9
Configuring the
Fallback Algorithm
The DKN+ Fallback logic enables the control of indoor
unit by a thermostat using G, Y and W contacts. The DKN+
Fallback logic is available as a default until the adaptor is
connected to the cloud. Once the adaptor is connected to
the cloud the Fallback logic is disabled automatically.
Residual Operation:
Most Thermostats have a residual
operation period that keeps fan (G) energized for a few
seconds to few minutes to dissipate heat/cool from the
unit. During this time, the unit is commanded to a high
setpoint (cooling) or a low setpoint (heating) for a period
of time and the fan remains operational. Once residual
fan operation is stopped the unit turns Off. The residual
operation time is 70 seconds by default and adjustable by
the DKN App for the DKN+ adaptor. The setting should be
at least 10 seconds higher than value set at the thermostat.
Fan Speed
: During the fallback logic, the indoor unit will
use its last fan speed set at the indoor unit. At the time of
install make sure to set the desired fan speed in cooling
and heating from the DKN+ or using the VRV Remote
controller.
Requirements for Fallback logic.
1) The thermostat is hardwired to the DKN+ adaptor.
2) The DKN+ adaptor is not connected to the cloud.
3) The DKN+ adaptor is the P1P2 Main Remote
Controller.
4) A return air temperature (R1T) sensor must be
available at the indoor unit or remote temperature sensor
5) Set the field setting to enable fan operation in thermo-
Off condition to the user set value at the indoor unit.
6) Set the field setting to allow indoor unit to operation
with deadband of 0.9°F or 0.5°C.
Thermostat
Command
Indoor unit
Mode
Indoor unit
On/Off
Indoor unit Setpoint
G
Fan
On
N/A
Y
Cool
On
Calculated by the fallback logic.
Larger Alpha = Large Setpoint
corrections, smaller Alpha = smaller
alpha corrections.
W
Heat
On
Calculated by the fallback logic.
Larger Beta = Large Setpoint
corrections, smaller Beta = smaller
setpoint corrections.
G,Y,W open
Last Mode
Off
N/A
The Fallback logic works by dynamically adjusting
indoor unit’s internal setpoint with reference to the room
temperature based operation signal from the thermostat.
When the adaptor is first connected to the indoor unit, the
minimum cooling setpoint or maximum heating setpoint is
used as initial setpoint. As the adaptor continues to receive
the signal from thermostat, the new setpoint is calculated
to maintain thermo-on status. The
Alpha
(cooling) and
Beta
(heating) numbers affect the calculation of new
setpoint. Higher alpha or beta values cause the setpoint
correction to increase or decrease by a larger amount. The
alpha and beta value are fixed during commissioning by
the installer.
Alpha
Beta
3ºF - 1.66ºC
3ºF - 1.66ºC
5ªF - 22.78ºC
5ªF - 22.78ºC
7ºF - 3.89ºC
7ºF - 3.89ºC
