Lennox Harmony III Installation Instructions Manual page 2

The Harmony IIIt zone control system uses off−the−shelf,
single-stage, non-heat pump, non−power-robbing elec-
tronic thermostats and motorized dampers in any of the ap-
plications to distribute conditioned air to different zones.
This control allows conditioning of different zones within a
residence while using a single HVAC system.
The zone control system operates in two modes: central
control (vacation mode) or zone control. LEDs indicate
the current operating mode. Based on a demand from the
central control thermostat, the central control mode allows
the heating and cooling system to condition all of the
zones. In this mode, zone 1 thermostat is designated as
the controlling thermostat; other thermostats are not used.
Residential Zone Control System − Overview of Field Wiring
ZONE 1
THERMOSTAT
(ZONE 1 or CEN-
TRAL CONTROL
thermostat when
in Vacation Mode)
ZONE
DAMPER
POWER
ZONE CONTROL
SYSTEM, THERMO-
STAT AND DAMPER
TRANSFORMER
*ZONE 3
THERMOSTAT
(ZONE)
ZONE
DAMPER
NOTE − Zone 3 and zone 4 not available with single-stage outdoor unit.
LEGEND −
A Five wire low voltage
B Two wire low voltage
C Up to nine wire low voltage
D Two wire low voltage (single-stage condensing unit) 18 ga. minimum
Three wire low voltage (two-stage condensing unit) 18 ga. minimum
Up to seven wire low voltage (single-stage heat pump outdoor unit) 18 ga. minimum
Up to eight wire low voltage (two-stage heat pump outdoor unit) 18 ga. minimum
E Two wire low voltage (discharge air sensor) 18 ga. minimum
F Two wire low voltage
G Two wire 18 ga. minimum
505023M 04/06
A
B
ZONE
CONTROL
SYSTEM
BOARD
B
A
B
18 ga. minimum
18 ga. minimum
18 ga. minimum
pressure switch (heat pump only)
When the system is in the zone control mode, a zone is
conditioned only upon demand. All wiring connections to
the zone control board are made using low voltage, 18
AWG thermostat wire.
The zone control system is ideal for retrofit applications as
well as new construction. The system controls the air vol-
ume, eliminating the need for bypass dampers in most ap-
plications. The homeowner controls the system using
zone thermostats to make comfort settings for each zone.
A programmable thermostat should be used to provide a
specialized heating and cooling sequence. While the sys-
tem is in the zone mode, a programmable thermostat con-
trols the temperature for its particular zone.
COIL
E
C
VARIABLE
SPEED
FURNACE
OR COIL
BLOWER
D
B
G
18 ga. minimum
Page 2
A
ZONE 2
THERMOSTAT
(ZONE)
ZONE
DAMPER
B
F
CONDENSING
UNIT
OR
HEAT PUMP
OUTDOOR
UNIT
A
*ZONE 4
THERMOSTAT
(ZONE)
ZONE
DAMPER
OUTDOOR
THERMOSTAT /
BALANCE
POINT SENSOR