10
Main Control Feature and
Protection Description
Using the appropriate sensors, the VCS control unit can
provide comprehensive protection of the air-handling unit,
such as active antifreeze protection, fan state monitoring,
filter fouling or over-temperature detection of the required
temperature. Any deviations from the defined states or
parameters are monitored and signalled and simultaneously,
safety features are activated.
Depending on the failure consequence, the following happens:
n e failure is only signalled and safety features are automati-
cally activated. Once the failure has ceased, the unit will return
to the standard mode without interference from the operator.
n If a serious failure occurs, the unit will be switched to
the STOP mode, and it can only be restarted after the
failure has been removed and the operator's interference.
e VCS control unit system enables the air-handling unit
behaviour (fan action) to be set when fire is detected
(external failure, inlet or outlet air high temperature).
The settings can be as follows: the inlet or outlet fan is
activated, both fans are activated or both fans are stopped
(air-handling unit shutdown). e control unit is switched to
the fire mode. e settings can be performed using the HMI
controller in the List of Data Points, section Checks, System
and Network Settings – Fire Alarm.
Heating Control
Control is based on the required temperature, i.e. the selected
temperature mode and data from the supply air temperature
sensors, outdoor temperature and the water heat exchanger
return water temperature. Control can be affected by cor-
rection values, maximum and minimum limits or antifreeze
protection.
Water heating
It is controlled by the SUMX mixing set actuator using a 0–10V
continuous control signal (working range of 2–10V).
Heating Mixing Set Pump Control
e mixing set pump is controlled depending on the outdoor
temperature value and valve position (required heater output).
n If the air-handling unit is in the STOP and Run mode, the
pump is switched on when the outdoor temperature drops
below 5°C and switched off when the outdoor temperature
rises above 6°C. In this case, the pump is stopped without
any run-down.
n If the air-handling unit is in the Run mode, the pump is
controlled by the valve actuator control algorithm. e pump
is switched on when the request for the valve opening is
higher than 5%.
n If the pump has not been used for 168 hours, it will be
switched on and turned for 60 seconds.
n Failures (electrical) of the pump are sensed by the pump
circuit breaker’s auxiliary contact even in the STOP mode.
Water Heater Antifreeze Protection Operation
e VCS control unit uses so-called active antifreeze protec-
tion. It uses a three-stage concept.
Antifreeze Protection Features:
Control and Protection Functions
Note: is chapter describes only the basic control functions
– the detailed design, respectively compatibility, of the entire
device is ensured by the configuration performed using the
AeroCAD design soware. For more detailed information,
contact the manufacture, REMAK a.s.
Main Control Features
e VCS control unit enables automatic control of the follow-
ing basic functions for air temperature adjustment:
n Heating
n Cooling
n Mixing
n Recuperation (Heat Recovery)
n Dehumidification
n PID controllers with pre-set control constants are as-
signed for all the above-mentioned functions. Basic settings
of parameters are performed in the factory. e parameters
can be changed using the HMI controller in the List of Data
Points menu, item Control Constants.
n A check, respectively optimization, of the unit settings must
always be performed when commissioning the unit.
n Control ensures energy-saving operation. Cascade tem-
perature control – room temperature control or supply air
temperature control.
n e required temperature for the air-conditioned room
can be set by selecting one of two temperature modes. Each
mode has two pre-set temperature values to maintain the
required temperature (an upper limit for heating and a lower
limit for cooling). ese values can be changed using the HMI
controller in the List of Data Points, section Settings – Tem-
perature Modes.
n First, the control algorithm will start to control the functions
which don't require energy, i.e. heat-recovery and mixing (de-
pending on the user option). If this is not enough to maintain
the required parameters or these features are not included in
the air-handling unit, heating and cooling functions will be ap-
plied. If the heating or cooling control is not effective enough,
an air output control will be added (heating/cooling-dependent
fan speed compensation – user option). is control does not
allow heating and cooling to be used at the same time, only
one control sequence can be used at a time. is does not
apply for special control application with controlled humidifi-
cation where a cooler can be used for dehumidification and a
heater for aer-heating to the required temperature.
Heat pump, water and electric heater or gas heater functions
can be connected to the heating control sequence. Heat pump,
water cooler and condenser unit functions can be connected
to the cooling control sequence.
Temperature Correction and Limitation
The control unit enables adjustment and settings of the
restricting limits for maximum and minimum supply air
temperatures. In addition, it is possible to set the supply air
and room temperature limits, respectively other correction or
comfort options (e.g. set-point value compensation or heat-
ing/cooling-dependent fan speed compensation).
Control and Protection Functions
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