Lennox International Inc EL280DF Other Unit Adjustments, Heat FAN-OFF Time in Seconds

Other Unit Adjustments

Primary and Secondary Limits

The primary limit is located on the heating compartment vestibule panel. The secondary limits (if equipped) are lo- cated in the blower compartment, attached to the back side of the blower. These auto reset limits are factory−set and re- quire no adjustment.

Flame Rollout Switches

These manually reset switches are located on the burner box.

Pressure Switch

The pressure switch is located in the heating compartment adjacent to the combustion air inducer. The switch checks for proper combustion air inducer operation before allow- ing ignition trial. The switch is factory−set and requires no adjustment.

Temperature Rise

After the furnace has been started, and supply and return air temperatures have been allowed to stabilize, check the temperature rise. If necessary, adjust the blower speed to maintain the temperature rise within the range shown on the unit nameplate. Increase the blower speed to decrease the temperature. Decrease the blower speed to increase the temperature rise. Failure to adjust the temperature rise may cause erratic limit operation.

Fan Control

The fan−on time of 30 seconds is not adjustable. The heat fan−off delay (amount of time that the blower operates after the heat demand has been satisfied) may be adjusted by changing DIP switches 3 and 4. See figure 23 and table 10. The unit is shipped with a factory fan−off delay setting of 90 seconds. The fan−off delay affects comfort and is adjust- able to satisfy individual applications. Adjust the fan−off delay to achieve a supply air temperature between 90° and 110°F at the moment that the blower is de−energized. Lon- ger off delay settings provide lower return air temperatures; shorter settings provide higher return air temperatures. See figure 23.

HEAT FAN-OFF TIME IN SECONDS

60sec.90sec.

1	2	3	4	5	1		2	3	4	5
	120sec.						180sec.
1	2	3	4	5		1	2	3	4	5

To adjust fan−off timing, flip dip switch to desired setting.

FIGURE 23

Input Voltage Requirements

The circuit is designed to be operated with AC voltage. A voltage of 12 to 33VAC is required to energize the motor. Expected current draw will be less than 20mA.

Blower Speeds

Follow the steps below to change the blower speeds. 1 − Turn off electrical power to furnace.

2 − Remove blower access panel.

3 − Disconnect existing speed tap at integrated control speed terminal.

NOTE − Termination of any unused motor leads must be insulated.

4 − Place unused blower speed tap on integrated control PARK" terminal or insulate.

5 − Refer to blower speed selection chart on unit wiring dia- gram for desired heating or cooling speed. See Blower performance data beginning on the next page.

6 − Connect selected speed tap at integrated control speed terminal.

7 − Resecure blower access panel.

8 − Turn on electrical power to furnace.

9 − Recheck temperature rise. Electronic Ignition

The integrated control has an added feature of an internal Watchguard control. The feature serves as an automatic re- set device for integrated control lockout caused by ignition failure. This type of lockout is usually due to low gas line pressure. After one hour of continuous thermostat demand for heat, the Watchguard will break and remake thermostat demand to the furnace and automatically reset the inte- grated control to begin the ignition sequence.

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