OPERATION MODES
21
OPERATION - DEFROST MODE
This mode of operation is used to remove accumulated frost from the outdoor coil, improving the airflow across the outdoor coil,
which results in increased efficiency of the Acadia Heat Pump. If one of the Defrost Initiation Methods determines that Defrost
Mode is needed, the Controller enters Defrost Mode. A Defrost Mode is separated into three parts: Mode 1 Initialization (d1),
Mode 2 Actual Defrost (d2), and Mode 3 Termination (d3). During Defrost Mode, if the thermostat call is lost or changes and/or
the ambient temperature changes, the Controller shall ignore those changes and continue the normal Defrost Mode of operation.
DEFROST MODE ALLOWANCES AND LIMITATIONS
1. Defrost Mode, under any condition, will ONLY be allowed if:
The outdoor ambient temperature is above -30°F, or below 45°F (above -34.4°C, or below 7.2°C) and
The system is in Heat Mode 2/3/4/5; the Primary Compressor running with 2 cylinders.
2. The Accumulated Runtime shall pause when the ambient temperature reaches the Defrost-Allowed Limit Temperature, 45°F
(7.2°C), and above. If the ambient temperature stays above the Defrost-Allowed Limit Temperature for 45 minutes or more, the
Accumulated Runtime will reset.
3. Once defrost begins, if the ambient temperature goes above 45
o
F (7.2°C), defrost will run to completion.
4. There is ALWAYS 45 minutes minimum time between defrost cycles, even if the Demand Defrost is calling.
DEFROST INITIATION METHODS
The following are the methods that initiate Defrost Mode:
Sacrificial Defrost Initiation
Sacrificial Initiation occurs every 45 minutes of Primary Compressor, running with 2 cylinders, accumulated runtime. This type
of defrost initiation will occur after a power up of the Controller and after a time terminated defrost cycle. After the Primary
Compressor, running with 2 cylinders, runs for an accumulated total time of 45 minutes, the Controller will enter a defrost. If
the Controller terminates the defrost cycle because the maximum allowed defrost time has expired, then the Controller will
continue sacrificial initiations until the coil reaches the specified temperature threshold. When the coil temperature reaches
the specified temperature while in a defrost cycle, the Controller will switch to the demand defrost initiation method for
starting a defrost cycle.
Manual/Time-Temperature Defrost Initiation
Manual Defrost is initiated immediately when the MANUAL/TIME-TEMP DEFROST button is pressed for 1 second as long as the
defrost conditions are met. If the MANUAL/TIME-TEMP DEFROST button is pressed for 5 seconds, the controller will switch to
an initiation method that causes a defrost cycle whenever the Primary Compressor, running with 2 cylinders, has run for an
accumulated total time of 45 minutes. Time-Temperature defrost initiation does not care how the defrost cycle terminates. It
will continue the 45 minutes initiation until the C-TEMP DEFROST button is
pressed for 5 seconds. When the Controller leaves the Time-Temperature initiation method because of a 5 second button
press, the Controller will revert to the initiation method determined by the last defrost cycle termination method. No action
happens if the MANUAL/TIME-TEMP DEFROST button is pressed during a defrost cycle.
Demand Defrost Initiation
Demand defrost initiation is determined by an equation which utilizes a maximum temperature separation between the Coil
and Ambient temperatures.
Accumulated Runtime Defrost Initiation
During Heat Modes 2/3/4/5, the Controller tracks the Accumulated Runtime and will initiate a defrost cycle if the time limit
expires before the maximum temperature separation occurs between the Coil and Ambient temperatures (Demand). Any time
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