Page 4
505023M 04/06
Balance Point Sensor (Outdoor Thermostat)
A balance point sensor (56A83, shown in figure 3) may be
implemented in a dual-fuel (Option 3) system. This ther-
mostat monitors the outdoor temperature, compares it to
the balance point setting, and signals the zone control if the
reading is below the set point. The zone control then
instructs the gas furnace to provide all the heating and pro-
hibits the heat pump from attempting to fill a demand for
heat.
Figure 3
Balance Point Sensor
Install Heating and Cooling Equipment
The total HVAC system must be properly proportioned to
provide the best comfort. Follow all equipment installation
instructions provided with each unit.
IMPORTANT
LENNOX recommends ONLY Harmony II
®
and
Harmony III
t
Zone Control Systems for use with
Variable Speed Blower Motor (VSM) technology.
Option 1 − Lennox Gas Furnace with Variable
Speed Blower Motor (VSM)
& Lennox Condensing Unit
1. Lennox Gas Furnace with VSMThe VSM allows the
zone control system to distribute the amount of air that
goes to each zone. These are the only furnaces avail-
able that work with the Harmony III
t
zone control sys-
tem.
2. Lennox Condensing UnitUse condensing units as
shown in table 2.
Table 2
Condensing Units / Heat Pump Units
No. of
zones
Comparative
Zone sizes
Lennox Condensing
Unit or Heat Pump
2
Equal
Single or Two−stage
2
Unequal
Two-stage only
3 or 4
Equal or Unequal
Two-stage only
Option 2 − Lennox Blower Coil Unit with VSM
& Lennox Heat Pump
IMPORTANT
LENNOX recommends ONLY Harmony II
®
and
Harmony III
t
Zone Control Systems for use with
Variable Speed Blower Motor (VSM) technology.
1. Lennox Blower Coil Unit with VSMUse ONLY blower
coil units equipped with a variable speed blower motor;
other type of units will not allow the Harmony III
t
zone
control system to proportion the amount of air going to
each zone.
2. Lennox Heat Pump Unit
Use Heat Pumps as shown
in table 2.
Option 3 − Lennox Gas Furnace with VSM
& Lennox Heat Pump
1. Lennox Gas Furnace with VSM[As described in Op-
2. Lennox Heat Pump Unit
Zone Control Components Installation
Zone Control Board
Select an installation site for the Harmony III
t
board con-
sidering the following location parameters:
S
Is conveniently accessible and centrally located to fa-
cilitate wiring from thermostats, dampers, pressure
switch (if used), and HVAC equipment.
S
Is in a non−condensing area (such as a closet).
S
Is NOT in a laundry room (nor other room in the house
where the humidity would typically be much higher
than the rest of the house).
S
Is NOT in any part of the building where the tempera-
ture may exceed 150
_
F.
IMPORTANT
The electrical power source for the zone control sys-
tem, i.e. the transformer primary, and furnace or
blower coil unit must be the same source. In addi-
tion, the zone control system power−up must occur
at the same time or before the furnace or blower coil
unit is powered up.
Discharge Air Temperature Probe
CAUTION
This device is manufactured using unpainted and
prepainted metal. Sharp sheet metal edges can
cause injury. When installing the device, avoid acci-
dental contact with sharp edges.