99
Control units VCS
PLC Controller for Compressor Output Control
Safety Measures
Check the correct supply voltage (see Technical Data) before
connecting the device. Do not expose the device to moisture
or water. Use the devise so that the operating conditions
will not be exceeded and the device will not be exposed to
abrupt changes in temperatures at high humidity causing air
humidity condensation.
Warning: Disconnect all power supply connections before you
start any maintenance work on the device.
e sensors must be located out of reach of the end user. Do
not disassemble the device. If the device fails or malfunctions,
send it back, including a detailed description of the failure.
General Description
e PLC controller controls cooling in the air-conditioned room
depending on the signals received from the parent system
and pre-set parameters. It measures temperature in the
compressor discharge and pressure in the heat exchangers.
If the device is fitted with a 4-way valve (Premium" version),
it is possible to switch the unit between cooling (in summer)
and heating (in winter) modes of the ventilated room, including
heat recovery. For a more detailed description of this technol-
ogy, refer to the User Manual. e device is equipped with
preparations for a differential pressostat in the air-handling
unit channel, serving as antifreeze protection of the evapora-
tor. e signal received from this switch will start defrosting
by directing inlet air to the evaporator's fins. Defrosting starts
automatically if the limit evaporation temperature is set below
4°C, when ice build-up is created on the evaporator's surfaces
which need to be defrosted. If the differential pressostat is not
present, defrosting can also be set for time cycles using the
parameters. Evaporation pressure is used to monitor the de-
vice and the unit's output is reduced to protect the evaporator
against freezing at low evaporation temperatures. Condensa-
tion pressure monitoring is another way of providing device
protection. When this value is increased, the unit's output is
reduced to prevent a failure. e output reduction is signalled
by the relay contact – KA7. e output reduction level can also
be signalled by 0-10V analogue outputs. One signal's reduction
is based on the evaporation temperature and the other one is
based on the condensation temperature. e device is able to
control condensation pressure using an analogue output. is
feature is only available for the "Premium" version.
Process Control
Control is started as soon as the contacts for the unit start are
closed. Relay – KA9. If the unit is equipped with reversation,
the cooling or heating mode is selected.
LED Mode Function
On Unit start is requested
On Cooling in operation
On Heating in operation
On Defrosting in progress
On Power valve switched on
On Alarm
On No function
On Measured units
On Programming Menu
Flashes
Remembers the Prog. Menu password
for 60 s
1 FA1 circuit breaker open
2 FA2 circuit breaker open
3 Low-pressure pressostat open
4
High-pressure pressostat open or
incorrect phase sequence
5 Electronic injection valve failure
6 Output limiting relay closed
e selection is made by the relay – KA11 (closed = heating).
en the unit output is controlled by the 0-10V analogue
signal. Operation of the unit is indicated by a dry contact,
the same way as an error. e unit is equipped with several
protections, protecting the cooling device against damage
(pressure switches, outlet temperature monitoring, etc.).
Controller Operation
SET(F4) Shows the user parameters.
In the programming mode, it is used to select
the parameter or confirm the operation.
ESC(F2) In the programming mode, it is used to cancel
the operation. Cancels the action.
Long hold = Failure reset
(F1) No Function
(F3) No Function
Key combination:
SET(F2) + Esc (F4) Enters the programming mode.
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