SYSTEM OPERATION
11
temporary heat pump lockout and run the heat pump
again.
There are four adjustable items associated with Dual Fuel
control. In the same way as the System Target Time, each
of these items have defaulted values for Comfort Settings
1 – 5. Only when Comfort Setting 6 is selected will each
item be available for full adjustment.
1) Stage Up Percent (7 segment menu SUP): This
is a value that determines how far past the target
runtime the system should continue running the
heat pump before transitioning to the furnace. For
example, assume this menu was set to 20% with
a target runtime of 20 minutes. If the thermostat
did not remove the heating call after 20 minutes,
the system would allow for an additional 20%
heat pump run (20% of the 20 minute target is an
additional 4 minutes). In this case, the system
would transition to gas heat after 24 minutes if
the thermostat call was still present. Each time
this occurs, the system records this as a strike
against the heat pump (the strike is important
when looking at the Over Target Threshold)
2) Over Target Threshold (7 segment menu Ott): If
the heat pump has consecutively transitioned to
gas heat for the selected Over Target Threshold
amount of times, meaning for this many
consecutive cycles it has been unable to satisfy
the target time by itself, then the heat pump will
be temporarily locked out and the furnace will
become the primary heat source.
3) Stage Down Percent (7 segment menu SdP): This
only applies when the heat pump is in a temporary
lockout condition. In this case, the system will
be trying to determine when the best time is to
remove the lockout and run the heat pump again.
To determine the best time to remove the heat
pump lockout the system looks at how easily the
furnace is able to satisfy the thermostat using
Low Stage Gas Heat Only. Assume this setting
is 15% and the target time is 20 minutes. If Low
Stage Gas Heat can satisfy the thermostat in less
than 17 minutes (20 minutes - 15% = 17 minutes)
then the algorithm records a strike against the
gas furnace. (this strike is important when looking
at the Under Target Threshold).
4) Under Target Threshold (7 segment menu Utt):
If the furnace is able to satisfy the thermostat
using Low Stage Gas Heat Only for the selected
number of consecutive cycles the heat pump
lockout will be temporarily removed. The heat
pump will then be used
during the next cycle. If
the heat pump can satisfy the thermostat in less
than the System Target Runtime the temporary
heat pump hold will be completely removed and
the heat pump will become the primary heat
source again. if it fails to do so, the strike count
against the furnace will be reset and the furnace
will remain the temporary primary heat source
until the Under Target Threshold is reached again.
The system will automatically make adjustments in an attempt
to satisfy the thermostat as close to this target runtime as
possible. After a power cycle or mode change (cooling to
heating or heating to cooling) the system will run full capacity
for the selected mode during the first thermostat call. Based
on the selected target runtime and how long the initial cycle
takes to satisfy the thermostat, the control algorithm will adjust
the system stage times for a 2 stage unit or the capacity
demand percentage for an inverter / modulating unit for the
next cycle. Note: actual runtimes may change depending on
variations of load throughout the day.
The following table shows the default values for all
Comfort Setting Options (1 – 5)
Comfort
Setting
Option
Target
Time
(Minutes)
Stage Up
Percentage
(%)
Stage Down
Percentage
(%)
Over Target
Threshhold
(Strike Count)
Under Target
Threshhold
(Strike Count)
1
10
20
20
2
10
2
15
20
20
4
8
3
20
20
20
6
6
4
25
20
20
8
4
5
30
20
20
10
2
The following table shows the ranges for each of item
when the adjustable Comfort Setting Option 6 is selected.
The table shows the minimum value, the maximum value
and the defaulted value. All items can be adjusted up or
down by increments of 1 which provides full flexibility
for all items. Note: it is critical that these numbers be
set properly. If Comfort Setting option 3 is desired but
a target time of 60 is preferred, select Comfort Setting
Option 6 to enable all the adjustable menus, set the Target
Time to 60 and make sure the other menus are set to
match that of Comfort Setting Option 3.
Menu
Minimum Value Maximum Value Default Value
Target Time (t9t)
1 minute
240 minutes
60 minutes
Stage Up Percent (SUP)
0%
100%
20%
Stage Down Percent (SdP)
0%
100%
20%
Over Target Threshold (Ott)
1 strike
254 strikes
20 strikes
Under Target Threshold (Utt)
1 strike
254 strikes
20 strikes
Circulator Blower Speed
The Airflow quantity is displayed as a number on the three
7 segment displays, rounded to the nearest 100 CFM.
The display alternates airflow amount and the system
operating status.
Each furnace has a “Maximum CFM” it is capable of
providing. All fan operations (Constant CFM, Cooling
Airflow Profiles, Low and High Stage gas heat airflow,
outdoor Air Conditioner / Heat Pump Airflow, etc.) are
based off of multipliers which are percentages of this
maximum CFM. Max CFM is as follows:
