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Lennox MERIT 51M32 Operation Manual

Merit series
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E2003 Lennox Industries Inc.
Dallas, Texas, USA
R
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.
®
OPERATION
MANUAL
®
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
ROOM
SETPOINT
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).
Page 1
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88
SERVICE
FAN
ON
88
AUTO
SYSTEM
COOL
OFF
EMG.
HEAT
Figure 1
Litho U.S.A.
1
1
1
1
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FILTER

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Table of Contents
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  Summary of Contents for Lennox MERIT 51M32

  • Page 1: Merit ® Series Thermostat

    OPERATION ® MANUAL E2003 Lennox Industries Inc. Dallas, Texas, USA ® Merit Series Thermostat CONTROLS (51M32) 504,865M 09/04 Litho U.S.A. RETAIN THESE INSTRUCTIONS FOR FUTURE REFERENCE Table of Contents ® Merit Series Thermostat ..... . General .
  • Page 2: Heating Control

    Display − Home Screen Heat Mode Enabled ROOM ROOM AUTO AUTO SYSTEM SYSTEM SETPOINT HEAT HEAT Figure 2 Figure 4 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 If the thermostat is in heat mode, heat mode is disabled be displayed.
  • Page 3: Cooling Control

    Heating Demand Cooling Demand ROOM ROOM AUTO AUTO SYSTEM SYSTEM COOL HEAT Figure 6 Figure 7 NOTE − The cooling equipment is activated for at least 4 minutes if no buttons are pressed during the demand inter- When the actual temperature rises above the temperature val.
  • Page 4: Fan Control

    Fan Control Filter Reminder The 51M32 thermostat includes a filter reminder feature. The FAN button is located behind the small door on the The filter reminder can be set for 1, 3, 6, or 12−month inter- right-hand side of the thermostat. See figure 3. The FAN vals.
  • Page 5: Balance Point

    Service Indicator Technical Specifications Thermostat Type When abnormal equipment operation is detected, the Electronic nonprogrammable thermostat for 1H/1C, gas or SERVICE indicator will flash on the upper-right corner of electric heat, non−heat pump, non−power robbing applica- the screen. This indicates that the equipment requires ser- tions.
  • Page 6: Thermostat Output Table

    Equipment Protection Override Power Loss/Recovery Thermostat memory is retained for a minimum of 24 hours Both the minimum compressor OFF timer and the mini- during a power loss (includes retention of programmed mum equipment cycle timer can be over−ridden by press- temperature setpoint, heat/cool and fan mode settings, fil- ing and holding either the HEAT or COOL button down for 4 ter reminder status, and equipment protection timers).
  • Page 7: Table Of Contents

    OPERATION ® MANUAL E2003 Lennox Industries Inc. Dallas, Texas, USA ® Merit Series Thermostat CONTROLS (51M33) 504,931M 09/04 Litho U.S.A. RETAIN THESE INSTRUCTIONS FOR FUTURE REFERENCE Table of Contents ® Merit Series Thermostat ..... . General .
  • Page 8 Enabling and Disabling Heat Mode Display − Home Screen Use the HEAT button to select normal heat mode, emer- gency heat mode, or to disable heat modes as desired. If ROOM the thermostat is in off mode, normal heat mode is enabled when the HEAT button is pressed.
  • Page 9: Adjusting Temperature Setpoint

    Enabling and Disabling Cool Mode Heat Mode Disabled Use the COOL button to enable or disable cool mode as necessary. If the thermostat is in off mode, cool mode is en- ROOM abled when the COOL button is pressed. This is indicated by COOL in the SYSTEM box.
  • Page 10 Fan AUTO with Icon Setpoint Display and Adjustment ROOM ROOM AUTO AUTO SYSTEM SYSTEM SETPOINT HEAT HEAT Figure 11 Figure 9 To change from continuous to auto fan mode and vice versa, press the FAN button. Also note the presence of a fan icon in the FAN box.
  • Page 11: Thermostat Reset

    DOWN arrow keys to the right of the display screen. The Display of Filter Reminder balance point setting will increase by 1°F each time the UP key is pressed. The balance point setting will decrease by FILTER ROOM 1°F each time the DOWN key is pressed. After the desired balance point is reached, the HOME screen will reappear after about eight seconds.
  • Page 12: Default Thermostat Settings

    Table 2 Default Thermostat Settings 51M33 Terminal Designations Default Thermostat settings are in table 1. Connections Description Table 1 Reversing valve, cool active Default Thermostat Settings Reversing valve, heat active Mode Heat 24VAC Setpoint 70°F (or 21°C) Fan control Auto First stage cooling/heating, compres- Filter Reminder OFF (reminder setting = 0)
  • Page 13 Service Reminder IMPORTANT The SERVICE indicator is displayed only under the follow- Power must be applied for at least six consecutive ing conditions: hours prior to a power loss in order for memory to be if the thermostat Y1 terminal has been activated retained for the specified time.
  • Page 14 Table 3 Thermostat Output States Condition Electric Heat Backup − No Outdoor Sensor small heat demand large heat demand emergency heat demand cool demand no demand Gas Heat Backup (Dual Fuel) − No Outdoor Sensor small heat demand large heat demand emergency heat demand cool demand no demand...

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Merit series