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506526-01 Page 31 of 39Issue 1031
High Altitude
The manifold pressure may require adjustment to ensure
proper combustion at higher altitudes. Refer to Table 12 for
manifold pressure and pressure switch change.
Other Unit Adjustments
Primary and Secondary Limits
The primary limit is located on the heating compartment
vestibule panel. The secondary limits (if equipped) are
located in the blower compartment, attached to the back
side of the blower. These auto reset limits are factory set
and require no adjustment.
Flame Rollout Switches
This manually reset switches are located on the top of 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 allowing
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 45 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 the jumper position across the five pins on the
integrated control. The unit is shipped with a factory fan off
delay setting of 90 seconds. The fan off delay affects comfort
and is adjustable 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 deenergized.
Longer off delay settings provide lower return air
temperatures; shorter settings provide higher return air
temperatures. See Figure 37.
HEAT FAN OFF TIME IN SECONDS
Figure 37
Manifold Pressure Settings and Pressure Switch
Table 12
NOTE: A natural to L.P. propane gas changeover kit is necessary to convert this unit. Refer to the changeover kit installation instruction for the conversion procedure.
NOTE: For Altitudes of 7501' - 10,000' call Lennox Technical Support Product Applications.
For Safety, shut unit off and remove manometer as soon
as an accurate reading has been obtained. Take care
to replace pressure tap plug.
IMPORTANT