506180−01 09/08
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ComfortSenset Model L7742U
Thermostat
Description
The ComfortSenset Model L7742U thermostat is an elec-
tronic 7−day universal multi-stage programmable touch
screen thermostat. It also offers enhanced capabilities
which include humidification measurement and control,
dew point adjustment control, dehumidification measure-
ment and control, Humiditrol
®
Enhanced Dehumidification
Accessory (EDA) capability, and equipment maintenance
reminders. The 24VAC thermostat also features worry−
free memory storage and a menu−driven display. This doc-
ument supports heat pumps or non−heat pump units, with
up to 4 stage heat / 2 stage cool heat pump (2 stages of
heat pump heating and 2 stages of auxiliary backup heat
are provided. Also, 2 stages of emergency heat are pro-
vided).
An optional outdoor temperature sensor (X2658) is re-
quired in applications with Humiditrol
®
EDA.
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.
Dimensions
Screen dimensions: 3−7/16" (87 mm) width x 2−9/16" (65
mm) height
Case dimensions: 5−7/8" (149 mm) width x 4−9/16" (116
mm) height x 1−1/4" (31mm) depth
Features
Outdoor Temperature Sensor (optional)
The outdoor sensor may be required, especially when us-
ing Humiditrol
®
EDA applications. In addition to measuring
and displaying outdoor temperature, the outdoor sensor
provides dew point adjustment and control for all models. If
used with this thermostat, the sensor enables optimal
heating equipment operation via programmable balance
points.
NOTE − The outdoor sensor uses standard thermostat
wiring; it may be wired using two wires of a multi−wire
cable.
When the outdoor sensor is connected, the temperature is
displayed in the information display area (see figure 2).
NOTE − For proper operation of Humiditrol
®
EDA applica-
tions, the outdoor sensor (X2658) MUST be installed.
L" Input
L" input from the equipment is used to notify the user of an
equipment fault by displaying HVAC ERROR DE-
TECTED" when one of the following conditions exist:
S L" terminal is activated with 24VAC and Y1 has been
activated for 5 minutes, OR,
S LSOM error signal is detected on L" input and Y1 has
been activated for 5 minutes.
NOTE − If system is in battery mode, the L terminal is not
functional. The L input is used for diagnostic information
purposes only, it is not intended to provide equipment
protection.
Compressor Short Cycle Protection
A 5−minute compressor short cycle protection timer begins
when a compressor output is de−energized. Also, if a pow-
er loss occurs, the system will go into compressor protec-
tion mode and display WAIT in the display if there is a cool-
ing or compressor heating call.
Display Fields & Touch Screen Points
A. Selection Tab touch fields − Press to select: HOME
(normal display), SCHEDULE (for programming),
OPTIONS (to set alerts, service reminders, and oth-
er user and installer settings).
A
B
C
D
H
J
I
G
F
E
F
Figure 1. Touchscreen active fields
B. MODE − press to cycle through HEAT, COOL, AUTO
(autochangeover), OFF, EM HEAT (emergency
heat).
C. FAN − press to cycle through ON, CIRC (circulate),
AUTO.
D. SCHED (schedule) − press to change between ON
and OFF.
E. Displays the room temperature.
F. Displays the current operation SET AT point; if in
AUTOchangeover, both HEAT and COOL setpoints
are identified.
G. Up/down arrow touch fields used for adjusting tem-
perature up or down; if in AUTO (autochangeover)
mode, 2 sets of up down arrows.
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