Filter
Top Products
05/05 505,050M
*2P0505* *P505050M*
Page 1
E2005 Lennox Industries Inc.
Dallas, Texas, USA
RETAIN THESE INSTRUCTIONS
FOR FUTURE REFERENCE
51M37 Merit
®
Series Thermostat
The Lennox Merit
®
Series 5/2 day programmable
electronic thermostat 51M37 provides excellent
temperature control and a large, easy-to-read display. It
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 51M37 is suitable for heat pump, 3-stage heat/2-stage
cool applications using a gas or electric auxiliary heat
source. An optional outdoor temperature sensor provides
auxiliary heat lockout, balance point operation, and
dual−fuel compatibility.
OPERATION
MANUAL
51M37 Merit
®
Series
5/2 Day Programmable Thermostat
CONTROLS
505,050M
05/05
Supersedes 03/05
Table of Contents
51M37 Series 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 4. . . . . . . . . . . . . . . . . . . . . . . . . . . .
HOLD − Temperature Hold Mode 5. . . . . . . . . . . . . . . .
PROG − Thermostat Programming 5. . . . . . . . . . . . . . .
FAN − Controlling Fan Operation 6. . . . . . . . . . . . . . . . .
SETTINGS − Filter and Maintenance Reminders 6. . .
SETTINGS − Balance Point 7. . . . . . . . . . . . . . . . . . . . .
Service Indicator 7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Thermostat RESET 7. . . . . . . . . . . . . . . . . . . . . . . . . . . .
Removing/Installing Thermostat 7. . . . . . . . . . . . . . . . .
Default Thermostat Settings 7. . . . . . . . . . . . . . . . . . . .
Technical Specifications 8. . . . . . . . . . . . . . . . . . . . . . . .
Thermostat Output Table 10. . . . . . . . . . . . . . . . . . . . . . .
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
51M37. 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.
FAN
ON
AUTO
SYSTEM
COOL
OFF
EMG.
HEAT
I8:88
88
Figure 1
AM
PM
ROOM
88
MO TU WE TH FR SA SU
SETPOINT
°
°
Initial Power−Up Display
SERVICE
FILTER
MAINT
Hi
Lo
PROG A | B | C | D HOLD
All display segments are momentarily activated. This oc-
curs as a normal part of thermostat initialization.
Litho U.S.A.