Lennox MERIT Series Installation Instructions Manual page 34

Refer to FIGURE 53 for field wiring, schematic wiring dia-
gram and troubleshooting.
The power supply wiring must meet Class I restrictions.
Protected by either a fuse or circuit breaker, select circuit
protection and wire size according to unit nameplate.
CAUTION
Failure to use properly sized wiring and circuit breaker
may result in property damage. Size wiring and circuit
breaker(s) per Product Specifications bulletin (EHB) and
unit rating plate.
NOTE - Unit nameplate states maximum current draw.
Maximum Over-Current Protection allowed is 15 AMP.
Holes are on both sides of the furnace cabinet to facilitate
wiring.
Install a separate (properly sized) disconnect switch near
the furnace so that power can be turned off for servicing.
Before connecting the thermostat or the power wiring,
check to make sure the wires will be long enough for ser-
vicing at a later date. Remove the blower access panel to
check the length of the wire.
Complete the wiring connections to the equipment. Use
the provided unitw wiring diagram and the field wiring di-
agram shown in FIGURE 53. Use 18-gauge wire or larger
that is suitable for Class II rating for thermostat connec-
tions.
Electrically ground the unit according to local codes or,
in the absence of local codes, according to the current
National Electric Code (ANSI/NFPA No. 70) for the USA
and current Canadian Electric Code part 1 (CSA standard
C22.1) for Canada. A green ground wire is provided in the
field make-up box.
NOTE - The ML193DFE furnace contains electronic com-
ponents that are polarity sensitive. Make sure that the fur-
nace is wired correctly and is properly grounded.
Accessory Terminals
One line voltage "EAC" 1/4" spade terminal is provided
on the furnace integrated control. See FIGURE 54 for in-
tegrated 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 pro-
vided neutral 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 120V "HUM" 1/4" spade terminal is pro-
vided on the furnace integrated control. See FIGURE 54
for integrated control configuration. This terminal is ener-
gized in the heating mode when the combustion air induc-
er is operating. Any humidifier 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 neutral terminals.
If a humidifier rated at greater than one amp is connected
to this terminal, it is necessary to use an external relay.
One 24V "HUM" 1/4" spade terminal is provided on the
furnace integrated control. See FIGURE 54 for integrat-
ed control configuration. The terminal is energized in the
heating mode when the combustion air inducer is operat-
ing 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.
Thermostat
Install the room thermostat according to the instructions
provided with the thermostat. See FIGURE 53 for thermo-
stat designations. If the furnace is being matched with a
heat pump, refer to the thermostat installation instruction
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 19 on page 48 for allowable continuous
circulation speeds.
2 - When the ML193DFE is running in the heating mode,
the indoor blower will run on the heating speed
(HEAT).
3 - When there is a cooling demand, the indoor blower
will run on the cooling speed (COOL).
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 tem-
porary power Generator should have a wave form
distortion of less than 5% THD (total harmonic dis-
tortion).
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