o In general, INMBSMIT001I000 is constantly applying the “Virtual Temperature”
formula:
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 INMBSMIT001I000 detects a change in any of the values of
{ Su , Tu , TAC }, it will send the new setpoint (SAC) to the indoor unit.
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 INMBSMIT001I000. In this
scenario, the setpoint value shown or written in register 4/5 will always be the
same as the current setpoint value of the indoor unit.
o Notice that, the use of the “external temperature reference” (register 22/23)
(e.g., writing a value different from -32768 / 0x8000 in it) has the following
relevant consequences:
• The mechanism of “Virtual Temperature” is applied. The temperature
setpoint’s value shown by the Remote Controller or other Control System
from Mitsubishi connected to the indoor unit may show a different value
from the value shown in register 4/5.
• The User is not be able to change the setpoint using any Remote Controller
from Mitsubishi, as setpoint of the indoor unit becomes exclusively
controlled by the “Virtual Temperature” mechanism.
• AC Real setpoint temperature (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 indo or
unit and the temperature setpoint requested from INMBSMIT001I000 might differ (when
a value in register 22/23 – “external temperature reference” is entered). This register
always informs about the current temperature setpoint which is being used by the indoor
unit – it is also includes the temperature setpoint that will be shown by an additional
remote controller from Mitsubishi connected to the indoor unit, if it is present on the
system.
Moreover, notice that temperature’s values of all these four registers are expressed according to
the temperature’s format configured through its onboard DIP-Switches (See 3.3). The following
formats are possible:
• Celsius value: Value in Modbus register is the temperature value in Celsius (i.e. a
value “22” in the Modbus register must be interpreted as 22ºC).
• Decicelsius value: Value in Modbus register is the temperature value in
decicelsius (i.e. a value “220” in the Modbus register must be interpreted as
22.0ºC).
• Fahrenheit value: Value in Modbus register is the temperature value in
Fahrenheit (i.e. a value “72” in the Modbus register must be interpreted as 72ºF
(~22ºC).