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Heat Pump Mode Operation Sequence of Operation
1. The thermostat sends a 24VAC signal on Y to the unit
requesting heating.
2. Contactor energizes starting compressor and outdoor
fan
3. Request sent to indoor blower motor for heating
speed. Blower starts after 6 second blower on delay
4. The unit is now operating the heat pump in the heating
mode
5. Once the thermostat satisfies, the Y terminal opens
ending the call for heating.
6. Compressor & Outdoor Fan de-energize
7. Indoor blower motor shuts off after the 60 second
programmed fan off delay.
Heat Pump to Gas Heat Sequence of Operation
Note: If the heat pump cannot satisfy the load, the
sequence of operation changes and the unit will switch
from the heat pump to gas heating.
1. The thermostat sends a 24VAC signal on Y to the unit
requesting heating.
2. Contactor is energized starting the compressor and
outdoor fan.
3. Request sent to indoor blower motor for heating
speed. Blower starts after 6 second blower on delay.
4. The unit is now operating the heat pump in the heating
mode.
5. If the thermostat cannot be satisfied, or the outdoor
thermostat changes to gas heating operations, W1 is
energized, and Y is de-energized.
6. The compressor and outdoor fan are turned off.
7. Gas heating cycle begins.
Outdoor Thermostat
For optimal performance, a dual fuel thermostat with
an outdoor temperature sensor should be used.
TSTATGTS3275 (Emerson Dual Fuel thermostat)
with TSTATTSORS (outdoor temperature sensor) is
recommended.
This will allow the installer to control when the unit
switches from heat pump to gas heat based on a set point
entered into the thermostat. It is recommended to set the
thermostat between 35° - 45°F, depending on regional
climate and energy rates.
Optional Outdoor Thermostat (OTDFPKG-01)
The outdoor thermostat is an optional accessory that
can be set from 0 - 45°F and is set inside a "birdhouse"
enclosure. This enclosure will be mounted near the blower
access panel. The dimples and knock-out are located
on the corner posts, providing ease of installation. Once
the thermostat closes, a 24 volt signal is sent to the W1
terminal instead of the Y terminal and the heating cycle will
change from Heat Pump to Gas heating. It is recommended
to set the thermostat between 35-45°F depending on
regional climate and energy rates.
NORMAL SEQUENCES OF OPERATION
Heating Cycle (Natural Gas/ LP)
1. The Dual Fuel unit will operate in gas heat mode
when the thermostat calls for a W-1 or W-2 signal. If
outdoor thermostat is installed, the unit will operate in
gas heat when ambient is below set point or the unit
receives call for low or high stage gas heat.
2. Induced draft blower energizes for 15-second pre-
purge.
3. A 7-second trial for ignition begins by energizing the
low and high stages of the gas valve along with this
spark ignition.
NOTE: The igniter produces a very intense electrical
spark that ignites the gas.
4. Main burners light and control detects presence of
flame.
5. If the call is for low stage heat, the induced draft
blower switches from high to low speed and the gas
valve from high to low stage within 5 seconds after
the main burners light. If call is for high stage heat,
induced draft blower remains at high speed and high
stage gas valve remains open.
NOTE: If a W2 is not used, the control will step to
low stage after the main burners light and remain at
low stage for 5 or 10 minutes, depending on jumper
position. If the jumper is set to none, you will never
get a call for high stage heat. If the call for HEAT
remains after the transition delay time expires, the
control will transition from low stage to high stage.
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