Lennox Harmony III Installation Instructions Manual page 12

Cooling Staging Temperature Jumper
The Cooling Staging Temperature jumper bank is used to
set the discharge air temperature at which the unit will turn
on second stage. It is selectable between 50°, 55° and
60°F. There is a 7 degree total differential associated with
this staging temperature. The differential starts at the set-
point, and extends to 7 degrees above the setpoint.
For example, with the setting at 50°F, and the unit running
in first stage with a discharge temperature of 55 degrees,
the unit will continue to run at first stage. Should the dis-
charge temperature rise due to increased zones calling,
the temperature would have to reach 57°F before the unit
would start running at second stage.
Cooling Maximum and Minimum Settings
Jumper Setting = 50°F
Settings can be from 50°F to
60°F with 7°F differential
57°F
total
differential =
either speed
7°F
50°F
45°F
Figure 16
Transformer rating should be sized to
adequately handle zone dampers
(1−4) plus relays (K1−K4) not to
exceed class II wiring limit of 75 VA.
Combined load of zone dampers and
zone relays not to exceed 60VA.
Use Lennox Part 69J56 for Zone
Relays 1 through 4.
505023M 04/06
Jumper Setting = 60°F
high speed
67°F
total
differential =
7ºF
60°F
low speed
45°F
blower only
Damper and Extended Damper Wiring Diagram
(NOT TO EXCEED
75 VA) CLASS II
WIRING
EXTENDED
ZONE 1
DAMPER
EXTENDED
ZONE 2
DAMPER
EXTENDED
ZONE 3
DAMPER
EXTENDED
ZONE 4
DAMPER
The discharge air would then have to reach below 50°F be-
fore the unit would stage down to first stage again. This will
prevent any rapid staging of the equipment. See figure 16.
Common System Component Wiring
Use thermostat wire to connect dampers, damper trans-
formers, and the DAS probe with the zone control system.
Avoid running any control wiring close to AC house
wiring. If this cannot be avoided, limit close parallel
of power and control wiring to a few feet.
Dampers and Damper Transformer Wiring
Connect dampers to the zone control board as shown in
figure 17. A total of six dampers may be connected at the
damper output terminals on the zone control board. If addi-
tional dampers are used, additional transformers and re-
lays will be needed.
Fuse F1 will protect the damper outputs from a short circuit
or overload in the damper wiring.
If dampers are applied to the return duct system, the
dampers for each zone must be wired in parallel. Connect
damper transformer to zone control board terminal block.
Refer to the Extended Damper Wiring section in figure 17
for wiring connections.
Discharge Air Sensor (DAS) Probe Wiring
Wire discharge air sensor probe to zone control board. The
variable immersion-temperature probe is not polarity sen-
sitive.
EXTENDED
DAMPER
120 VAC
WIRING
EXTENDED
DAMPER
TRANSFORMER
24 VAC
ZONE
RELAY 1
ZONE
RELAY 2
ZONE
RELAY 3
ZONE
RELAY 4
Figure 17
Page 12
IMPORTANT
ZONE 1
DAMPER
ZONE 2
DAMPER
ZONE 3
DAMPER
ZONE 4
DAMPER
ZONE CONTROL,
THERMOSTATS,
& DAMPERS
TRANSFORMER
24 120
VAC VAC