Carel k.Air, User Manual, Page: 59 / 192

59
Functions k.air +030220981 rel. 1.2 - 01.12.2020
Supply temperature limit control
The algorithm corrects the actions implemented by the main control function so as to remain within acceptable supply tempe-
rature values. This occurs, and is a required condition, when the main temperature control is not supply temperature control.
The function uses a minimum and a maximum limit, with diversifi ed actions according to the operating mode, heating or co-
oling.
Low temperature limit High temperature limit
Heating
mode In the event where the return set point has been reached but there
is an active air quality control request. This leads to the introduction
of cool outside air below the minimum limit. The limit function will
thus increase the output of the heating devices. Return temperature control may lead to the introduction of
excessively hot air, due for example to overloading of the
heating coils.
The limit function will thus gradually reduce the output of
the heating devices.
C ooling
mode
Return temperature control may lead to the introduction of
excessively cold air, due for example to low outside temperatures
or overloading of the cooling coil.
The limit function will thus gradually reduce the output of the
cooling devices (coils and freecooling) and subsequently activate
the heating devices, where available. In the event where the return set point has been reached
but there is an active air quality control request. This leads
to the introduction of excessively hot outside air, above
the minimum limit. The limit function will thus increase the
output of the cooling devices.
Tab. 9.k
The minimum and maximum supply limits are available in loop A.Unit> C.Confi g and are always visible. It is possible to set a gain
and integral time to calibrate the response of the limit control function.
The same thresholds are also used as an alarm that, with a suitable delay at start-up/in steady state, shuts the unit down (OFF)
when reaching the minimum limit in cooling mode and the maximum limit in heating mode. In other cases, the alarm does not
shut the unit down and is signal-only.
For adiabatic humidifi cation, the production of humidity is also limited as the last stage of the low supply temperature limit
function. This accessory function is also active, as the only limit stage, in the main supply temperature control function. Below is
a summary of the limit action.
Main control, return or room temperature Main control, supply temperature
Heating
mode The limit function is active as the last stage; after increasing the output of
the heating devices, adiabatic humidifi cation output is reduced The limit function reduces adiabatic humidifi cation
output only
C ooling
mode
The limit function is active as the last stage; after increasing the output of
the cooling devices, adiabatic humidifi cation output is reduced The limit function reduces adiabatic humidifi cation
output only
Tab. 9.l
R if D escription D ev Min Max UoM D ir Modbus BAC net
U N IT
Ac60 Low supply temperature threshold 16.0 0.0 25.0 °C R/W HR1354 AV2862
Low supply temperature alarm delay time at start up 999 0 65535 s R/W HR1355 PIV2863
Low supply temperature alarm delay time at unit in run mode 600 0 65535 s R/W HR1356 PIV2864
Ac62 High supply temperature threshold 32.0 0.0 40.0 °C R/W HR1357 AV2865
High supply temperature alarm delay time at start up 999 0 65535 s R/W HR1358 PIV2866
High supply temperature alarm delay time at unit in run mode 600 0 65535 s R/W HR1359 PIV2867
Ac64 Low supply temp: proportional part 8.0 0.0 999.0 - R/W HR1360 AV2868
Low supply temp: integral time 120 0 999 s R/W HR1361 PIV2869
Ac66 Purge function - Time 10 0 999 min R/W HR1949 PIV3972
Purge function - Automatic mode 0 0 3 - R/W HR1950 PIV3973
Purge function - Start hour 0 0 23 h R/W HR1951 PIV3974
Purge function - Start minute 0 0 59 min R/W HR1952 PIV3975
Tab. 9.m
9.7 C ooling and heating
The k.Air controller is extremely fl exible in adapting to the temperature control demands and characteristics of the system so as
to respond to changes in season or over a day. The unit can operate (Ac22):
• In cooling only mode;
• In heating only mode;
• With heating/cooling changeover (manual or automatic)
If the unit is set for heating/cooling changeover, diff erent types of transition can be selected between cooling and heating, as
shown in the following table:
Type of heating/cooling changeover D escription N ote
Manual from DIN The unit changes mode based on the status of the selected digital input
Manual from keypad The unit changes mode when selected on the display (Qc04)
Manual from BMS The unit changes mode when selected on the supervisor see register in supervisor
table (retentive register)