Other Unit Adjustments - Lennox EL280DF Installation Instructions Manual

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.
1 2
120sec.
1 2
To adjust fan−off timing, flip dip switch to desired setting.
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.
Page 27
90sec.
3 4 5 1 2 3 4 5
180sec.
3 4 5 1 2 3 4 5
FIGURE 23