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E2003 Lennox Industries Inc.
Dallas, Texas, USA
MeritR Series Thermostat
The Lennox Merit® Series Thermostat 51M33 is a nonpro- grammable electronic thermostat that is
Thermostat 51M33 is suitable for heat pump, single−stage heat/single cool applications that are matched with a gas or
OPERATION
MANUAL
Merit® Series Thermostat
CONTROLS (51M33)
504,931M
09/04
Litho U.S.A.
RETAIN THESE INSTRUCTIONS |
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FOR FUTURE REFERENCE |
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Table of Contents |
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Merit® Series Thermostat | 1 |
General | 1 |
Introduction | 1 |
Initial Thermostat | 1 |
Heating Control | 2 |
Cooling Control | 3 |
Adjusting Temperature Setpoint | 3 |
Fan Control | 4 |
Filter Reminder | 4 |
Balance Point | 5 |
Service Indicator | 5 |
Thermostat Reset | 5 |
Default Thermostat Settings | 6 |
Technical Specifications | 6 |
Thermostat Output Table | 7 |
Display − Initial Power−Up |
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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 Lennox thermostat 51M33. Refer to the installation manual for instructions re-
ROOM
SETPOINT
88
88
FILTER SERVICE
FAN
ON
AUTO
SYSTEM COOL OFF 
EMG.
HEAT
garding installation and wiring of the thermostat.
Initial Thermostat
When power is initially applied to the thermostat, the dis- play will appear as shown in figure 1.
Figure 1
All display segments are momentarily activated. This oc- curs 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).
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