Carel k.Air, User Manual, Page: 62 / 192

62
Functions
k.air +030220981 rel. 1.2 - 01.12.2020
Operating mode
The main coil is the only device that can optionally work in both heating and cooling mode. The modes can be selected on
screen Da01: cooling, heating or heat/cool, which determines their operation as a mixed coil or reverse- cycle direct expansion
coil. On the preheating and reheating coils only heating mode is available, and therefore the mode is not confi gurable.
Modulating water coil
This coil requires management of a modulating output for the mixing valve and management of the pump assembly, which
includes management of rotation of up to two pumps with thermal protector and fl ow switch. The mixing valve follows the
percentage request sent by the controller, while the pumps are activated when the request is at least 5%, to avoid on-off cycles
at loads close to zero. If there are two pumps, one remains in standby, ready for use in the event of a fault on the pump that is
running (fl ow switch or thermal protector), while still being operational due to rotation between pumps and anti-seize function.
The rotation time between pumps, the fl ow control times and enabling of the anti- seize function can all be set by parameter.
The anti-seize function, which involves forcing the pump on for 30 s, is activated after a fi xed time of one week of inactivity.
A further option available is control of the coil supply water temperature. k.air activates an alarm on exceeding a high or low
temperature threshold, after a settable delay. An action can be set in response to the alarm, selected from the following:
• Signal only
• Complete opening of the valve and changeover to the next control device, if available
• Closing of the valve and changeover to the next control device, if available
When make the selection, take into account the positioning of the sensor with respect to the valve.
Coil with power modulation
This type of coil is typically used for electric heaters, but can also be used as an external control signal when the main coil is
in cooling mode. A modulating output and up to four on/off stages are available. For electric heaters, in the maximum confi -
guration, a modulating device can be fi tted on one heater, with three additional heaters activated sequentially once the fi rst
has reached maximum power. The heating capacity of the stages must be the same, and no rotation is featured to balance the
operating hours. To avoid unnecessary on-off cycles, there is a 5% hysteresis in transitions between the stages. The image below
shows the activation sequence for the maximum system confi guration
30220980_194_R01
TotRegReq
ModOut
Step 1
Step 2
Step 3
Step 4
0
100
Fig. 9.r
Coil with progressive steps
Typically used for on/off heaters, but also available for any non-modulating device, this coil uses up to four power steps. The on/
off outputs provided correspond to the number of control steps. The control request is divided equally into the number of steps
set, with a hysteresis between steps equal to the power of each step as a percentage. The image below shows the activation
sequence for the maximum system confi guration of four steps.