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1.1 FOREWORD.
The Star 55 model is a vertical ventilated cooling display cabinet at negative temperature
and it is suitable for preserving ice-creams and frozen food at the temperature of -18°C (-0.4
F). Thanks to the internal ventilation system, this machine performs automatically periodical
defrostings of the evaporator and therefore, it does not need maintenance.
The defrosting system, operated by means of an electrical heater, guarantees best
performances with low current consumption.
A system consisting of two neon tubes positioned in the inner tank, lights the product
preserved internally, by enhancing its characteristics.
An illuminated display, at the top of the cabinet, highlights the brand name.
1.2 DESCRIPTION OF THE SYSTEM OPERATION
Picture 1is showing the exploded drawing of the refrigerator. In the following description
every component will be identified by its number on the exploded drawing and by its code on
the wiring diagram at section 5.1.
1.2.1 THERMODYNAMIC CYCLE
The refrigerating cycle used by Star 55 is by gas compression. Here are the main
components, described on the exploded drawing and on the wiring diagrams SE0211/06 on
section 5.1:
- Compressor (CO) (12);
- Condenser (14) with relative motor fan (MC) (38) and blade (41);
- Dryer (21);
- Refrigerant flow (cut off) valve (VM) (84) with solenoid coil (2);
- Capillary tube;
- Evaporator (20) with relative motor fan (MI) (39) and blade (40);
- Liquid splitter with heat exchanger.
The refrigerant used is R404a, CFC and HCFC free.
1.2.2 STARTING PHASE
To protect the compressor (CO) (10) from heat overloads during the phase following the
refrigerator start-up, the operation of the internal motor fan (MI) (39) is delayed by a fixed
calibration thermostat (KFS) (5) positioned on the evaporator, whose function is also that of
limiting temperature during the defrosting phase; therefore, before the operation of the inside
motor fan, it is necessary that the evaporator lowers its temperature until the thermostat
(KFS) (5) starts the internal motor fan. This operation could take about fifteen minutes.
1.2.3 COOLING PHASE: TEMPERATURE ADJUSTMENT
The internal temperature adjustment is made by an adjustable thermostat (TC) (80),
positioned on the front control panel (18), that acts
on the cut-off valve (VM) (84) solenoid coil (2):
this valve has the function to trap the refrigerant
in the condenser, by closing the access to the
capillary tube and stopping the refrigerant flow to
the evaporator. When the internal temperature
reaches the desired value, set by the thermostat,
the cut-off valve closes and the compressor
reduces the evaporator pressure, till the low
pressure control pressostat (PBP) (88) stops it and
contemporary the condenser motor fan (MC) (38)
- 4 -
L.P. Pressostat
Cut-off valve
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