GENERAL
Page 4
505023M 08/11
System Components
The Harmony IIIt zone control system consists of the fol-
lowing (n − required):
n Harmony Harmony IIIt zone control panel (included)
n Discharge Air sensor (included)
n Thermostats (1 for each zone; ordered separately)
n 24VAC Power Transformer(s) (ordered separately)
n Dampers (ordered separately)
n Pressure Switch and Tee w/Schrader valve (for Heat Pump
systems; ordered separately)
S Balance Point Sensor (Optional for Dual Fuel systems)
S Defrost Tempering Kit (Optional for Dual Fuel systems)
S Remote Vacation Switch (optional; ordered separately)
Zone Control System
The Harmony IIIt zone control system monitors electrical
signals and directs control signals between thermostats,
dampers, and HVAC equipment (see figure 1).
JUMPERS:
STAGING
TEMP‘
HEATING−−
COOLING−−
AIR
REDUCTION
CONT.−−
HEATING−−
EQUIPMENT
CONNECTIONS
THERMOSTAT
CONNECTIONS
24VAC
CONNECTIONS
PIAB
JUMPERS
SYS CONFIG &
E−HEAT JUMPERS
DIAGNOSTIC
LEDS
TIME
DELAY
OVER-
RIDE
FAULT
RECALL
OUTDOOR THERMOSTAT /
BALANCE POINT SENSOR
CONNECTIONS
PRESSURE
SWITCH CON-
NECTIONS
DISCHARGE
AIR SENSOR
CONNECTIONS
DAMPER
CONNEC-
TIONS
FUSES
SYSTEM OPERATION LEDS
REMOTE
VACATION
SWITCH;
CONNECTIONS
FOR HZA
Figure 1. Harmony IIIt Zone Control Panel
Discharge Air Sensor (DAS)
A discharge air temperature sensor (88K38) monitors the
supply air. This electronic sensor’s probe is inserted into
the discharge air plenum to gather air temperature data for
the zone control panel. Figure 2 shows the kit; see figure 3
(Page 6) for location of the sensor.
TEMPERATURE/RESISTANCE CHART
TEMP ºF RESISTANCE (OHMS)
30 34,566
40 26,106
50 19,904
60 15,313
70 11.884
80 9,298
90 7,332
100 5,826
Figure 2. Discharge Air Sensor
Thermostats
IMPORTANT
Use only Electronic thermostats. Mechanical or
electro-mechanical thermostats will not work with
the Harmony IIIt zone control system.
For all zones, use thermostats that are of this type:
S electronic thermostat
S single-stage
S non-heat pump
S non-power robbing
S autochangeover or non−autochangeover
S Lennox recommends that zone 1 thermostat (central [vaca-
tion] mode controller) be programmable.
S Each thermostat must have a deadband between HEAT and
COOL.
Recommended thermostats include:
S ComfortSenset 7000 model L7742U Touch Screen Ther-
mostat. (IMPORTANT! When using this thermostat, only
Precision Mode dehumidification can be used wherein 2°F
of over-cooling is allowed. Also, it cannot reduce the blower
speed because the zone control DS signal controls the blow-
er. Thermostat D terminal is not used.
S ComfortSenset 5000 model L5711U Touch Screen Ther-
mostat − 1 heat / 1 cool / 7−day programmable.
Transformer
The dampers, zone control panel, zone thermostats and
Humiditrol
®
Zoning Accessory (if EDA is used) are pow-
ered by a single, field−provided 24VAC transformer. To-
gether, the zone control panel and thermostats require
10VA; dampers require 10VA each. The transformer must
have an adequate VA rating to serve all components (see
recommendations in table 1).
IMPORTANT
Up to 5 dampers per zone may be connected in par-
allel to the zone control panel not to exceed a total
of six dampers for entire system.
Also, if more than 6 dampers are used, another
transformer and isolation relay will be necessary.
Table 1. 24VAC Transformer selection chart
Catalog
Number
Size Description
VA LOAD =
Panel plus−
10P17 40VA 120/208/240VAC, 24VAC 3 dampers
10P87 50VA 120/208/240VAC, 24VAC 4 dampers
12P61 75VA 120/208/240VAC, 24VAC 6 dampers
83P74 _ Electrical Box (4-in. square)
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