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8 - An unpowered, normally open (dry) set of contacts
with a 1/4” spade terminal “HUM” are provided for
humidifier connections and may be connected to
24V or 120V. Any humidifier rated up to one amp can
be connected to these terminals. In 120V humidifier
applications the neutral leg of the circuit can be
connected to one of the provided neutral terminals.
This terminal is energized in the heating mode.
9 - Install the room thermostat according to the
instructions provided with the thermostat. See table 8
for field wiring connections in varying applications. If
the furnace is being matched with a heat pump, refer to
the instruction packaged with the dual fuel thermostat.
Thermostat Selection
CAUTION
Field wiring for both communicating and non-
communicating applications is illustrated in diagrams,
which begin on Page 25..
Non-Communicating
In non-communicating applications the SL280UHV
is designed to operate in a SINGLE-STAGE mode or
TWOSTAGE mode using a conventional thermostat.
For optimal performance in non-communicating applica-
tions, Lennox recommends use of a ComfortSense® 7000
high quality electronic digital thermostat or any other with
adjustable settings for 1st stage / 2nd stage on / off differ-
entials and adjustable stage timers.
Lennox recommends the following two-stage thermostat
settings:
First heat stage differential set to 1/2 to 1 degree F; sec-
ond heat stage differential set to 1/2 or 1 degree F; second
heat stage upstage timer disabled, or set to maximum (1
hr minimum).
Communicating
In communicating applications the icomfort Wi-Fi® ther-
mostat must be used. Refer to the instructions provided
with the thermostat for installation, set-up and operation.
In communicating system all unused thermostat wire in
the wire bundle needs to be terminated inside and out.
The extra wires can terminate on the ‘C” terminal of the
icomfort communication terminal strip. (RSBus). Using an
additiona wire come off ”C” terminal and wire nut all the
extra wires together. Termination on the outdoor control
must match the indoor control.
Indoor Blower Speeds
Non-Communicating
1 - When the thermostat is set to “FAN ON,” the indoor
blower will run continuously at a field selectable
percentage of the second-stage cooling speed
when there is no cooling or heating demand. The
factory defaul setting is 38% of cool speed.
2 - When the SL280UHV is running in the heating
mode, the indoor blower will run on the heating
speed designated by the positions of DIP switches
11, 12 and 13. First stage heating will run at 91%
heat speed.
3 - When there is a cooling demand, the indoor blower
will run on the cooling speed designated by the
positions of DIP switches 5 and 6. First stage
cooling will run at 70% cool speed.
Communicating
NOTE - When the SL280UHV is used with icomfort Wi-
Fi® thermostat, proper indoor blower speed selections
are made by the communicating thermostat
.
1 - When the thermostat is set to “FAN ON,” the indoor
blower will run at setting determined during system
configuration.
2 - When there is a heating demand the fan will run on
heating speeds for firing rate.
3 - When there is a cooling demand, the fan will run on
the first stage and second stage cooling speed set
using the icomfort Wi-Fi® thermostat in the installer
setup mode. The factory default is based upon 400
CFM a ton.
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 (Range: 102 volts to 132
volts)
• The furnace operates at 60 Hz + 5% (Range: 57 Hz to
63 Hz)
• The furnace integrated control requires both correct
polarity and proper ground. Both polarity and prop-
er grounding should be checked before attempting to
operate the furnace on either permanent or temporary
power
• Generator should have a wave form distortion of less
than 5% THD (total harmonic distortion)
