Page 21
English
6
CONTROL
The standard equipment of the units includes a con-
trol and monitoring electronic system, which ensures
the deployment of all control, monitoring and alarm
functions of these units.
6.1 General information
The system consists of an electronic card and a pan-
el terminal.
Control functions:
h
Checking of the heating/cooling capacity of the
unit.
h
Management of the compressors’ delayed start-
up.
h
Defrosting (CLH models).
h
Antifreeze protection.
h
Pump control (internal hydronic kit)
6.2 Control system
h
Temperature regulation
The regulator mounted on the units (COOLING ON-
LY version) is shop-calibrated to check the unit, as a
function of the temperature of the chilled water back
from the plant.
Its sensor is then installed on the water inlet in the re-
frigerant/water heat exchanger, so that it can mea-
sure the plant load.
The only regulation required for the regulator is the
calibration of the set point, in the +7 to +20 °C
range (the shop calibration is +10 °C).
In case of HEAT PUMP units, the regulator can be
calibrated in the +20 to +47 °C range for heating
(the shop calibration is +40 °C); as for cooling, refer
to the data provided for the cooling only version.
If you wish to set the set point of the enter-
ing water temperature to values below +9
°C, consult our Technical Dept. to learn all
the precautions required to obtain the ideal
operation of the appliance. Anyway, con-
sider always the _T between water inlet and
water outlet, so as not to exceed the mini-
mum temperature of the produced water.
h
Antifreeze functions
These units are provided with antifreeze protection
for the chilled fluid. This protection consists of a resis-
tor in contact wit the refrigerant/fluid heat exchang-
er, which is enabled (also when the unit is off) when
the fluid temperature drops below 5 °C: standard
value for non-glycoled units. The activation of the an-
tifreeze protection causes the safety stop of the in-
volved circuit.
This safety device supplements the action of the dif-
ferential safety pressure switch (glycoled). An an-
tifreeze alarm is activated. If the circulating fluid is
water, before the beginning of winter it is advisable
to drain the circuit to prevent the icing of the water
inside it.
If the circuit cannot be drained, it is imperative to
deenergise the unit, so as to allow, when necessary,
the activation of the antifreeze protection.
h
Defrosting
The CLH heat pump units are provided with an auto-
matic defrosting system that prevents the formation of
excess ice on the refrigerant/air heat exchanger dur-
ing heat pump operation.
This system, which is part of the electronic control
system, is of the time /temperature type, and when
the temperature measured by a sensor at the inlet of
the coil, once the preset time has expired, drops be-
low a pre-determined value, switches the operation
of the unit from heating to cooling.
During the defrosting cycle the compressor works
normally, but the fans of the external coil remain off.
The defrosting cycle stops after the coil has been de-
frosted; at this point the unit works in heating made
again.
Both circuits are defrosted at the same time. For safe-
ty reasons, if the delivery pressure reaches consider-
able values, fans are started also during defrosting.
Control
Manuale CLS-CLH1 7.2.2005 10:17 Pagina 21
