Carel kVent Manual page 23

ON time
Recovery
Period fixed to 10minutes
Request
10min
0min
5.7.2 Hydronic circuits in heating
The PID sequence calculates a request 0-100% that is directly
executed by the valves, but in case of water antifreeze
prevent, the water valve opening increase, according to
antifreeze setpoint. For antifreeze details check the related
chapter.
Here below the regulation of water devices:
Valve
Min.
100%
A018
Min. signal
A022
Pump
In case of external temperature below the force heating
threshold (H012), the pump is ON all the time to measure the
back water temperature and be sure that water is above the
antifreeze limit (A019). Water valve is closed, so there isn't
heating effect on the unit.
5.7.3 3 point valve or damper
In case of water circuits or modulating dampers, kVent can
provide the 3 point control.
Two digital outputs are provided to open or close the valve.
According to percentage request and valve opening time, the
digital outputs act to follow the request. To avoid stressed
regulation and too many valve actuations, a deadband is
provided. If the request reaches 100%, the opening valve is
kept for a while to ensure the valve is at maximum opening.
Same management, but with closing valve, in case the request
reaches 0%.
5.7.4 Heaters
Heaters could be present according application code in main,
preheat and reheat sides. The PID sequence calculate a
request 0-100% that is directly executed by the heaters.
Maximum heaters managed are 2 ON-OFF and 1 modulating.
kVent needs the power of each heater to divide the power in
the best way.
The modulating device has the highest priority and there isn't
any rotation, but in case of devices with different power, the
priority of ON-OFF devices can change to satisfy in the best
way the request by thermoregulation.
Here below an example with devices with the same power:
Min inverter power: 20%
Max heaters power: 33.3kW
In this case the second heater will start when the request
reach the threshold calculated in the following way:
kVent – rel 3.1 – 22/06/2018
OFF time
100%
ON time
OFF time
33.3
42.67 %
33.3
Before to start the ON-OFF device, the request must be
greater than 20% of the power of the second device.
Here below the graph:
100%
Min
0%
It's possible to set different power of the heaters (A025, A026,
A027), so the ON sequence will be different to follow the
request from PID loop.
5.7.5 Direct expansion (DX)
Below the description of how the direct expansions circuit
works in the application. DX could be present according
application code in main cool, main heat, reverse, preheat and
reheat sides.
The PID sequence calculate a request 0-100% that is
executed by ON-OFF devices and by a modulating device.
Each ON-OFF device has a threshold to start the device and a
threshold to stop the device.
The modulating element will follow the request from PID
sequence.
100%
0%
Start 2
Start 1
Between the stages activation there is a timings control, listed
below:
Stages activation Start 1
Heating A031
Cooling B015
Reverse C053
Timings settings Min ON
Heating A028
Reheating A040
Postheating A051
B011
Cooling
Reverse C050
In case of cooling DX, is possible to disable the cooling DX
devices in ECO and PRECOMFORT modes (B014).
5.7.6 Steam
Steam device could be present in the main heater only.
The PID sequence calculate a request 0-100% that is directly
executed by the steam actuator.
Here below the regulation of device:
23
!∗ ##.#$#.##
3.33
%!!
∗ 100%
33.3 33.3
42.624
∗ 100%
99.9
Modulation signal
ON/OFF steps
Stop 2
Stop 1
Stop 1 Start 2
A032 A033
B016 B017
C054 C055
Min OFF Between device
A029 A0030
A041 A042
A052 A053
B012 B013
C051 C052
Stop 2
A034
B018
C056