Low Dehumidification Temperature Limit; Timed Dehumidification Function; Post - Heating - Mitsubishi Electric s-MEXT-G00 006 Technical Manual

TM_s-MEXT_ME28relC_00_12_19_EN
7.2.5

Low dehumidification temperature limit

In case of a direct expansion unit, there is another limit above which, irrespective of whether there are any heating/post heating resources, the dehumidification function is
immediately inhibited.
This limit keeps the unit from operating under low evaporation conditions.
The parameter for the definition of the low temperature limit can be found in the "Setpoint" menu. The lower limit of this parameter is defined by the low temperature
minimum limit parameter in the "Safety" menu, which can be accessed by entering the "Factory" password.
For the default values, see the parameters table.
7.2.6

Timed dehumidification function

For direct expansion units, another function is added in order to time the operation of the dehumidification.
The following graph shows how this function works.
Dehumidification therefore remains enabled for a time equal to the "Max DH time" parameter (expressed in minutes). When this time elapses the compressor is disabled for a
time equal to the "Max waiting time" parameter (expressed in minutes) and then compressor operation is enabled once again.
The parameters used to configure this function are under the "Safety" menu, which can be accessed by entering the "Factory" password.
For the default values, see the parameters table.
7.2.7

Post - heating

If heating resources are present it is possible to enable them for post-heating, that is, heating the air after it crosses the cooling coil. This makes it possible to avoid
prematurely interrupting the dehumidification function to reach the previously described lower limit.
For this purpose, the activation of the heating resources must not be distributed inside the heat differential band as it would be expected for heating as, in this case,
maximum heating power would occur simultaneously with dehumidification disabling
Therefore, the heating power must be distributed over an ambient temperature band, so that the maximum heating power occurs at a value that is not only higher than the
previously indicated lower limit, but also relatively distant from the same.
This allows the heat resources, after being enabled, to effectively change the ambient air temperature before it reaches the lower dehumidification limit. This is particularly
important in small environments, where the activation of the dehumidification causes a quick decrease of the temperature.
As a result, the post-heating resources are enabled in sequence on the first half of the heating band, as shown in the following figure.
The resources, if present, can be selected from the "Optional" menu, which can be accessed by entering the "Service" password.
The Cooling Setting parameter is under the "Set point" menu. The cold setting parameter is under the "Regulations" menu, which can be accessed by entering the
"Service" password .
Technical manual
P50.09
ON
OFF
P14.11
P14.12
Figure 7-6: Timed dehumidification adjustment graph
Step 3
Step 2
P50.02 +
2/6
P20.19
1/2
P20.19
Figure 7-7: Post heating resource management
T
ambien t
Compressor
P14.11= Maxi m um dehumidification cycle ON time
P14.12= Minimum delay for new dehumidification cycle
Step 1
P50.02 +
P50.02 T (°C)
ambient
1/6
P20.19
81
(°C)
Time (min)
TRANSLATION OF THE ORIGINAL INSTRUCTIONS