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What is the Harmony IIIt Zone Control Sys-
tem?
Lennox Harmony IIIt Zone Control System manages the
distribution of conditioned air to as many as four specific
areas or zones in the home. The Harmony IIIt control is
an advanced control system that allows a home to be
zoned for heating and cooling without the extra expense of
purchasing two or more HVAC (Heating, Ventilation, and
Air Conditioning) systems.
This control allows the owner to heat or cool occupied
areas, without conditioning unused areas. The system
adapts the HVAC components to provide a balanced and
comfortable environment.
What does the system consist of?
The principle system component is the control center
which acts as the brains" of the Harmony IIIt zone con-
trol system. It coordinates all of the operations of thermo-
stats, motorized dampers, and HVAC equipment.
Harmony IIIt zone control system uses off-the-shelf
1-heat/1-cool, non-power-robbing, non-heat pump elec-
tronic thermostats and motorized dampers with one of the
following Lennox HVAC systems to distribute conditioned
air to zones:
1. Option 1ĊGas Furnace with Variable Speed Blower
Motor (VSM) and either a single- or two-speed con-
densing unit.
2. Option 2ĊBlower coil unit with variable speed blower
motor and either a single- or two-speed heat pump.
3. Option 3ĊGas furnace with variable speed blower
motor and heat pump.
How do I set the control center switches?
The Harmony IIIt control center has only two ON/OFF
switches (see illustration). For the most part, the system
relies on thermostats to provide control of the desired com-
fort level for each zone. The control center also has LEDs
(light emitting diodes) which light to indicate the current op-
erating mode and which zone dampers are closed.
1. Vacation switchĊThe Harmony IIIt control center
operates in either of two modes: central mode (Vaca-
tion switch ON) or zone mode (Vacation switch OFF).
D Central mode (Vacation ON) − all zones receive
conditioned air at the same time (like traditional,
non−zoned HVAC systems). The master thermo-
stat (located in Zone 1) controls any heating or
cooling need for all zones in the building.
D Zone mode (Vacation OFF) − specific zones are
conditioned only when the demand comes from
that zone. Each zone (not necessarily each room)
has its own thermostat. The individual zone ther-
mostats only work when the control center is in
zone mode.