ENG
“FLSTDMAHUE” +030220961 - rel. 1.1 - 28.08.2019
38
2.
dew point:
Screen index
Display description
Selection
Ha06
Dehumidification
Dew point
The dehumidification request is managed based on the humidity set point
and the differential, according to the humidity measured by the control
probe. Once the request is received, the controller uses the dew point
calculation, and based on the humidity and temperature set point controls the
cooling actuator, comparing against the value measured by the temperature
probe downstream of the coils. As soon as the humidity probe detects a
dehumidification request, the control calculates the final dewpoint and sets
this as the temperature set point (T_set_R) after the cooling coil.
100%
0%
Dew_point
Sat_probe (°C)
Min_op_dehum
A
Diff_cool
Key
A
Cooling actuator opening
Dew_point
Dewpoint
Sat_probe Saturation probe
Min_op
Coil minimum opening
Screen index
Display description
Def
Min
Max
UOM
Gfc05
Cooling control
Differential
2
0
99.9
°C
Psychrometric diagram
0
5
10
15
20
25
30
35
40
45
-5
0
5
10
15
20
25
30
35
40
45
50
55
DBT °C
x g
/k
g
T_set_R
T_set_T
Key
T_set_R
Dew point
T_set_T
Temperature set point
3.
specific humidity
Screen index
Display description
Selection
Ha06
Dehumidification
Specific humidity
The relative humidity probe needs to be installed downstream of coils and
activated. Specific humidity is calculated based on relative humidity and
temperature. The coil cools until the specific humidity reaches the set point.
The advantage compared to the previous case is less need for reheating, as it is
not necessary to cool down to the dew point (T_set_R, see figure).
Psychrometric diagram
0
5
10
15
20
25
30
35
40
45
-5
0
5
10
15
20
25
30
35
40
45
50
55
DBT °C
x g
/k
g
T_set_T
Specific
humidity
T_set_R
Key
T_set_R
Dew point
T_set_T Temperature set point
Dehumidification based on absolute humidity requires the setting of several
control parameters: maximum and minimum limit based on the season,
differential and integral time. The limits are also active with supply humidity
control, meaning supply relative humidity control is possible with limits in
terms of specific humidity.
Screen index
Display description
Def
Min
Max
UOM
Gfc13a
Supply specific humidity limits
Summer high
15
0
100
g/Kg
Winter high
15
0
100
g/Kg
Summer low
5
0
100
g/Kg
Winter low
5
0
100
g/Kg
Differential
0
0
100
g/Kg
Integral time - Ti
0
0
100
g/Kg
For all dehumidification methods, the reheating coil will be activated to
offset cooling, as shown in the table.
Reheating control
No. Control
Preheating
coil
Cooling coil
Reheating coil
1
Dehumidification
without tempera-
ture request
Deactivated Control based
on humidity
control probe
or probe
downstream
of coil
For return control, the supply
temperature set point is equal
to the return temperature set
point (cooling neutralised
during dehumidification). For
supply control, control is based
on supply conditions.
2
Dehumidification
with cooling
request
Deactivated Control based
on higher of
two required
Control based on supply probe
with set point and differential
equal to minimum supply limit
9.5 Temperature / humidity control / no
priority
To control temperature and humidity, the coils and the humidifier must be
enabled and the types must be set. The following also need to be activated
and set:
1.
the temperature and humidity control probes;
2.
the dehumidification function and mode;
3.
the humidifier and control probe;
4.
the temperature and humidity set points.
Simultaneous requests for:
1.
heating and humidification;
2.
dehumidification and cooling:
are not incompatible as regards activation of the devices, consequently
if a priority has been set the controller will try to satisfy both requests. If
this involves the same actuator, the latter operates based on the higher
of the two requests. To prevent uncomfortable situations being created,
the “supply limits” function can be used.
On the other hand, in the event of simultaneous requests for:
1.
heating and dehumidification;
2.
cooling and humidification, control is performed according to the table
below, based on the priority: temperature, humidity or none.
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