Lennox Harmony III Installation Instructions Manual page 5

Install the discharge air temperature probe in the dis-
charge plenum downstream from the cooling coil. Be sure
that the discharge air will pass over the sensor before the
air is distributed into the duct system. A typical upflow fur-
nace probe installation is shown in figure 4.
Discharge Air Temperature Sensor Placement
(Typical Upflow Furnace)
sensor centered in discharge airflow
sensor
sensor
1/3 the
depth of the
plenum
Fasten the probe bracket to the
plenum with two self- tapping
sheet metal screws.
Connect wires to DAS on Zone Control
Board (see figures 19 through 21)
Figure 4
Be sure that the tip of the sensor is located approximately
10 inches from the indoor coil in the discharge plenum, and
1/3 the depth of the plenum, and centered over the dis-
charge airflow, side-to-side.
1/2 the width of the
plenum
discharge plenum
(top view)
plenum
10"
coil
furnace or
blower coil
PLENUM
front
Thermostats
Locate each thermostat in its zone. If two or more rooms
are within a single zone, place the thermostat in a location
that is central to all rooms. For example, if a zone contains
two bedrooms, try to place the thermostat in a hallway near
both bedrooms.
Do not install thermostats in drafty areas, behind doors or
in corners, near radiant heat sources such as appliances
and sunny windows, near concealed pipes and chimneys,
or in unconditioned spaces such as closets or exterior
walls.
Dampers
Motorized dampers in the supply duct system regulate air
to the zones.
IMPORTANT
Up to 5 dampers per zone may be connected in par-
allel to the zone control panel
of six dampers for entire system.
Some applications will be unique and require more than
one damper per zone. If additional dampers are required,
refer to the the wiring diagram in the Common System
Component Wiring section (page 12). Also, if more than 6
dampers are used, another transformer and isolation relay
will be necessary.
For more effective zone isolation, the return duct system
may also be dampered by zone. Dampers for each zone
must be wired in parallel. Install dampers in the desired
locations; then run thermostat wire from the damper to the
zone control board and slave relays as needed.
Transformer
Obtain an appropriately-rated transformer and electrical
junction box (see table 1). Install the transformer in the
electrical junction box near the zone control board.
Pressure Switch (Heat Pump Systems Only)
NOTE − If a pressure switch is factory installed in the unit,
do not remove the switch or switch wires.
Use a saddle valve (3/8" or 1/2") to install the pressure
switch in the discharge line between the compressor and
the reversing valve. The switch may also be fastened di-
rectly to the suction valve service port which becomes the
high side in heat pump mode.
Page 5
not to exceed a total
HARMONY IIIT SERIES