PRO-
92
EN
running for less than a minute the system automatically re-
duces the number of start-ups but in this case the control on
the setpoint temperature is less effective.
Start-ups can be influenced by the intervention of other fun-
ctions such as defrost.
3.5.10 Night mode
This function limits machine capacity over a set period of ti-
me. The period is set by accessing the GENUNIT menu and
simply setting a start and finish time. Usually it is set for the
night time.
3.5.11 Control of optional electric heating elements
NXH units can manage up to four optional electric hea-
ting elements. Heating elements activate to compensate
the heat request to the machine in particular under these
conditions:
• When the unit is already at its full capacity or when
its capacity is reduced due to the triggering of some safety
devices
• The outside temperature value is lower than the
set threshold value (HCCONFIG menu)
• The demand limit function has not been activated.
In case more than one heating element is used, the last one
could be utilized as backup, which can be activated in case
of machine fault, supporting the other heating elements.
3.5.12 Desuperheater option
In units equipped with desuperheater it is possi-
ble to recover the heat from the hot water. The op-
tion is activated from the SETPOINT menu by setting
the min_sct parameter. It is also possible to use the
dry contacts (see inputs MENU, DSHTR_SW parameter).
3.5.13 Defrost function
It is a function present also in the NXH series machines.
It is activated when the unit is in heating mode to pre-
vent the formation of ice on the air side exchanger.
The defrost cycle is performed on one line at a time (in
case of machines with two or more lines); during the defrost
phase the fan of the line undergoing the cycle will stop and
the four-way valve will invert the cycle forcing the machine
to
operate in cooling mode. Defrost cycle
is automatic and does not require any setting.
3.5.14 Control of an auxiliary boiler
This function, as well as the control of the electric heating
elements, is not possible if the machine is configured as
Slave.
NXH units can manage an alternative source of heat such as a
boiler, by controlling its start-up. When the boiler is in ope-
ration the unit is stopped.
Boiler can be activated when:
• The unit is in heating mode but it is stopped due to an
error.
• The unit is in heating mode but the outdoor air tempera-
ture is too low. Usually, the set threshold value is -10_K but
it can be configured from the HCCONFIG menu.
3.5.15 Master/Slave unit
Two Pr can be connected together in a Master-
Slave unit system. The two controls communica-
te through the CCN bus. Configuration parameters are
accessible only from the SERVICE menu requiring the inter-
vention of the Technical Support Service.
The Master-Slave system requires a cascading probe for each
machine to be connected to the piping coming out of the system.
The system can manage pumps with fixed and variable flow
rate; for units with variable flow rate pump, each unit con-
trols its pump according to the required load.
If fixed flow rate pumps are used instead, these are always
running even when the system has a load request. It is pos-
sible to have the Master unit to manage one system pump: in
this case the Slave machine pump is not used.
All checks and settings will be performed on the Master ma-
chine that will transmit the information to the Slave.
The Master can be controlled from the unit panel, remote pa-
nel or CCN system. If the Master is controlled from remote
panel, use dry contacts to turn system on and off.
One of the Master-Slave functions allows establishing
not only which one is the Master and which one is the
Slave unit, but also inverting the roles if the operating
hours of the two units are a lot different. The system, if
configured, will try to keep the operating hours of both ma-
chines identical.
Should the system not be configured as described above, the
machine chosen as Master will always remain that way. The
Master machine always starts first, until it reaches its full ca-
pacity.
Now a countdown starts for the Slave machi-
ne that will be started once countdown is over.
The water setpoint used by the Slave machine is
the same of the Master machine.
During cascading operation, the Master will always
work to its full capacity if the Salve is running, other-
wise it can modulate its operation according to the
system request. In case of communication error
between Master and Slave, the two units will carry on wor-
king as separate machines, using the programming set from
each control panel.
If the Master shuts down due to an error, then the Slave will
start regardless of the Master enabling signal.
For NXH machines in Master-Slave configuration or equip-
ped with at least one additional electric heating element,
the control must be on the entering water temperature.
