling equipment has been
turned off.
NOTE − If no buttons are pressed during a demand for
cooling, the equipment must operate for at least 4 minutes.
After a demand has been satisfied, cooling equipment operation is locked out for 5 minutes. If another cooling demand occurs during this 5−minute interval, COOL" and the
snowflakes will flash; however, the cooling equipment will
not operate until the 5−minute delay has elapsed.
Page 3
51M34 5/2 DAY PROGRAMMABLE THERMOSTAT
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