Lennox 51M34 5/2 - User Manual

To Next Page

08/07 505,048M

*2P0807* *P505048M*

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.

OPERATION

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

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 dis-

play will appear as shown in figure 1.

FAN

AUTO

SYSTEM

COOL

OFF

EMG.

HEAT

I8:88

ROOM

MO TU WE TH FR SA SU

SETPOINT

SERVICE

FILTER

MAINT

PROG A | B | C | D HOLD

Figure 1. Initial Power−Up Display

All display segments are momentarily activated. This oc-

curs 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 initializa-

tion time, the actual room temperature will be displayed.

Litho U.S.A.

Need help?

Do you have a question about the Lennox 51M34 5/2 and is the answer not in the manual?

Summary

General

Initial Thermostat Power-up

Details the initial display and sequence upon applying power to the thermostat.

Buttons, Backlight, Timers & Settings

DAY;TIME - Setting the Day and Time

Step-by-step instructions for setting the current day of the week and time.

HEAT - Using the Heat Mode

Enabling and Disabling Heat Mode

Instructions on how to activate or deactivate the heat mode on the thermostat.

PROG - Thermostat Programming

To Set Program Events and Temperatures

Guide to setting specific program events and temperatures for heating and cooling.

SETTINGS - Filter;Maintenance Reminders

Filter and Maintenance Reminders

Instructions on setting up reminders for filter changes and routine maintenance.

The Lennox 51M34 is a 5/2 Day Programmable Thermostat designed for residential heating and cooling systems. It features a large, easy-to-read display and provides excellent temperature control. This electronic thermostat is suitable for non-heat pump, single-stage heat/single-stage cool applications with either gas or electric furnaces.

Function Description:

The primary function of the 51M34 thermostat is to allow users to program heating and cooling schedules for their home. It supports a 5/2 day programming scheme, meaning users can set one schedule for five consecutive days (typically Monday through Friday) and a different schedule for the remaining two days (typically Saturday and Sunday). Each day can have up to four unique events (periods A, B, C, and D) with specific time and temperature setpoints.

The thermostat operates in two main modes: HEAT and COOL. Users can enable or disable these modes using dedicated buttons. In HEAT mode, the thermostat activates heating equipment when the room temperature falls below the setpoint, indicated by a flame icon. In COOL mode, it activates cooling equipment when the room temperature rises above the setpoint, indicated by flashing snowflake icons.

A "HOLD" feature allows users to override the programmed schedule. A permanent hold maintains a set temperature indefinitely, effectively turning the thermostat into a non-programmable device. A temporary 2-hour hold allows for a temporary temperature adjustment before reverting to the programmed schedule.

The fan operation can be set to "AUTO" or "ON." In AUTO mode, the fan runs only when the heating or cooling equipment is active. In ON mode, the fan runs continuously, regardless of equipment operation.

Important Technical Specifications:

Thermostat Type: Electronic programmable thermostat for 1-Stage-Heat/1-Stage Cool, gas or electric heat, non-heat pump, non-power robbing applications.
Power Supply Range: 18VAC - 30VAC (24VAC nominal), 60Hz.
Temperature Display Scale: Fahrenheit or Celsius (user selectable via DIP switch).
Temperature Display Range: 35°F (2°C) to 99°F (37°C).
Temperature Display Resolution: 1°F (1°C).
Temperature Display Accuracy: +/-1°F.
Temperature Setpoint Range: 50°F (10°C) to 90°F (32°C).
Temperature Setpoint Resolution: 1°F (1°C).
Temperature Measurement Range: 35°F to 99°F.
Temperature Measurement Resolution: 0.5°F.
Temperature Measurement Accuracy: +/-1°F.
Field Offset: Adjustable via DIP switches to +/-3°F.
Sampling Method: Temperature measurements sampled every 15 seconds; displayed temperature is the average of the last four measurements.
I/O Relays: All thermostat relays are latching type to minimize power consumption.
Equipment Protection Timers:
- Minimum Compressor OFF time: 5 minutes.
- Minimum Compressor ON time: 4 minutes.
- Minimum Furnace ON time: 3 minutes.
- Minimum furnace cycle time: 6 minutes.
- Minimum compressor cycle time: 6 minutes.
Over-Temperature Protection: Thermal-mechanical switch opens W1 at 93°F+/-6°F.
Operating Conditions: 35°F to 105°F, 5% to 90% RH.
Storage Conditions: -40°F to 185°F, 5% to 95% RH.
Power Loss/Recovery: Memory retained for a minimum of 24 hours during a power loss. After 24 hours, programmed settings revert to default. Power must be applied for at least six consecutive hours prior to a power loss for memory retention.

Usage Features:

Easy-to-Read Display: The thermostat features a large display for clear visibility of time, temperature, and system status.
Intuitive Buttons: Buttons for "Prog," "Day/Time," "Fan," "Hold," "Settings," and Up/Down arrows are located behind a small door on the right-hand side.
Backlight: A pale blue display backlight illuminates for 30 seconds each time a button is pressed, aiding visibility in low light.
Smart Setback Recovery (SSR): This feature, enabled via DIP switch #6, allows the thermostat to react to a program event before it occurs, ensuring the desired temperature is reached at the scheduled time, not after. If disabled, the thermostat reacts at the exact time of the event.
Day and Time Setting: Users can easily set the current hour, minute, and day of the week.
Temperature Adjustment: Setpoints can be adjusted in 1-degree increments using the Up/Down arrow buttons.
Fahrenheit/Celsius Selection: The temperature scale can be switched between Fahrenheit and Celsius using a DIP switch.
Equipment Protection Override: Minimum compressor OFF and equipment cycle timers can be overridden by pressing and holding either the HEAT or COOL button for 4 seconds.

Maintenance Features:

Filter Change Reminder: The thermostat includes a programmable filter change reminder. Users can set intervals of Off, 1, 3, 6, or 12 months of fan run time. A "FILTER" indicator is displayed when the programmed time elapses. The reminder can be reset by pressing the SETTINGS button for 4 seconds.
Equipment Maintenance Reminder: An optional maintenance reminder can be set for intervals of Off, 6, or 12 months of chronological time. A "MAINT" indicator is displayed when the programmed time elapses.
Service Indicator: If abnormal equipment operation is detected (e.g., Y1 terminal activated for 5 minutes and L terminal shorted to R or C), a "SERVICE" indicator will flash on the screen, notifying the user that the equipment requires service from a qualified technician.
Thermostat RESET: A recessed RESET button (accessed with a paper clip or small pencil) is available to restore the thermostat to its default factory settings, including all programming and settings. This is useful in cases of electrical disturbances or malfunctions.

The 51M34 thermostat is designed for user convenience and efficient control of heating and cooling systems, incorporating features for programming, hold functions, fan control, and essential maintenance reminders.