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Control and Protection Functions
the difference between these two temperatures is at least 1 °C.
Heat recovery and mixing functions will be switched off when
the outdoor temperature is lower or equal to the room (outlet
air) temperature, or the room (outlet air) temperature is higher
or equal to the required room temperature. Heat Exchanger
control function activation settings are described in the chapter
Additional Operating Mode and Function Setting Options.
Heat Recovery and Mixing Control
at Air-Handling Unit Start-Up
The starting outdoor temperature and time are set for heat
recovery and mixing (see Data Points). If the outdoor temperature
is lower than the pre-set value at the air-handling unit start-up,
the heat recovery and mixing functions will be switched on at
the maximum level.
Mixing Sequence Selection
The mixing sequence for heating control is optional – the pre-set
sequence for heating is as follows: first, the mixing function is
applied and if the request for heating still increases, then the
heating function will be applied (pre-set). This sequence can be
changed according to user needs, see the chapter Additional
Operating Mode and Function Setting Options.
Humidity Control
The control unit evaluates the control signal for humidification
or dehumidification depending on the room and inlet humidity
sensors and the required humidity selected by the user.
Humidification
Humidification control can be ensured by two methods. Depend-
ing on the technology used, control for the required humidity
can be performed by the VCS control unit or by an autonomous
control (e.g., integrated into the humidifier).
In the first case, humidity control is ensured by the VCS control
unit. Settings of humidity set-points and control parameters are
included in the VCS control unit. The same applies for dehumidi-
fication. Thus, full accord of dehumidification and humidification
control is ensured and unsuitable settings of set-points cannot be
made. Furthermore, all the necessary parameters and informa-
tion can be found in the control unit controllers. The control unit
sends the start command, the request for humidification output
to the humidifier, and monitors humidifier failures.
If autonomous control is used, the control unit sends information
on the air-handling unit operation to the humidifier. In this case,
control for the desired humidity is fully ensured autonomously by
a specific humidifier. The control unit has no information about
the state or output of the humidifier.
Dehumidification
Air dehumidification is ensured by water or direct cooling. In case
of dehumidification, after-heating is ensured by the heater, which
is situated after the cooler. The control unit evaluates the control
signal for the air cooler and heater depending on the room sen-
sors and the required humidity selected by the user. The humidity
in the room can be set from 20% to 95%. If the air-handling unit
is equipped with a water cooler or a condensing unit with an
inverter, the humidification process can be controlled using 0–10
V (2–10 V) step-less control. If the air-handling unit is equipped
with a one-stage or a two-sage condensing unit, the humidifica-
tion process is controlled using step control. When cooling is
active due to a request for dehumidification, air after-heating is
Control units VCS
allowed (exceptionally) using the heater situated after the cooler.
If the request for heating is increased above 90 %, the request for
dehumidification cooling is gradually reduced until the required
inlet air temperature, respectively zero value of the request for
cooling (at 100 % request for heating), is achieved – temperature
control is prioritised to humidification.
Auxiliary Control Functions
Pre-heating function
Pre-heating is switched ON/OFF depending on the pre-set
outdoor temperature value (pre-set 5 °C).
The electric pre-heater (EO) is switched using a contactor. It is
controlled according to the pre-set (required) temperature and
compared with the temperature behind the preheater (measured
by the NS 120 sensor). If the air-handling unit is switched off
when the EO pre-heater is active, run-down of the fans will be
performed. Failures are evaluated similarly as with EO heaters
but the system is not shut down.
Water pre-heating is controlled by switching the pump (not
included in the REMAK delivery) depending on the request for
pre-heating. Antifreeze protection is ensured by a temperature
sensor (NS130R) situated in the water heat exchanger return
line. If the water temperature in the water heat exchanger's
return line drops below the pre-set value, the freezing alarm will
be activated, including safety functions, and the air-handling unit
will be stopped.
Auxiliary After-Heating
Function – electric/water
This function is applied when the main heater output is not suf-
ficient (e.g. when water heating is shut down during transition
seasons, etc.) It is possible to restrict the maximum electric
after-heater output for each output stage. Thus correct cooling
of the heating rods is ensured (see the Data Points). The electric
after-heating function can also work as an independent sequence
with its own settings of required temperatures. The electric after-
heating function is disabled in the following cases:
n
When night chilling is active
n
During temperature start-up
Heating Water Source Switching
The hot water demand is evaluated by one of the following
conditions:
1) The controller evaluates the heating water demand. The
outdoor temperature is lower than the set (calculated) supply air
temperature (air heating demand arises).
2) The outdoor temperature is lower than the limit value
for heating (see data points - switching parameter of the
heating water source). Factory setting 15 ° C.
3) If a freeze is declared on water or in the air.
This switches on the output for switching the heating water
source (boiler) - in the case of starting the device in advance
before starting the fans. The correct functionality of the system
must be ensured by suitable setting of the related parameters
of the device start sequence. To use the switching function
of the heating water source, the outdoor temperature sen-
sor must be installed so that it actually senses the outdoor
temperature.
15
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