E2008 Lennox Industries Inc.
Dallas, Texas, USA
RETAIN THESE INSTRUCTIONS
FOR FUTURE REFERENCE
Description
The Lennox ComfortSenset 3000 Series model L3021H
non-programmable electronic thermostat is easy-to-use,
has a large, easy-to-read display, and provides excellent
temperature control. The thermostat also includes a pro-
grammable filter change reminder, and a system check in-
dicator which will notify the user of the need for equipment
service.
Thermostat model L3021H is suitable for 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 the Lennox model
L3021H thermostat. Refer to the installation manual for
instructions regarding installation and wiring of the thermo-
stat.
02/08
*2P0208*
OPERATION MANUAL
ComfortSenset 3000 Series
Model No. L3021H
Non-Programmable Thermostat
CONTROLS
506078−01
02/08
Supersedes 504,931M
Table of Contents
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Initial Thermostat Power-up
When power is initially applied to the thermostat, the dis-
play will appear as shown in figure 1.
88
ROOM
SETPOINT
Figure 1. Display − Initial Power−Up
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).
*P506078-01*
Litho U.S.A.
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FILTER
SERVICE
FAN
ON
AUTO
88
SYSTEM
COOL
OFF
EMG.
HEAT
506078−01
1
1
1
1
2
3
3
4
4
4
5
6
6
6
8
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