Other Unit Adjustements - Lennox MERIT Series Installation Instructions Manual

Model
Gas
Input Size
Nat
045
LP/Propane
Nat
070
LP/Propane
Nat
090
LP/Propane
Nat
110
LP/Propane
Nat
135
LP/Propane
Model Input
High Altitude Pressure Switch Kit
Size
045 0-4500 ft
070
110
090 No Change
110
135
NOTE - A natural to L.P. propane gas changeover kit is necessary to convert this unit. Refer to the changeover kit instal-
lation instruction for the conversion procedure.
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 require 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. See TABLE 7 for allowable heating
speeds.
Manifold Pressure Settings at all Altitudes
0 - 2000 ft. 2001 -4500 ft .
3.5 3.2
10.0 10.0
3.5 3.2
10.0 10.0
3.5 3.2
10.0 10.0
3.5 3.5
10.0 10.0
3.5 3.5
10.0 10.0
Pressure Switch and Gas Conversion Kits at all Altitudes
4501-7500 ft 7501-10,000 ft 7501-10,000 ft
80W52 80W51
80W52 80W51
80W52 80W51
80W57 80W52
80W52 80W51
TABLE 12
7501 - 10,000
4501 - 7500 ft.
3.0
10.0
2.8
10.0
2.7
9.6
3.0
9.6
2.9
9.6
TABLE 13
High Altitude
Natuarl Gas
Orifice Kit
0-7500 ft
73W37
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 er-
ratic limit operation.
Fan Control
Ignition Control 103217-03
The heat fan-on time of 30 seconds is not adjustable. The
heat fan-off delay (amount of time that the blower oper-
ates 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 de-
lay 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 de-energized. Longer off delay settings
provide lower return air temperatures; shorter settings
provide higher return air temperatures. See figure 33.
Page 30
Line Pressure in. wg.
ft
Min
3.5 4.5
10.0 11.0
3.5 4.5
10.0 11.0
3.5 4.5
10.0 11.0
3.5 4.5
10.0 11.0
3.5 4.5
10.0 11.0
LP/Propane Oricifice Kit
7501-10,000 ft
11K49 11K44
Max
13.0
13.0
13.0
13.0
13.0
13.0
13.0
13.0
13.0
13.0
Natuarl Gas
Orifice Kit
0-7500 ft
73W81