SAC = Su – ( Tu – T
AC
)
Where:
SAC - setpoint value currently applied to the indoor unit
Su - setpoint value written at Modbus side (register 4/5)
Tu - external temperature reference written at Modbus side (register 22/23)
TAC - ambient temperature that the indoor unit is using as the reference of its own
control loop (register 5/6)
When INMBSDAI001R000 detects a change in any of the values of
{ Su , Tu , TAC }, it will send the new setpoint (SAC) to the indoor unit.
o Once values have been entered in the “AC unit external temperature’s reference”
(register 22/23) and “AC unit temperature set point” (register 4/5),
INMBSDAI001R000 is going to estimate the temperature chosen implied (e.g. if a
“temperature setpoint (register 4/5)” of 22ºC, and an “external temperature
reference (register 22/23)” of 20ºC are entered, INMBSDAI001R000 will assume
that the user is demanding a +2ºC increase in temperature).
o By knowing at any time, the ambient temperature currently used by the indoor unit
to control its own operation (register 5/6), INMBSDAI001R000 can calculate the
required temperature setpoint needed to apply the decrease/increase on the real
temperature and reach the temperature chosen by the user (following the example
above, if INMBSDAI001R000 reads an “ambient temperature” (register 5/6) of
24ºC in the indoor unit, it will apply a final setpoint of 24ºC + 2ºC = 26ºC).
o At this moment, each time that INMBSDAI001R000 detects a change on the
ambient temperature reported by the indoor unit (register 5/6), it will also change
the required setpoint, in order to keep the temperature required by the user at any
time. If we follow the last example, if INMBSDAI001R000 receives a new
temperature´s value coming from the indoor unit of 25ºC, INMBSDAI001R000 will
automatically adjust the temperature setpoint required of the AC indoor unit to
25ºC + 2ºC = 27ºC).
o After the startup, the value for “external temperature’s reference” (register 22/23)
has a value -32768 (0x8000). This value means that no external temperature
reference is being provided through INMBSDAI001R000. In this scenario, the
setpoint value shown in register 4/5 is always the same as the current setpoint
value of the indoor unit. The AC indoor unit will use its own return path temperature
sensor as reference for its control loop.
o When the mechanism of “Virtual Temperature” is applied, the temperature
setpoint’s value shown by the Remote Controller or other Control System from
Daikin connected to the indoor unit may show a different value from the value
shown in register 4/5.
• AC Real temperature setpoint (R)
(register 23 – In Protocol address / register 24 – in PLC address):
As it has been detailed on the previous point, the real temperature setpoint in the indoor
unit and the temperature setpoint requested from INMBSDAI001R000 might differ (when
a value in register 22/23 – “external temperature reference” is entered and virtual
temperature is applied).