Lennox Harmony III Installation Instructions Manual page 3

System Components
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).
Harmony IIIt Zone Control Board
DAMPER
CONNEC
PRESSURE
TIONS
SWITCH CON-
NECTIONS
JUMPERS:
STAGING
TEMP'
HEATING−−
COOLING−−
AIR
REDUCTION
CONT.−−
HEATING−−
DISCHARGE
AIR SENSOR
SYS Config & E−HEAT JUMPERS
CONNECTIONS
time
delay FAULT
override RECALL
SYSTEM OPERATION LEDS
Figure 1
Discharge Air Sensor
A discharge air temperature sensor (88K38) monitors the
supply air. This electronic sensor's probe (see figure 2) is
inserted into the discharge air plenum to gather air temper-
ature data for the zone control board.
Discharge Air Sensor (Probe)
Figure 2
Separately-Ordered System Components
Thermostats
For all zones, use thermostats that are of this type:
S
electronic thermostat
THERMOSTAT
CONNECTIONS
BALANCE POINT
SENSOR
24VAC
CONNECTIONS
CONNECTIONS
FUSES
PIAB
JUMPERS
EQUIPMENT
DIAGNOSTIC
CONNECTIONS
LEDS
S
single-stage
S
non-heat pump
S
non-power robbing
S
autochangeover or non−autochangeover
Lennox recommends that zone 1 thermostat [central
(vacation) mode controller] be programmable. Each ther-
mostat must have a dead band between HEAT and COOL.
IMPORTANT
Use only Electronic thermostats. Mechanical or
electro-mechanical thermostats will not work with
the Harmony IIIt zone control system.
Recommended thermostats include:
t
S
SignatureStat
[IMPORTANT! When using this thermostat, only Pre-
cision 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 con-
trols the blower. Thermostat D terminal is not used.
S
®
Elite Touch Screen Thermostat − 1 heat / 1 cool /
7−day programmable (X4146).
Transformer
The dampers, zone control board, and zone thermostats
are powered by a single, field−provided 24VAC transform-
er. Together, the zone control panel and thermostats re-
quire 10VA; dampers require 10VA each. The transformer
must have an adequate VA rating to serve all components
(see recommendations in table 1).
24VAC Transformer Selection Chart
Catalog Size Description
No.
10P17 40VA 120/208/240VAC, 24VAC
10P87 50VA 120/208/240VAC, 24VAC
12P61 75VA 120/208/240VAC, 24VAC
83P74 _
Dampers
Motorized 24VAC powered closed/spring return open
dampers are standard for the Harmony IIIt zone control
system. However, power-open/spring-close" and power-
open/power-close" dampers can be accommodated.
Pressure Switch
A pressure switch [R−22 (21J18); R−410A (51M08)] is re-
quired for applications with a Lennox heat pump (Options 2
and 3). The pressure switch acts as a guard in case of high
head pressures during first− and second−stage heating.
Page 3
Thermostat − 1 heat / 1 cool (81M26)
Table 1
Electrical Box (4-in.
square)
HARMONY IIIT SERIES
VA LOAD =
Panel plus−
3 dampers
4 dampers
6 dampers