Lennox Harmony II Zone Control System Installation Instructions Manual page 28

Auto Changeover Mode
When Auto mode is selected at the control panel, the
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zone control system can respond to both heating and
cooling demands from zone thermostat(s). For exam-
ple, this will allow the system to heat the space in the
morning and cool in the afternoon.
It is possible for heat and cool demands to be present
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at the same time from different zones (called opposing
demands). For example, one zone may call for cooling
while another calls for heating.
Opposing demands are satisfied on a first come first
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served basis. If a heating demand and a cooling de-
mand reach the control center at the same time, the
heating demand is satisfied first.
If opposing demands persist, the system will work to
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satisfy the current demand for a maximum of 20 min-
utes, then switch over and try to satisfy the opposing
demand for a maximum of 20 minutes. When one or
the other demands is satisfied, the system will work to
satisfy the remaining demand.
NOTE − It is possible, but not desirable to allow opposing de-
mands to persist because this may consume excess ener-
gy. If this happens, pay special attention to the installation
(i.e. zone arrangement, supply registers, return registers,
zone loads etc.) and make adjustments as necessary.
Table 4 shows the time delays which may be expected
when opposing demands are received from the zone ther-
mostats. The control center will acknowledge a new or op-
posing demand as soon as it is received by momentarily
flashing DIAG 2 on then off. If the first demand is not satis-
fied by the time the delays are elapsed, the system will
switch over and begin satisfying the opposing demand.
During the switch over, a switch over delay may be im-
posed before the system begins satisfying the new de-
mand. The system will not switch over until an opposing
demand has been present for at least 5 minutes.
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C−Harmony II Control Panel
Zone / Central / System Off Modes
Central Mode
When in Central mode, the system responds only to the
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master thermostat and all rooms receive conditioned air.
When in Central mode, control panel should be set for
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Auto changeover so that heat/cool selection can be
made at the master thermostat.
When the system is in Central mode, the system responds
to heating or cooling demands only from the master ther-
mostat. All dampers remain open and the blower operates
at full speed (minus the amount selected by the heating air
reduction jumper).
While the zone control system is in Central control and in
Fan-Auto mode, the blower in the indoor unit cycles on and
off with demand, and delivers air to all zones. In Fan-On
mode, the furnace blower will run continuously at a re-
duced rate (dictated by the jumper) and supply air to all
zones after a heating or cooling demand is satisfied.
Zone Mode
The Zone control mode uses the zone control system to its
fullest potential. While in this mode the zone control system
will respond to demands from any zone. It will control the
dampers and regulate the blower speed to maintain comfort.
Select Heating, Cooling, or Auto changeover at the control
panel.
When the system is in Zone mode, the zone control system
responds to demands from any zone thermostat. The only
dampers that remain open are those supplying air to the de-
manding zone(s); and all other dampers will close. The
blower operates at a speed based on the position of the
CFM selection jumpers (and the heating air reduction jump-
er if heating is being called for).
The control center knows how many zones are connected
by determining how many thermostats are connected. If a
thermostat is disconnected, then the zone is disconnected.
Setting a zone air jumper to OFF does not disconnect a
zone.
NOTE − While the feature of Fan-On has been included in
the Zone Control mode, it is not recommended. To ensure
that the zone control performs optimally, avoid mixing air
between the zones.
System Off Mode
When the zone control system is in the System Off mode,
the compressor and all heating equipment are turned off.
D−Fan Auto / Fan On Modes
Fan Auto Mode
In Fan−Auto mode, the blower will cycle on and off with
each demand, and deliver air to calling zones. During gas
or electric strip heating, the blower may continue after the
end of a demand until the heater is cooled sufficiently.
Fan On Mode
When the Harmony is in Fan−On mode and all the de-
mands have been satisfied, all dampers open and air circu-
lates to all zones. When a cooling or heating demand is
present, the system responds by closing all dampers ex-
cept for the demanding zone.
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