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Sequence of Operation
When power is first applied, the green system power
led will remain off for approximately 6 seconds. After
6 seconds, this LED will begin to flash indicating that
the board is working normally. Note that immediately
after the board is powered, there is a four minute
minimum off delay during which only the fan output
will respond.
When operating in the Heat mode, the heating
equipment will not stop operating until all heat calls
have been satisfied. Any existing cooling calls will then
be satisfied. Equipment operation is only interrupted if
an Emergency Heat call (heat pump applications only)
exists or if an opposing mode call from another zone
exists for 20 minutes. Similarly, cooling calls will be
satisfied until all calls for cooling end or an opposing
call from another zone exists for 20 minutes. The
sequence of operation is dependent on the position of
the ZONE 1 or ANY ZONE switch and the HEAT PUMP
or HEAT/COOL switch. 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.
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
Heating/Cooling LED on the control panel will flash
during a high/low limit temperature interrupt. Once the
temperature drops/rises 10°F, the equipment is turned
back on if the call for conditioning still exists, and the
Heating/Cooling LED will stop flashing.
DAMPER OPERATION
The “NO” output will be energized and the “NC” output
will be de-energized for any zone not calling for heating
or cooling while the equipment output is energized and
during the damper purge time delay. During equipment
operation or during the damper purge time delay,
should all zones stop calling for heating or cooling, the
damper terminals will remain in the position they were
in before all zones stopped calling.
Damper Purge Time Dela
y
When the PURGE/NO PURGE Selector is set to NO
PURGE, the damper purge time delay is 3.5 minutes
and begins when the equipment output(s) turn off.
NO PURGE is the preferred method of purge control
for Lennox furnaces and air conditioners. When the
PURGE/NO PURGE Selector is set to PURGE, the
damper purge time delay is one (1) minute.
CONTINUOUS FAN OPERATION
A call for Fan from any zone will initiate the G
equipment output terminal. The normally open (NO)
damper terminal at all zones not calling for continuous
fan will be energized.
HEATING AND COOLING EQUIPMENT OPERATION
COOLING OPERATION
When a zone makes a call for Cooling, the Y1, G and O
terminals will energize. The Y1 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 Y1 terminal is de-energized,
a minimum off time delay of 4 minutes must elapse before
it can be energized again. Should any call for Cooling not
be satisfied in the time that is set on the STAGE dip switch
bank, or should the “2S” terminal of any calling zone be
energized, or should the number of zones calling for
conditioning be greater or equal to the # Zones to Stage
setting, the Y2 terminal will energize. For greater detail on
how the system configuration DIP switch positions affect
staging, see the system setup flowchart starting on page
20. When none of the conditions that initiated the Y2
terminal are present, the Y2 terminal will de-energize.
Once de-energized, the Y2 terminal can not be energized
again until a 4-minute minimum off time delay elapses. The
O terminal remains energized until there is a Heat call.
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 Y1 (and Y2) terminal is de-energized.
If the jumper is in the NO PURGE position, the
G terminal will de-energize immediately.
IMPORTANT: Should a short or open circuit be
detected across the Discharge Air Sensor (DAS)
terminals, the zone system will respond only to
Zone 1 and the dampers will not energize.
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