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Table 8. Heat Pump Parameters
Parameter
Description
Defrost Termination
Temp
(Single and Two-Stage
Lennox Communicating
Heat Pump Units)
This is the temperature that defrost mode will be terminated. In dual fuel applications (furnace and heat pump), defrost tempering is automatically enabled and operates
as follows:
• Furnace will run for 75 seconds ON then after 90 seconds OFF for two cycles.
•
After the first two cycles, the furnace will run for 60 seconds ON then cycle OFF for 90 seconds.
• This cycle will be repeated unit the room thermostat is informed by the outdoor control that defrost has terminated.
The range is 50 - 100°F (10.0 to 37.78°C). Default is 50°F (10.0°C) and with an incremental adjustment of 10°F (5.56°C).
Variable capacity - Both Furnace and Heat Pump are Modulating:
When the thermostat receives information that the heat pump has entered defrost the thermostat sends a minimum rate heating demand to the furnace. Then the
thermostat terminates the minimum rate heating demand upon defrost completion or any time the heat pump stops. (i.e., pressure switch opens, mode switch changes,
etc.)
Staged – Both Furnace and Heat Pump are Multi-Stage:
When the thermostat receives information that the heat pump has entered defrost the thermostat performs the following :
•
Sends a first stage heating demand to the furnace.
•
After 75 seconds elapse from the time the first stage demand was sent, the thermostat terminates the furnace heating demand.
•
After the furnace minimum off time has elapsed (90 seconds) from the time the previous heating termination, the thermostat starts first stage furnace heat again by
sending the first stage heating demand. This is the new adjustable gas heat delay setting for zoning.
•
After 60 seconds elapse from the previous heating demand being sent, the thermostat terminates the furnace heating demand.
•
Repeat steps 3 and 4 while defrost is active, terminating any running furnace heat demand when the HP indicates that defrost is no longer active or any time the heat
pump stops. (i.e., pressure switch opens, mode switch changes, etc.)
NOTE:
The on times above assume the minimum furnace ignition time of 35 seconds.
Dehum Airflow
Adjustment Adder
(Lennox Variable
Capacity Heat
Pumps Only)
Dehumidification airflow = HUMID Mode CFM table value for a given thermostat dehumidification adjustment adder (High Normal Cooling Airflow CFM x
Dehumidification Airflow Adjustment Adder in percentage.
Both these values are in the installer set up under dealer control center > equipment > heat pump. Range is 0 to 30%. Default is 28%.
NOTE:
Deactivated in auxiliary dehumidification and enhanced dehumidification accessory (Humiditrol)
Equipment Name
A unique name can be assigned to this component. Name can be up to 29 characters. Name can consist of letters, numbers, special characters and spaces.
High Normal
Cooling Airflow
(Lennox Variable
Capacity Heat
Pumps Only)
Thermostat values shown are defaults. This value can be adjusted up or down to meet each application requirements.
The range is 450 - 2150 CFM. Default is dependent on unit capacity with an incremental adjustment of 25 CFM.
Fan Cycling
(Single and Two-Stage
Lennox Communicating
Heat Pumps)
Options are ON or OFF. Default OFF.
High Normal HP
Heating Airflow
(Lennox Variable
Capacity Heat
Pumps Only)
Thermostat values shown are defaults. This value can be adjusted up or down to meet each application requirements.
The range is 450 - 2150 CFM. Default is dependent on unit capacity with an incremental adjustment of 25 CFM.
Low Normal
Cooling Airflow
(Lennox Variable
capacity Heat
Pumps Only)
Thermostat values shown are defaults. This value can be adjusted up or down to meet each application requirements.
The range is 450 - 2150 CFM. Default is dependent on unit capacity with an incremental adjustment of 25 CFM.
