Lennox MERIT Series Installation Instructions Manual page 24

Complete the wiring connections to the equipment. Use
the provided unit wiring and field wiring diagram shown in
figure 30. Use 18-gauge wire or larger that is suitable for
Class II rating for thermostat connections.
WARNING
Electric Shock Hazard. Can cause injury or
death. Unit must be properly grounded in
accordance with national and local codes.
Electrically ground the unit according to local codes or, in
the absence of local codes, according to the current Na-
tional Electric Code (ANSI/NFPA No. 70). A green ground
wire is provided in the field make-up box.
NOTE - The ML180UHE furnace contains electronic com-
ponents that are polarity sensitive. Make sure that the fur-
nace is wired correctly and is properly grounded.
Accessory Terminals See pages 26 and 27 for ignition
control illustration
One line voltage "EAC" 1/4" spade terminal is provided on
the furnace integrated control. See figure 31 for integrated
control configuration. This terminal is energized when the
indoor blower is operating. Any accessory rated up to one
amp can be connected to this terminal with the neutral leg
of the circuit being connected to one of the provided neu-
tral terminals. If an accessory rated at greater than one
amp is connected to this terminal, it is necessary to use
an external relay.
One line voltage "HUM" 1/4" spade terminal is provided
on the furnace integrated control. See figure 31 for inte-
grated control configuration. This terminal is energized
in the heating mode when the combustion air inducer is
operating. Any humidifier rated up to one amp can be con-
nected to this terminal with the neutral leg of the circuit
being connected to one of the provided neutral terminals.If
a humidifier rated at greater than one amp is connected to
this terminal, it is necessary to use an external relay relay.
Model Number
ML180UH045E36A
ML180UH070E36B
ML180UH090E48B
ML180UH090E60C
ML180UH110E60C
ML180UH135E60D
Model Number
All Models Factory Setting
Allowable Heating Speeds
Red Yellow
Not Allowed
Not Allowed
Allowed Allowed
Not Allowed
Not Allowed
Allowable Circulation Speeds
Red Yellow
Not Allowed
One 24V "H" 1/4" spade terminal is provided on the fur-
nace integrated control. See figure 31 for integrated con-
trol configuration. The terminal is energized in the heating
mode when the combustion air inducer is operating and
the pressure switch is closed. Any humidifier rated up to
0.5 amp can be connected to this terminal with the ground
leg of the circuit connected to ground or the "C" terminal.
Generator Use - Voltage Requirements
The following requirements must be kept in mind when
specifying a generator for use with this equipment:
• The furnace requires 120 volts + 10% (Range: 108
volts to 132 volts).
• The furnace operates at 60 Hz + 5% (Range: 57 Hz
to 63 Hz).
• The furnace integrated control requires both po-
larity and proper ground. Both polarity and proper
grounding should be checked before attempting to
operate the furnace on either permanent or tempo-
rary power.
• Generator should have a wave form distortion of
less than 5% total harmonic distortion.
Thermostat
Install the room thermostat according to the instructions
provided with the thermostat. See figure 30 for thermostat
designations. If the furnace is being matched with a heat
pump, refer to the thermostat installation instructions for
set up.
Indoor Blower Speeds
1 - When the thermostat is set to "FAN ON," the indoor
blower will run continuously on the fan speed when
there is no cooling or heating demand. See TABLE
8 for allowable circulation speeds.
2 - When the ML180UHE is running in the heating mode,
the indoor blower will run on the heating speed.See
TABLE 7 for allowable heating speeds.
3 - When there is a cooling demand, the indoor blower
will run on the cooling speed.
TABLE 7
Blue
Factory Setting
TABLE 8
Blue
Not Allowed
Page 24
Brown Black
Allowed
Not Allowed
No Allowed
Brown Black
Not Allowed Not Allowed