Other Unit Adjustments; Table 5 - Lennox ML180UHA Installation Instructions Manual

High Altitude
The manifold pressure may require adjustment and com­
bustion air pressure switch may need replacing to ensure
proper combustion at higher altitudes. Refer to table 5 for
manifold pressure and table 6 for pressure switch change
and gas conversion kits.
Model
Gas
Input Size
Nat
All Models
LP/propane
* See table 6 for proper high altitude gas conversion kit.
High Altitude Pressure Switch Kit
Model
Input Size
0-610 m
(0-2000 ft)
070
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 installation 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 re­
quire 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 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
Manifold Pressure Settings at all Altitudes
0-610 m* 611-914 m*
(0-2000 ft) (2001-3000 ft.)
0.87 0.72
2.30 2.30
Pressure Switch and Gas Conversion Kits at all Altitudes
611-1219 m 1220-1981 m
(2001-4000 ft) (4001-6500 ft)
80W51 80W56
80W51 80W56
80W51 80W56
No Change 80W51
IMPORTANT
For safety, shut unit off and remove manometer as
soon as an accurate reading has been obtained.
Take care to replace pressure tap plug.

TABLE 5

915-1219 m* 1220-1524 m*
(3001-4000 ft) (4001-5000 ft.)
0.67 0.62
2.19 2.12
TABLE 6
High Altitude
Natural Gas to LP/Propane
Natural Gas Burner
Gas Change over Kit
Orifice Kit
1525-1981 m 0-1524 m
(5001-6500 ft) (0-5000 ft)
73W37 11K15
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 the jumper position across the five pins on the in­
tegrated control. The unit is shipped with a factory fan-off
delay setting of 60 seconds. The fan-off delay affects com­
fort and is adjustable to satisfy individual applications. Ad­
just the fan-off delay to achieve a supply air temperature
between 32°C and 43°C at the moment that the blower is
de-energized. Longer off delay settings provide lower re­
turn air temperatures; shorter settings provide higher re­
turn air temperatures. See figure 28.
Page 21
Line Pressure
1525-1981 m*
kPa
(5001-6500 ft)
Min
0.87 1.13
2.30 2.75
LP/Propane to
Natural Gas
Change over Kit
1525-1981 m 1-1524 m
(5001-6500 ft) (1-5000 ft)
97W04 96W95
Max
3.23
3.23