Lennox 51M32 - Manual

This user manual covers the Lennox Merit® Series non-programmable thermostat models 51M32 and 51M33, focusing on their core operational features. The document outlines how to manage heating and cooling modes–including heat and cool activation, demand indicators (such as flame or snowflake icons), and temperature adjustments via arrow keys. It also details fan control settings (continuous vs. auto mode) and filter reminder functionality, including setup and reset procedures. Additionally, it explains technical specifications like measurement accuracy, setpoint ranges, and system protection features, alongside troubleshooting guidance for indicators such as the service or balance point settings.

Page 1 – Introduction and Initial Power-up Display
Page 2 – Controlling Heat Mode
Page 3 – Heating and Cooling Control
Page 4 – Fan Control and Filter Reminder
Page 5 – Service, Reset, and Technical Specifications
Page 6 – Operational Features and Output States
Page 7 – Thermostat Features and Guidelines
Page 8 – Heat Mode Management
Page 9 – Heating and Cooling Demand Control
Page 10 – Fan Mode and Filter Settings
Page 11 – Balance Point and Reset Procedure
Page 12 – Default Settings and Electrical Specifications
Page 13 – Operational Conditions and Backlight Behavior
Page 14 – Backup Heating System Output States

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Page 1

2003 Lennox Industries Inc.

Dallas, Texas, USA

OPERATION
MANUAL

Merit

Series Thermostat

The Lennox Merit

Series Thermostat 51M32 is a nonpro-

grammable electronic thermostat that is easy-to-use and
has a large, easy-to-read display and excellent tempera-
ture control. The thermostat also includes a programmable
filter change reminder and a system check indicator. The
system check indicator will notify the user of the need for
equipment service.
Thermostat 51M32 is suitable for non-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 Lennox thermostat
51M32. Refer to the installation manual for instructions re-
garding installation and wiring of the thermostat.

Initial Thermostat Power-up

When power is initially applied to the thermostat, the dis-
play will appear as shown in figure 1.

Litho U.S.A.

Merit

Series Thermostat

CONTROLS (51M32)

504,865M
09/04

RETAIN THESE INSTRUCTIONS

FOR FUTURE REFERENCE

Table of Contents

Merit

Series Thermostat

. . . . . . . . . . . . . . . . . . . . . .

General

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Introduction

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Initial Thermostat Power-up

. . . . . . . . . . . . . . . . . . . . . .

Heating Control

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Cooling Control

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Adjusting Temperature Setpoint

. . . . . . . . . . . . . . . . . .

Fan Control

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Filter Reminder

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Service Indicator

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Thermostat Reset

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Default Thermostat Settings

. . . . . . . . . . . . . . . . . . . . .

Technical Specifications

. . . . . . . . . . . . . . . . . . . . . . . . .

Thermostat Output Table

. . . . . . . . . . . . . . . . . . . . . . . .

Display − Initial Power−Up

Figure 1

ROOM

SETPOINT

FILTER

SERVICE

FAN
ON
AUTO

SYSTEM
COOL
OFF

EMG.
HEAT

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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About this manual

Brand: Lennox
Model: 51M32
Document type: Manual
Language(s): English
Pages: 14
File size: 165.5 KB
Format: PDF

Summary

Page 1 - Introduction and Initial Power-up Display

Overview of the non-programmable electronic thermostat, display features, table of contents, and initial power-up screen appearance.

Page 2 - Controlling Heat Mode

Instructions for enabling and disabling heat mode, display changes when heat is active or disabled, and location and function of the HEAT button.

Page 3 - Heating and Cooling Control

Methods for controlling heating and cooling modes, interpreting demand indicators (flame/snowflake), adjusting the temperature setpoint using arrow keys, and display figures.