Lennox International Inc 51M37 operation manual Auto − Using the Autochangeover Mode

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,

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
		Heat	Cool
	i0:30	Prog	Auto
	78	Copy Day/Time
80	70	Fan	Hold	(DOOR
				OPEN)
		Settings Enter
			(Outside)

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.

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; 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
		Heat	Cool
	i0:30	Prog	Auto
	70	Copy Day/Time
72	68	Fan	Hold	(DOOR
				OPEN)
		Settings Enter
			(Outside)

Figure 10

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

505068M 07/05