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HEATING MODE
Heat Pump
1. The thermostat calls for heat. There is a six minute off-time
between cooling or heating cycles. If the system has cycled
off it will be a minimum of six minutes before it will be
allowed to restart.
2. The reversing valve toggles to relieve pressure differential
and then deenergizes.
3. The unit control will self-test, then perform a system check
to determine if sensors are correctly opened / closed.
4. An engine start is attempted. If start is successful, the
engine comes up to 1500 rpm. If the start is unsuccessful,
another start will be attempted. The engine will attempt 5
starts before a fault requiring a shut-down occurs. A fault
will be posted and a six minute delay will occur until another
five attempt cycle can be made. After three sets of failed
start attempts (15 actual start attempts) the system will
shut down, post a fault and lock out.
5. After a successful start, the indoor unit blower will start at
minimum speed. It is possible for the indoor blower to
already be operating if the thermostat fan switch is set to
continuous fan.
6. After the engine speed reaches adequate operating
temperature, the system will respond to thermostat com-
mands and speed up or slow down as required. Maxi-
mum heating is achieved when the engine speed
reaches 3000 rpm.
Furnace
1. The thermostat calls for heating and the heat pump system
is disabled.
2. The inducer motor is energized. Correct combustion air
flow is proven by the pressure switch.
3, The hot surface igniter is energized for 17 seconds. The
gas valve then opens for seven seconds.
4. After the gas valve opens, the flame sensor must detect
flame within seven seconds. After flame is present for 30
seconds, the circulating blower is energized and allows
normal furnace operation until the call for heat is satisfied.
5. When the call for heat is satisfied, the thermostat circuit
opens and the gas valve closes. The inducer will continue
to run for 15 seconds
6. The furnace blower will operate for the time chosen on the
fan-off setting.
7. If flame is not detected, the control module will re-try
ignition after a 60 second wait.
8. After 60 seconds, the ignition sequence is restarted with
an additional 10 seconds of igniter warm-up time. If this
ignition attempt is unsuccessful, one more re-try is at-
tempted before lockout.
9. A momentary loss of gas supply, flame blow out or a
shorted or open condition in the flame sensor circuit will be
sensed within 0.08 second. The gas valve will deenergize
and the control will restart the ignition sequence after
waiting 60 seconds. Recycles will begin and the burner will
operate normally if the gas supply returns, or if the fault
condition is corrected prior to the last ignition attempt.
Otherwise the control will lockout.
10. The control will repeat the ignition sequence for a total of
four recycles if flame is lost within the first 10 seconds of
establishment.
11. If flame is established for more then ten seconds after
ignition the control will clear the ignition attempt (retry)
counter. If flame is lost after 10 seconds, it will restart the
ignition sequence. This can occur a maximum of four
times.
12. During burner operation, a momentary loss of power of 50
milliseconds or longer will drop out the main gas valve. When
the power is restored, the gas valve will remain deenergized
and a restart of the ignition sequence will begin immediately.
DEFROST TIME ADJUSTMENT
(ELECTRIC HEAT AND ADD-ON HOT WATER
HYDRONIC HEAT ONLY)
The unit has a unique ambient modified, time-temperature
defrost control that automatically adjusts to changes in outdoor
temperature.
FIGURE 16 - DEFROST INITIATION TIMES CHART - (ELECTRIC OR ADD-ON HYDRONIC HEAT ONLY)
515.35-N6Y
Unitary Products Group
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