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5.11 - DEFROST FUNCTION
Defrost is activated, when the unit is in heating mode, in
order to reduce frost build-up on the air heat exchanger.
The defrost cycle can only be applied to one circuit at a
time. During the defrost cycle the fans of that circuit are
stopped, and the fourway refrigerant valve is reversed,
forcing the circuit to cooling mode. The fan can
temporarily be restarted during the defrost cycle. The
defrost cycle is fully automatic and does not require any
setting.
5.12 - ADDITIONAL ELECTRIC HEATER STAGE
CONTROL
The heat pump units can control up to four additional
electric heating stages.
✓
The unit uses 100% of the available heating capacity,
or the unit is limited in its operation by a protection
mode (low suction temperature, hot gas or defrost
sequence in progress protection), and in all cases
cannot satisfy the heating load.
✓
The outdoor temperature is below a configured
threshold (see User 1 configuration).
✓
The unit demand limit is not active.
The user may configure the last available electric heating
stages as a safety stage. In this case, the safety stage is
only activated in addition to the other stages if there is a
machine fault, preventing the use of the heating capacity.
The other electric heating stages will continue to operate
as described above.
5.13 - CONTROL OF A BOILER
NOTE:
The control of the electric heating stages or of a
boiler is not authorised for slave units.
The unit can control the start-up of a boiler, if it is in
heating mode. When the boiler is operating, the unit water
pump is stopped.
A heat pump unit and a boiler cannot operate together.
In this case the boiler output is activated in the following
conditions:
✓
The unit is in heating mode, but a fault prevents the
use of the heat pump capacity.
✓
The unit is in heating mode, but works at a very low
outdoor temperature, making the heat pump
capacity insufficient. The outdoor air temperature
threshold for use of the boiler is fixed at -10°C, but
this value can be adjusted in the User 1 menu.
5.14 - MASTER/SLAVE ASSEMBLY
Two PRO-DIALOG Plus units can be linked to produce a
master/slave assembly. The two machines are
interconnected over the CCN bus. All parameters required
for the master/slave function must be configured through
the Service configuration menu. Master/slave operation
requires the connection of a temperature probe at the
common manifold on each machine, if the heat exchanger
leaving water temperature is controlled.
The master/slave assembly can operate with constant or
variable flow. In the case of variable flow each machine
must control its own water pump and automatically shut
down the pump, if the cooling capacity is zero. For
constant flow operation the pumps for each unit are
continuously operating, if the system is operating. The
master unit can control a common pump that will be
activated, when the system is started. In this case the
slave unit pump is not used.
All control commands to the master/slave assembly (start/
stop, setpoint, heating/cooling operation, load
shedding, etc.) are handled by the unit which is
configured as the master, and must therefore only be
applied to the master unit. They will be transmitted
automatically to the slave unit. The master unit can be
controlled locally, remotely or by CCN com-mands.
Therefore to start up the assembly, simply validate the
Master operating type (MASt) on the master unit. If the
Master has been configured for remote control then use
the remote voltfree contacts for unit start/stop. The slave
unit must stay in CCN operating type continuously. To
stop the master/slave assembly, select Local Off (LOFF)
on the master unit or use the remote volt-free contacts if
the unit has been configured for remote control.
One of the functions of the master unit (depending on its
configuration) may be the designation, whether the master
or slave is to be the lead machine or the follower. The
roles of lead machine and follower will be reversed when
the difference in running hours between the two units
exceeds a configurable value, ensuring that the running
times of the two units are automatically equalised. The
changeover between lead machine and follower may take
place when the assembly is started up, or even whilst
running. The running time balancing function is not acti-
ve if it has not been configured: in this case the lead
machine is always the master unit.
The lead machine will always be started first. When the
lead machine is at its full available capacity, start-up
delay (configurable) is initialised on the follower. When
this delay has expired, and if the error on the control
point is greater than 1.7°C, the follower unit is authorised
to start and the pump is activated. The follower will
automatically use the master unit active setpoint. The
lead machine will be held at its full available capacity for
as long as the active capacity on the follower is not zero.
When the follower unit receives a command to stop, its
evaporator water pump is turned off with 20 seconds
delay.
