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A Time Delay Override (TDO) button is available on the
control panel to speed up the internal timer by a factor
of 60 for system checkout. One second of holding down
the button relates to one minute of speed up time in the
control.
HEATING AND COOLING EQUIPMENT OPERATION
Heating Operation
When a zone makes a call for Heat, the W output
terminal will energize. The G terminal will also energize
if the ELECTRIC/GAS jumper is in the ELECT position.
The W terminal de-energizes when (1) all zones stop
calling for Heat, (2) the call has exceeded the heat/cool
changeover time limit while a cooling call exists or (3)
the call is interrupted by the high limit setting. When the
W terminal is de-energized, a minimum off time delay of
4 minutes must elapse before it can be energized again.
Fan Purge
Time Delay
If the ELECTRIC/GAS jumper is in the ELECT
position and the PURGE/NO PURGE jumper is in the
PURGE position, the G terminal will remain energized
for one minute after the W terminal is de-energized.
The NO PURGE setting is the preferred purge control
setting for Lennox equipment. Lennox equipment
includes controls which sequence the indoor fan off
after a call for heat has been satisfied.
If the ELECTRIC/GAS jumper is set in the GAS
position, the G terminal does not turn on during purge
regardless of the position of the PURGE or NO
PURGE switch. Lennox furnaces will control the
purge though the furnace control board cool down
feature. The cool down time is often adjustable at the
furnace control board up to 3.5 minutes. NO PURGE
is the preferred method of purge when this zone
panel is applied to Lennox equipment.
Cooling Operation
When a zone makes a call for Cooling, the Y and G
terminals will energize. The Y terminal de-energizes
when (1) all zones stop calling for Cooling, (2) the call
has exceeded the heat/cool changeover time limit while
a heat call exists or (3) the call is interrupted by the low
limit temperature setting. When the Y terminal is de-
energized, a minimum off time delay of 4 minutes must
elapse before it can be energized again.
Fan Purge Time Delay
If the PURGE/NO PURGE jumper is in the PURGE
position, the G terminal will remain energized for one
minute after the Y terminal is de-energized. If the
jumper is in the NO PURGE position, the G terminal
will de-energize immediately.
Heat/Cool Changeover: When a call for heating or
cooling exists and an opposing call is made from
another zone, a 20 minute timer is activated. If the
original call is not satisfied within that 20-minute time
period, the call will be interrupted, turning the equipment
off and allowing for the normal fan purge cycle and
minimum equipment off time. The opposing call will then
be answered. After 20 minutes, if the original call still
exists, the opposing call will be interrupted and the
original call can once again be recognized.
High/Low Limit Temperature: The high/low limit
temperature settings are designed to prevent the heat
exchanger from overheating or the cooling coil from
freezing. The temperature sensor in the supply duct
senses the discharge air temperature and interrupts the
heating/cooling equipment (depending on the Heat and
Cool temperatures set on the control panel) before
overheating/freezing occurs. When a heating/cooling
call is interrupted by the high/low temperature limit, the
zone control panel turns the equipment off and
energizes the G terminal (if not already energized). The
W or Y LED on the control panel will flash during a
high/low limit temperature interrupt. Once the
temperature drops/rises 10°F and the minimum off time
has expired, the equipment is turned back on if the call
for conditioning still exists. The Heating/Cooling LED will
stop flashing.
IMPORTANT: Should a short or open circuit be
detected across the DAS terminals, the zone system
will respond only to Zone 1 and the dampers will
not energize.
Sequence of Operation