Carel k.Air, User Manual, Page: 74 / 192

74
Functions
k.air +030220981 rel. 1.2 - 01.12.2020
30220980_175_R01
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
xg
/k
g
T_dew_pt
Fig. 9.ae
Note: for both control functions, dehumidifi cation mode acts on the cooling coil only when the unit is in dehumidifi cation
status. This status is activated when the humidity control request is greater than 20%. Dehumidifi cation status is visible in the
unit status information on the main screen.
9.16 F reecooling/free heating
Freecooling and freeheating are free energy sources, activated with priority in cascade control in cooling and heating mode. The
freecooling/freeheating functions are enabled when the following conditions have been verifi ed:
• Return or room temperature probe available
• Outside air temperature probe available
• Modulating dampers, modulating fans or both available
The freecooling/freeheating request from the fi rst stage of the main temperature sequential PID is used to gradually open the
fresh air damper and subsequently increase the fan speed, always in accordance with the fan operating mode. Fixed speed
fans are activated at maximum speed. For fans with pressure/fl ow control, the speed increases due to an increase in the set
point (similarly to what happens for air quality control). Use of dampers is enabled on screen Ca12, and use of freecooling via
ventilation on screen Ba15.
The freecooling/freeheating request is always subject to verifi cation of the activation conditions, based on the outside air tem-
perature and return/room temperature.
9.16.1 A ctivation conditions
Freecooling can only be activated if an outside air temperature probe is available, without alarms, and the outside air tempe-
rature measured diff ers from the control temperature (room or recovery) by a certain set delta.
Note : the following graphs assume a fi xed outside temperature.
FREECOOLING (cooling requestactive)
30220980_170_R01
OFF
Set
RetT ExtT
ON
T
Enable
delta_fc
30220980_169_R01
OFF
Set
RetT ExtT
ON
T
Enable
delta_fc
Key
RecT Return temperature
ExtT Outside temperature
T Temperature
Set Set point
delta_fh Freeheating activation delta
delta_fc Freecooling activation delta
Fig. 9.af
ON : RetT-ExtT> delta_fc ; OFF : RetT-ExtT<0