GENERAL
Page 2
505023M 08/11
GENERAL
Shipping & Packing List
Items shipped with the Harmony IIIt Zone Control System
include:
1 − Harmony IIIt Zone Control System unit
1 − Discharge Air Sensor
Additional itemsordered separately; include (see Sys-
tem Components on Page 4):
S Transformer
S Dampers
S Thermostats
S Balance Point Sensor kit (56A87)
S Pressureswitch (For Heat Pump Option):
HFC−22 (27W12); HFC−410A (27W13)
S Tee for vapor line High Pressure Switch (87071)
S Defrost Tempering Kit (67M41)
S Humiditrol
®
Enhanced Dehumidification Accessory (EDA),
EDA−024B (94M41), EDA−036C (94M42), EDA−060D
(94M43)
S Humiditrol
®
Zoning Accessory (HZA) Kit (39W67) (required
if Humiditrol
®
EDA, above, is used)
Introduction
The Lennox Harmony IIIt Zone Control System manages
the distribution of conditioned air to specific areas or zones
in a house or small commercial building by directing heated
or cooled air to occupied areas without conditioning un-
used areas. This improves economy while providing a bal-
anced and comfortable environment. The system can be
used in the following Lennox HVAC system applications:
Option 1.Variable speed gas furnace used with a 2-stage
condensing unit.*
Option 2.Variable speed air handler unit (with or without
electric heat) used with a 2-stage condensing
unit or heat pump.*
Option 3.Variable speed gas furnace used with a 2-stage
heat pump.*
*A 1 stage condensing unit (heat pump) may be used under specific
circumstances as listed in Table 3 (see Page 5).
Variations on the options described above and included in
this document are: cooling−only, hot water coil, and cooling
system with electric heat applications.
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 control distribution of conditioned air to differ-
ent zones. This control allows conditioning of different
zones within a residence while using a single HVAC sys-
tem.
The zone control system operates in two modes: central
control (vacation mode) or zone control. LEDs on the
zone control panel indicate the current operating mode.
When the system is in the central control mode, a de-
mand from the central control thermostat results in condi-
tioned air being directed to all of the zones. In this mode,
zone 1 thermostat is designated as the controlling thermo-
stat; other thermostats are not used.
When the system is in the zone control mode, a zone is
conditioned only upon demand from that zone’s thermo-
stat.
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.
Optional Dehumidification Accessories
The Harmony IIIt zone control system may be used in con-
junction with a Humiditrol
®
Enhanced Dehumidification Ac-
cessory (EDA) and which also requires a Humiditrol
®
Zon-
ing Accessory (HZA). This document reflects the control
which is outfitted for connection to, and control of, the EDA
in a zone control system using the HZA. See Humiditrol
®
Zoning Accessory Installation Instructions for more infor-
mation.
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