Considerations On Temperature Registers - IntesisBox ME-AC-MBS-1 User Manual

4.2.3 Considerations on Temperature Registers

• AC unit temperature setpoint (R/W)
(register 4 – in Protocol address / register 5 – in PLC address):
This is the adjustable temperature setpoint value that must be required by the User. This
register can be read (Modbus function 3 or 4) or written (Modbus functions 6 or 16). A
Remote Controller connected to the Mitsubishi indoor unit will report the same
temperature setpoint value as this register. This will apply when no AC unit's external
reference temperature is provided from ME-AC-MBS-1 (see details for register 22/23
below).
• AC unit temperature reference (R)
(register 5 – in Protocol address / register 6 – in PLC address):
This register reports the temperature that is currently used by the Mitsubishi indoor unit
as the reference of its own control loop. Depending on the configuration of the indoor
unit, this value can be the temperature reported by the sensor on the return path of the
Mitsubishi indoor unit or the sensor of its Remote Controller. It is a read-only register
(Modbus functions 3 or 4).
• AC unit external temperature reference (R/W)
(register 22 – in Protocol address / register 23 – in PLC address):
This register allows us to provide an external temperature's sensor from the Modbus
side. Mitsubishi indoor unit does not allow, on devices like ME-AC-MBS-1, to provide
directly a temperature to be used as a reference of the control loop of the AC indoor
unit. In order to overcome this limitation and enable the usage of an external
temperature sensor (e.g. from Modbus side), ME-AC-MBS-1 applies the following
mechanism (only if "external temperature's reference" is being used):
After a couple of values have been entered in the "AC unit external temperature's
o
reference" (register 22/23) and the "AC unit temperature set point" (register
4/5), ME-AC-MBS-1 calculates the corresponding temperature's demand (e.g., if
a "temperature setpoint (register 4/5)" of 22ºC, and an "external temperature
reference (register 22/23)" of 20ºC are entered, ME-AC-MBS-1 will assume that
the user is demanding a +2ºC increase in temperature).
By knowing at any time the ambient temperature currently used by the indoor
o
unit to control its own operation (register 5/6), ME-AC-MBS-1 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 ME-AC-MBS-1 reads an "ambient temperature" (register 5/6)
of 24ºC in the indoor unit, it will apply a final setpoint of 24ºC + 2ºC = 26ºC).
At this moment, each time that ME-AC-MBS-1 detects a change on the ambient
o
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, when ME-AC-MBS-1 receives a new
temperature´s value coming from the indoor unit of 25ºC, ME-AC-MBS-1 will
automatically adjust the temperature setpoint required of the AC indoor unit to
25ºC + 2ºC = 27ºC).
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ME-AC-MBS-1
User's Manual r21 EN
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