Auto − Using The Autochangeover Mode; Hold − Temperature Hold Mode; Prog − Thermostat Programming - Lennox Merit 51M37 Operation Manual

NOTE − If no buttons are pressed during a demand for
cooling, the equipment must operate for at least 4 minutes.
After a demand has been satisfied, cooling equipment op-
eration is locked out for 5 minutes. If another cooling de-
mand occurs during this 5−minute interval, COOL" and the
snowflakes will flash; however, the cooling equipment will
not operate until the 5−minute delay has elapsed.
AUTO − Using the Autochangeover Mode
When in either heat mode or cool mode, autochangeover
can be enabled or disabled by pressing the AUTO button. If
enabled, AUTO appears at the lower right corner of the dis-
play. The thermostat will then automatically change over
from heating to cooling and vice versa, to keep the room
temperature in between the heating and cooling setpoints.
Autochangeover can be used in either of the thermostat
hold modes, or when the thermostat program is running.
These modes are described later.
HOLD − Using Temperature Hold Modes
When HOLD is displayed at the HOME screen, the ther-
mostat is in a temperature hold condition. This means that
the temperature program data is ignored and the thermo-
stat functions much like a non−programmable thermostat.
Adjusting Temperature Setpoint in Hold Mode
The temperature setpoint represents the desired tempera-
ture of the space around the thermostat. The default heat
setpoint in hold mode is 70°F; the default cool setpoint in
hold mode is 78°F.
Hold Temperature Mode
i0:30
78
80
70
Figure 9
To adjust the setpoint, press the UP or DOWN (YB) arrow
buttons; the existing setpoint is displayed to the right of the
actual room temperature. Each button press adjusts the
setpoint up or down by 1 degree.
505068M 07/05
Heat Cool
Prog Auto
Copy Day/Time
Fan Hold
(DOOR
OPEN)
Settings Enter
(Outside)
After the desired setpoint is reached, the HOME screen
will reappear after about 15 seconds.
Permanent Hold Mode
At any time the program is running, from the HOME
screen, set a permanent hold (program override) by press-
ing the HOLD button (see figure 9). The thermostat now
functions much like a non−programmable thermostat. Use
the Up/Down arrow buttons to adjust the hold setpoint. To
return to the program, press the HOLD button again.
Temporary (2-Hour) Hold
At any time the program is running, from the HOME
screen, set a temporary 2-hour hold by pressing the Up/
Down arrow buttons until the desired setpoint is displayed;
HOLD" flashes (see figure 10). This overrides the pro-
gram for 2 hours from the last button press, then returns to
the program.
While in Temporary Hold, press the HOLD button once to
switch to Permanent Hold (HOLD displays solid; PROG
not displayed); press the HOLD button again to return to
the program (PROG displays; HOLD not displayed).
Temporary Hold Temperature Mode
i0:30
70
72
68
PROG − Thermostat Programming
The 51M39 thermostat can be programmed to perform a
set of both heating and cooling events for each day of the
week. Each day can be programmed for 4 unique events
per day, and each day can be different from any other day.
To Set Program Events and Temperatures
Figure 11 gives an example of how up to 7 different pro-
grams can be set. Programs A and C reflect the desired
warmth while the home IS occupied (72°); B allows less
heating while the home is NOT occupied; D reflects a cool
sleeping temperature.
NOTE − This example shows heat setpoints; a similar pro-
gram may be set for cool setpoints.
Page 4
Heat Cool
Prog Auto
Copy Day/Time
Fan Hold
Settings Enter
(Outside)
Figure 10
(DOOR
OPEN)